Protein-protein interactions play a key role in cellular signaling, involved in various biological processes. Studies on these interactions are therefore crucial toward understanding the regulatory networks of cellular signaling. It is a standard practice that the protein-protein interactions identified by the yeast two-hybrid system should be independently confirmed by in vitro and in vivo approaches. Pull-down and co-immunoprecipitation (Co-IP) are routine approaches to detect protein-protein interactions. Pull-down assay is used to detect direct or physical interactions between proteins in vitro. In plant biology studies, one of the most convenient methods to detect protein-protein interactions is the transient expression of the target proteins in Nicotiana benthamiana leaves followed by the Co-IP assay. In this paper, we describe the principles and protocols for the GST tag-based pull-down assay and the Co-IP assay of proteins transiently expressed in N. benthamiana leaves, providing a reference for detecting plant protein-protein interactions.

Protein-Protein interactions play important roles in various eukaryotic biological processes. Compared to other techniques measuring protein-protein interactions in plants, the Luciferase Complementation Assay (LCA), based on Agrobacterium-mediated transient expression in Nicotiana benthamiana, is a simple, sensitive, reliable, highly quantitative and low background method that can be easily scaled up for high-throughput interactome studies. Here, we describe a protocol that includes two alternative data collection methods to qualitative and quantitative analyse luminescence or luminous intensity to detect protein-protein interactions in plant cells.

Chinese researchers in plant sciences published more original papers in international top journals and mainstream journals of plant science than last year, and made remarkable achievements in several areas. Research on the supramolecular structure and function of diatom photosynthetic membrane proteins was selected in the top 10 achievements in Chinese Sciences in 2019 and the top achievements of Chinese Life Sciences in 2019. Research on the structure and function of plant disease-resistant bodies was selected in the top 10 achievements of Chinese Life Sciences in 2019. In this review, we provide a commentary on the significant progress made by Chinese researchers in plant sciences this year.

Ubiquitin activating enzyme (E1), ubiquitin conjugating enzyme (E2) and ubiquitin protein ligase (E3) are the key enzymes of ubiquitin modification of substrate proteins. There are large amounts of genes encoding these ubiquitination enzymes in all eukaryotic genomes. Analyzing the biochemical characteristics and specificity of these enzymes and their substrate proteins is important for their functional study. Here we describe a simple and fast method for in vitro ubiquitination assay. In the presence of E1 and ubiquitin, E2 activity can be determined by detecting the DTT-sensitive thio-ester formation. The E3 activity of a putative protein as well as the E2-E3 or E3-substrate specificities can also be explored by in vitro ubiquitination assay. This system is mainiy based on proteins from Arabidopsis, which includes most varieties of Arabidopsis E2 proteins that are tested with several RING-finger type E3 ligases. This system facilitate not only the exploration of E3 activity in combination with various Arabidopsis E2 members but also the study of E2-RING E3 and RING E3-substrate specificities. This system is suitable for the ubiquitination assays of eukaryotic proteins, especially for plant proteins.

Protein phosphorylation is one of the important protein posttranslational modifications that is involved in the regulation of most cellular processes in plants. Protein kinases catalyze the phosphorylation by transferring the phosphate group in ATP to the substrate proteins. The phosphate is usually covalently linked to the hydroxyl group of specific amino acid residues in the substrates by an ester bond. The mostly studied phosphorylation sites are serine, threonine, and tyrosine residues. Here, we present protocols and related tips for the in vitro and in vivo protein phosphorylation assays.

Genome-wide association study (GWAS) is a general approach for unraveling genetic variations associated with complex traits in both animals and plants. The development of high-throughput genotyping has greatly boosted the development and application of GWAS. GWAS is not only used to identify genes/loci contributing to specific traits from diversenatural populations with high-resolution genome-wide markers, it also systematically reveals the genetic architecture underlying complex traits. During recent years, GWAS has successfully detected a large number of QTLs and candidate genes associated with various traits in plants including Arabidopsis, rice, wheat, soybean and maize. All these findings provided candidate genes controlling the traits and theoretical basis for breeding of high-yield and high-quality varieties. Here we review the methods, the factors affecting the power, and a data analysis pipeline of GWAS to provide reference for relevant research.

Transcription affects the growth and development of plants through regulating the spatio-temporal expression of downstream genes. The interaction between transcription factors and DNA is a key section in the process of exploring transcriptional regulatory networks. In the past few years, researchers utilize yeast one hybrid (Y1H) and electrophoresis mobility shift assay (EMSA) to examine whether a transcription factor directly interacts with target DNA. In addition, transient luciferase activity assay provides a convenient method for researchers to test the regulation of transcription factors on downstream gene expression. In this paper, we elaborate the principles, methods, and advantages and limitations of Y1H, EMSA and transient luciferase activity assay, to provide technical references for exploring the transcription factor-DNA interactions.

Recent advances in genomics technologies have greatly accelerated the progress in both fundamental plant science and applied breeding research. Concurrently, high-throughput plant phenotyping is becoming widely adopted in the plant research, promising to alleviate the phenotypic bottleneck. Plant phenomics is a science that studies the growth, performance and composition of plants. It can effectively track the relationship among genotypes, environmental factors, and phenotypes. It is a key research field to break through the future crop research and application. In this paper, three stages of plant phenotypic analysis are discussed, that is, from the initial stage of manual measurement and counting and the assistant stage of specific measurement tools to the stage of high throughput phenomics. It is proposed that the development of plant phenotypic acquisition and analysis is driven by three important factors: phenotypic research facilities, phenotype acquisition technology and image analysis methods. Finally, the plant phenomic research is prospected.

The UPS (ubiquitination/proteasome system) plays a vital role in nearly all plant signaling processes, for example, jasmonic acid receptor COI1 (coronotine insensitive protein 1) and auxin receptor TIR1 (transport inhibitor response 1) are F-box type E3s ligases, and they promote the ubiquitination then degradation of specific transcriptional repressors through 26S proteasome to activate hormone signaling. However, for the whole UPS system, only a few E3 ligase/substrate pairs’ interactions have been demonstrated due to technical limitations in plants. Generally, E3 ligase and substrate are expressed in Escherichia coli for ubiquitination assay, which may lack post-translational modifications that are important for protein function, then gives false negative result. We describe a quick and efficient assay for detecting E3-mediated protein ubiquitination in vivo by means of agroinfiltration for transient expression of relevant genes in tobacco (Nicotiana benthamiana) leaves. In detail, this method can detect the specific interaction between E3 ligase and substrate, substrate ubiquitination, the effect of E3 ligase on degradation of its substrate, inhibition of substrate degradation by 26S proteasome inhibitor MG132, and in vitro ubiquitination assay with endogenous plant proteins.

Increasing plant density is an important approach to boost crop yield, and leaf angle is one of the key factors affecting plant density. Recently, Feng Tian’s lab from China Agricultural University cloned and characterized two major QTLs (UPA1 and UPA2) regulating leaf angle in maize. The underlying genes are brd1 and ZmRAVL1, respectively, and both of them are involved in the brassinosteroid (BR) pathway to regulate leaf angle. UPA2 is located 9.5 kb upstream of ZmRAVL1 and is bound by DRL1. LG1, another leaf angle protein, directly activates the expression of ZmRAVL1. DRL1 and LG1 physically interact and the resulting complex in turn represses the LG1-activated expression of ZmRAVL1. The teosinte allele of UPA2 has a higher binding affinity with DRL1, resulting in the reduced ZmRAVL1 expression, which consequently down-regulates the brd1 expression and leads to the decreased brassinosteroid level, thereby reducing the leaf angle. The introgression of UPA2 teosinte allele into maize and the manipulation of ZmRAVL1 significantly increase maize yield with increased plant density. These findings have paved a new avenue for molecular breeding of high-yield maize varieties.

In 2020, the numbers of original research articles published by Chinese plant scientists in international multidisciplinary journals and mainstream plant science journals increased significantly compared with that in 2019, and important advances have been made in the fields of plant development, stress tolerance, crop biology, genomic phylogenetics and evolution. Among them, “Cloning, functional characterization and application in wheat breeding of the Fhb7 resistant gene to Fusarium head blight”, and “A new mechanism to improve the nitrogen-utilization efficiency in crops” were selected as two of the “Top Ten Advances in Life Sciences in China” in 2020. Here we summarize the achievements of plant science research in China in 2020, and briefly introduce 30 representative important research advances, so as to help readers understand the developmental trend of plant sciences in China, and conduct their future research to meet the national needs.

In order to adapt to various living environments, plants have gradually evolved a complex immune system against the infections caused by pathogens. The nucleotide-bounding leucine-rich repeat proteins (NLRs) act as typical resistance (R) proteins which commonly exist in plants and play an important role in regulating plant disease resistance. In this paper, the research progress of NLRs is reviewed from the aspects of NLR protein structures, signal transductions and regulations of plant disease resistance.

SUMOylation, a post-translational modification, is essential for plant normal growth and development. To date, thousands of possible SUMO substrates have been identified, but due to the relatively low SUMOylation level, biological significance of the SUMOylation remains largely unknown. Here, we summarized the SUMOylation detection methods, including in vitro and in vivo SUMOylation assays, which help to understand the functions of SUMOylation in plants.

Under field conditions, biotic and abiotic stresses usually occur simultaneously, and threaten global food security. Uncovering the mechanisms underlying plant response to combinations of two or more stress conditions holds the potential to breed new crop varieties with enhanced stress tolerance. Recent studies have revealed that the response of plants to stress combinations is unique and cannot be directly extrapolated from the response of plants to each of the different stresses. The responses of plants to different combined stresses might integrate with different signaling pathways at multiple levels, including defence responses, transcription factors, hormone signaling and osmolyte biosynthesis. Here, we review the molecular and physiological responses and adaptations of plants to different stress combinations, and provide an update on multi-omics approaches to study combined stresses.

Plant secondary cell walls (SCWs) contain cellulose, hemicellulose and lignin, which endow the cell walls with mechanical strength and hydrophobicity. This characteristic is very important for plant upright growth, water and nutrient transport, and resistance to biotic and abiotic stresses. In this review, we summarize the transcription factors regulating SCW biosynthesis and their regulatory mechanisms, including NAC transcription factors functioning as first-layer master switch, the AtMYB46/AtMYB83 and their downstream regulators serving as secondary-layer master switch, as well as the other transcription factors involved in the regulation of biosynthesis of the SCW. The future research contents and methods are also prospected in order to provide reference for further research on the transcriptional regulatory network of SCW biosynthesis.

Plant growth and development are affected by various environmental factors. In response to various environmental changes, plants have evolved a series of signal recognition and transduction proteins, such as the plasma membrane-localized receptor-like kinases (RLKs), to cope with the environmental conditions. The lectin receptor-like kinases (LecRLKs) are a subfamily of RLKs that contain three structural domains: the extracellular lectin domain, transmembrane domain, and the intracellular kinase domain. Based on the structural difference of the extracellular lectin domain, LecRLKs are classified into three subclasses: L-, G-, and C-type. Recent studies have shown that LecRLKs play a vital role in plant development and biotic/abiotic stress responses. In this review, we discribe the research history, structural features and classification, and biological functions of LecRLKs, and emphasize on the functions of LecRLKs in plants in response to biotic/abiotic stresses and in regulating development. This review provides a view for future functional study on LecRLKs and crop improvement by elaborating different types and functions of LecRLKs.

Low temperature, drought, high salt, hypoxia and other adverse environmental changes affect plant growth and development. Plants adapt to these adverse conditions through the development of complex regulatory mechanisms during long-term evolution. APETALA2/ethylene responsive factor (AP2/ERF) is a plant-specific transcription factor that plays a key regulatory role in various stress responses. In recent years, more and more studies have shown that plant hormone-mediated signaling is closely related to stress responses, and AP2/ERF transcription factor and hormone signal transduction form a cross-regulatory network. Many AP2/ERF transcription factors respond to plant hormones abscisic acid (ABA) and ethylene (ET), activating the expression of stress response genes that are dependent on and independent of ABA and ET. In addition, AP2/ERF transcription factors are also involved in gibberellin (GA), cytokinin (CTK) and brassinsteroid (BR) mediated growth and developmental processes and stress responses. This paper briefly reviews the research progress of AP2/ERF transcription factors in term of structure, transcriptional regulation, posttranslational modifications, binding sites and interacting proteins as well as its transduction pathways involved in hormone dependent- or independent- regulation of the abiotic stress responses, which will provide the basis for further understanding the roles of different AP2/ERF transcription factors in the regulation of hormone and stress response network in plants.

The Green Revolution represented by the breeding of semi-dwarf crops greatly promoted agriculture yield, but it also unfortunately led to the problem of low nitrogen use efficiency (NUE). The achievement of Green Revolution was mainly based on modification of gibberellin (GA) metabolic or signaling pathways in crops. A previous study has found that the central regulator of GA signaling pathway DELLA protein negatively regulates NUE through suppressing GRF4, an essential NUE regulator, which provided a resolution for improving NUE of semi-dwarf rice. A recent study further revealed a novel mechanism underlying the crosstalk between GA signaling and nitrogen response. The study revealed that NGR5 is a key gene controlling tiller number changes under different nitrogen conditions, which is inducible by nitrogen. Further investigation established that the NGR5 suppresses branching inhibitory genes, such as D14 and OsSPL14, through nitrogen-dependent recruitment of polycomb repressive complex 2 that promotes histone H3 lysine 27 tri-methylation in the regions habouring the branching suppressors. In addition to be responsive to nitrogen, NGR5 is also negatively regulated by GA and its receptor GID, and overexpression of NGR5 in the semi-dwarf background is thus able to significantly improve rice yields under low nitrogen conditions. This study not only uncovered a new mechanism of GA signaling, but also enlightens the new generation of Green Revolution by breeding high yield crops with enhanced NUE.

Rice is the most important crop in the world. However, rice blast caused by Magnaporthe oryzae and sheath blight caused by Rhizoctonia solani are two of diseases, which threaten both yield and quality of rice most severely. To ensure food security, it is very important to identify disease-resistant rice germplasm, clone disease resistant genes, uncover the molecular basis and apply them in rice breeding program. Accurate evaluation of the disease resistance of rice is fundamental to both uncover disease resistance mechanism and improve resistance in rice breeding. Here, we describe the common methods for evaluating rice blast disease resistance by spraying inoculation of seedlings with M. oryzae, injection inoculation at rice tillering and booting stage, and punch inoculation of detached rice leaves. We also describe the methods for evaluating rice sheath blight disease resistance by field inoculation with R. solani at rice tillering stage, greenhouse inoculation at rice booting stage, and inoculation of rice detached-stems in growth chamber. We believe these methods could provide useful protocols for colleagues who aim to identify rice disease-resistant resources, dissect the underlying molecular mechanism and breed elite rice varieties with improved disease resistance.

Phytohormones are important regulatory substances for plant growth, directly or indirectly functioning in various developmental stages, from seed germination to maturity, as well as numerous biotic/abiotic stresses response. With the continuous improvement of small molecular compounds used to explore the molecular mechanisms of physiology and metabolism, chemical biology, a new frontier interdisciplinary discipline between plant biology and chemistry, was coined, and the important progresses have been achieved in a short time in the past several years. It has been revealed that the ideas and methods of chemical biology play an irreplaceable role in the research of plant hormones, especially in the area of plant signal transduction. This review summarizes the published small molecular analogs of major plant hormones, and outlines the mechanisms of how these small molecular analogs function in plant growth and development, and in response to biotic/abiotic stresses. Finally, the potential applications of these analogs in agricultural practice and future research directions were discussed.

The superfamily of ABC (ATP-binding cassette) transporters, which contains eight subfamilies from ABCA to ABCH, has diverse structures and complex functions. ABCB transporters, are mostly located in the plasma membrane, while others are located in the mitochondrial membrane or chloroplast membrane. ABCB transporters, together with AUX1/LAX (AUXIN1/LIKE AUXIN) and PIN (PIN-FORMED), coordinate and participate in the polar transport of auxin, and play an important role in regulating plant growth and development. ABCB transporters also function in plant tropism and resistance to heavy metals. In recent years, with the completion of whole-genome sequencing in different plants, research on ABCB genes is no longer confined to the model plant Arabidopsis thaliana, rather, preliminary studies have been carried out to explore the functions of ABCB genes in cereal including rice, maize, and sorghum. However, the functions for most of the plant ABCB transporters remain elusive. Here we reviewed the research progress and future development of ABCB subfamily transporters in Arabidopsis and cereal, in the hope of providing clues for fully revealing biofunctions of the ABCB subfamily.

Plants have evolved to maintain the dormancy of freshly harvested seeds, which ensures that seeds do not germinate until environmental conditions are optimal. Therefore, dormancy helps seeds spread over long distances to ensure the survival of species. The transition from dormancy to germination is crucial to plant survival and for promoting yield and quality in agricultural production. Seed dormancy and germination are precisely regulated by diverse endogenous hormones and light signals. Light cues regulate seed dormancy and germination by affecting abscisic acid/gibberellic acid biosynthesis and signals. In this review, we summarize the key roles of the hormone pathway and light signal transduction pathways in regulating seed dormancy and germination. We also discuss the interactions (crosstalk) between phytohormone signals and light signals in seed dormancy and germination, in order to apply reference for regulating seed dormancy and germination by using light and hormones in agricultural production.

Soybean is one of the most important crops for food and oil. With the increasing demand in recent years, China has imported more and more soybean from abroad. Enlarging the planting area and improving the yield per hectare are effective ways to increase the soybean production. Northwest of China, especially Xinjiang has the potential of enlarging the planting area and improving the yield per hectare for soybean production in China. This paper analyzes the feasibility of developing soybean production in Xinjiang from the aspects of the natural climatic conditions of soybean production, the planting situation of soybean, and the advantages and limitations of developing soybean production in Xinjiang. Then, it provides suggestions for future development of soybean production in Xinjiang on policy support, improvement of mechanization level, accelerating scientific and technological innovation to cultivate elite varieties, and strengthening soybean production demonstration.

Plants initially sense microbes via perception of pathogen associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs) located on the cell surface. This recognition is referred to as PAMP-triggered immunity (PTI). In order to ensure their physiological and cellular functions, PRRs must be properly conveyed from their site of synthesis, i.e., the endoplasmic reticulum, to their final destination, the plasma membrane (PM), through the secretory pathway. PRRs also rely on recycling and/or degradation, two processes that are initiated by endocytosis. Intracellular trafficking serves to terminate signaling through degradation, sustains signaling through recycling, or relays signaling inside the cell through the formation of signaling endosomes. In this review, we summarize the current knowledge of plant PRRs and their ligands, illustrating that intracellular trafficking plays an important role in plant immunity.

Because of the fixed growth habits lacking of mobility, plants have innovated unique strategies to cope with variable environmental conditions. For their survival, plants have evolved mechanisms of stress memories to adapt to the adverse environments and thus protect themselves. Epigenetic modifications not only regulate the growth and development of plants, but also participate in responses to various abiotic and/or biotic stresses. Recent studies have shown that epigenetic modifications play important roles in the control of plant stress memory. In particular, DNA methylation, histone methylation, histone acetylation modification, and other modifications are involved in the formation and the maintenance of specific stress memories. This review highlights the recent advances of plant stress memories mediated by epigenetic modifications, and some key challenges in this field were discussed.

Terpenoids are the most abundant structural and quantitative compounds in plant secondary metabolites, and they play an important role in the interaction of plants with the external environment. Transcription factors have the function of regulating the expression level of genes in the secondary metabolic pathway and regulating the production of secondary metabolites. In the last decades, there are six major transcription factor families involved in the terpenoids biosynthesis (AP2/ERF, bHLH, MYB, NAC, WRKY and bZIP). In this study, we reviewed the structure characteristics, regulatory mode, and research advances of several important transcription factor families in the plant terpenoids biosynthesis, and hope to further enrich the regulatory network of terpenoids synthesis, and provide a reference for molecular breeding, high-quality cultivation and biological control in relevant to terpenoid biosynthesis.

Meiosis halves the number of chromosomes to produce haploid gametes through nuclear division twice following single round of DNA replication, and is essential for eukaryotic sexual reproduction. Arabidopsis thaliana is a traditional model organism used for molecular genetic study. Recently, with breakthroughs in microscopic technologies for observing chromosomes, analyses of chromosome morphology during meiosis using cytological methods have made great advances to understand molecular and genetic mechanisms in regulation of meiosis. In this study, we described in detail the chromosome spread technique we developed, which is well used for observation of chromosome behaviors in Arabidopsis male meiocytes.

Abscisic acid (ABA) plays important roles in regulating plant growth and development, and in responding rapidly to various environmental stimuli. The endogenous ABA level in plants is regulated sophisticatedly by the ABA biosynthesis, catabolism, and transportation pathways. This paper reviewed the most recent advancements in ABA de novo biosynthesis, ABA hydroxylation catabolism, reversible glycosylation metabolism, and ABA transportation pathway in plants, with emphasis on the expression regulation mechanism of the ABA biosynthetic and catabolic genes. Prospectives for research directions in the future were also suggested.

Macroautophagy (hereafter termed autophagy) is an evolutionarily conserved cellular degradation and recyc- ling pathway in eukaryotes. In this pathway, cellular substances, such as dysfunctional proteins and damaged organelles, are sequestered by a double-membrane structure, autophagosome, and eventually delivered to the lysosomes or vacuoles for degradation and recycling. Autophagy plays essential roles in plant growth and development, as well as in response to environmental stresses. Up to now, more than 40 autophagy-related (ATG) genes have been identified in model plants such as Arabidopsis thaliana and Oryza sativa. It is well established that a large number of ATG genes are up-regulated during specific developmental stages such as leaf senescence and seed maturation, as well as when plants encounter adverse environmental conditions, for example, nutrient starvation, drought or pathogens infection and so on. However, the transcriptional activation or repression mechanisms of ATG genes during these biological processes are largely unknown and need further study. In this review, we summarized the roles and the well-established transcriptional regulation network of ATG genes during plant growth, development and stress responses.

Developmentally regulated plasma membrane polypeptide (DREPP) proteins, a family of plant-specific proteins associated with the plasma membrane, have multiple functions such as combining PtdInsP_s, the Ca ²⁺/CaM complex, microtubules and microfilaments. DREPPs play an important role in plant growth and development and response to stress (e.g., low temperature and drought). This paper reviews the composition of the DREPP family as well as their protein sequence characteristics and biological functions during development and stress response and provides information for understanding how DREPPs mediate signaling networks.

It is well-known that DELLA, AUX/IAA, JAZ and D53/SMXL act as repressor proteins that bind and repress transcription factors to suppress expression of hormone-responsive genes, while hormone molecules trigger signal transduction to induce degradation of these repressor proteins and eventually activate expression of hormone-responsive genes essential for various biological processes. The research team led by Dr. Jiayang Li recently reported that SMXL6, SMXL7 and SMXL8 (SMXL6,7,8) in strigolactone (SL) signaling pathway serve as dual-function repressor proteins which act as both repressors and transcription factors. They found that SMXL6,7,8 can function as transcription factors by directly binding to the promoters of SMXL6,7,8 genes and repressing their expression. In addition, they identified a large number of novel SL-responsive genes, and revealed molecular mechanisms underlying how SL regulates shoot branching, leaf elongation and anthocyanin biosynthesis. These important findings provide new insights into our understanding of plant hormone action, which are scientifically significant and agriculturally important.

According to the Traditional Theory, a carpel (basic unit of angiosperm gynoecium) is derived from a modified leaf or megasporophyll through longitudinal folding and inward enrolling. Unfortunately, this theory introduces an unnegotiable gap between angiosperms and gymnosperms. Different from the Traditional Theory, the Unifying Theory provides a link bridging the gap mentioned above—an angiosperm carpel is derived from the synorganization between an ovule-bearing branch and an enclosing leaf. Recently two papers authored by leading botanists, Peter R. Crane and Peter K. Endress, respectively, expressed their opinions different from the Traditional Theory of angiosperm evolution. Endress stated that a carpel is result of synorganization between foliar part(s) plus ovule(s); and Crane stated that ovules/seeds are borne on the termini of branches. Combining the two, it is easy to infer that a carpel is equivalent to a foliar part plus an ovuliferous branch, a conclusion in line with the core conception of the Unifying Theory. The subtle changes in perspectives of these two leading botanists imply that there will be a major paradigm shift in botany soon. In order to make our botanists aware of the coming-soon changes in plant evolution theory, we summarize the latest progresses in relevant areas.

As one of the plant cell wall polysaccharides, pectin has a very complex structure and function. Pectin is mainly composed by homogalacturonan (HG), rhamngalacturonan I (RGI), rhamngalacturonan II (RGII). Pectin plays an important role in maintaining the integrity of cell wall structure, intercellular adhesion and signal transduction. Therefore, studying the structure, distribution and roles of pectin components is of great significance for understanding the construction and function of cell wall. However, it is not clear how these three components of pectin cross-link to form high structure and perform biological function in the cell wall. This review will focus on the biosynthesis, functions of HG, RGI, RGII as well as the microscopic imaging techniques of pectin, aiming to provide a theoretical basis for the study of the structure and function of plant pectin.

To determine the effect of different hormones on explant browning and callus browning in Cyclocarya paliurus, leaf browning was controlled on medium with different kinds and content of hormones (6-BA, GA₃, NAA) by a single-factor completely random test. Callus browning was controlled on the medium with different content of 6-BA+NAA and different basic medium by a double- and single-factor completely random test, respectively. The rate of leaf browning reached 0, and the rate of callus induction was up to 100% on the improved MS medium with 1.0 mg∙L ^-1 6-BA and 1.0 mg∙L ^-1 GA₃ and 0.3 mg∙L ^-1 NAA. The rate of callus browning reached 0, and the callus propagation was up to 4.80 times on the improved MS medium with 0.5 mg∙L ^-1 6-BA and 0.2 mg∙L ^-1NAA. The callus was yellow with green or yellow, granular, small and compact, hard and dry. This system effectively solved the problem of leaf browning and callus browning and provided a simple and effective way for tissue culture and a solid foundation for the regeneration system from leaf of C. paliurus.

Scales are epidermal appendages on the rhizomes and leaves of many ferns. Features of scales play an important role in classification of ferns. The phylogenetic position and delimitation of Pteridaceae were treated differently by different authors. Here we collected scales of 76 fern species in Pteridaceae, and observed them under a dissecting microscope. By comparing the morphological characters, we found that scales are different among genus and subfamilies. We reconstructed a phylogenetic tree with the plastid rbcL sequence of the species in this study downloaded from GenBank database and reconstruced the ancestral state for two selected characters (margin of the scale and mesh type). The results suggested that homogeneous scale and entire margin were plesiomorphic characters, while non-entire margin and transparent mesh were evolved late in evolutionary process. We also speculated that the formation of transparent or non-transparent mesh may relate to the light intensity in the habitats.

MicroRNA (miRNA), a kind of regulatory non-coding small RNA, induces degradation of target mRNA or inhibits its translation by specific or non-specific binding, thereby regulating plant growth and development. AP2, the target of miR172, encodes transcription factors that are unique to plants. miR172 regulates the expression of AP2 at the post-transcriptional or translational levels, thus regulating plant floral development, phase transition, spikelet morphology, tuber and fruit development, nodulation in legumes and stress response. Here we summarize the recent advances in the regulation of plant growth and development by miR172-AP2 regulatory module.

Drought stress induces the response of wheat roots, which simultaneously send signals to the aboveground parts stimulating physiological reactions in the aboveground parts, and thus improving drought tolerance of plants. Root architecture traits include morphological traits and three-dimensional geometric structures (i.e, topological structures). The root system architecture not only has genetic stability, but also shows plasticity. The root physiological and biochemical responses to drought stress primarily involve in induced production and changes of root-sourced chemical signals, root cell enzymes, and root osmosis. Under drought stress, plants also alter root anatomical traits and water-uptake kinetics. In this paper, current advances in the studies on root responses to drought stress of wheat (Triticum aestivum) were reviewed with a focus on root system architecture traits, root physiological properties and root anatomical characteristics. The relationship between wheat root properties and drought stress, and the current research constrains were discussed. This review would provide a guidance for future studies on wheat root traits in response to drought stress.

Vesicle trafficking is the biological process involving in budding, translocation, tethering and membrane fusion in all eukaryotic cells. Nine multisubunit tethering complexes (MTCs) are known to play roles in the intracellular transport, and the exocyst complex facilitates the tethering between transport vesicles and the plasma membrane (PM). The regulatory mechanism of the exocyst complex had been extensively studied in yeast and animals, whereas rapid research progress on plant exocyst has been made in recent years. Recent findings show that the plant exocyst complex has unique regulatory characteristics and is widely involved in plant growth, development and stress responses. Here we summarize research progress on the plant exocyst complex to provide a reference for future study of exocyst function in plants.

RNAs can be classified into protein-coding RNAs and non-coding RNAs (ncRNAs). Small non-coding RNAs (sRNAs) are generated by Dicer-LIKEs (DCLs) and RNA Dependent RNA Polymerases (RDRs). They are associated with different ARGONAUTE (AGO) effector complexes and play important regulatory roles in diverse biological processes. 21 nt microRNAs (miRNAs) and 24 nt small interfering RNAs (siRNAs) are the most abundant classes of sRNAs in plants. The mechanisms of their biogenesis and functions are well studied. However, the functions of other less abundant sRNAs remain largely unknown. A recent study from Prof. Hongwei Guo's group at Southern University of Science and Technology showed that a class of 22 nt siRNAs is produced by RDR6 and DCL2 when plants are under certain stress conditions, especially upon nitrogen deficiency. These 22 nt siRNAs are loaded into AGO1 and mediate translational repression of target mRNAs including nitrate reductase structural genes NIA1/2, thereby minimizing energy consumption. This work elegantly shows that plants deploy 22 nt siRNAs to achieve a deliberate balance between growth and defense in response to environmental stress.

Senescence is an autonomous and irreversible adaptive response at the end of plant development. The molecular mechanism related to premature senescence of leaves is important for rice genetic improvement and breeding of anti-aging varieties. LS-es1 is a stable hereditary premature early senescence mutant obtained by EMS mutagenesis of indica variety TP309. Phenotypic observation, physiological and biochemical analysis of LS-es1 and its wild type TP309 found that LS-es1 accumulated a large amount of reactive oxygen species and more cell death, while the yield-related agronomic traits of LS-es1 were significantly decreased compared to wild type TP309, which also verified the early senescence characteristics of LS-es1. Exogenous hormone treatment of LS-es1 and TP309 seedlings showed that LS-es1 was more sensitive to salicylic acid (SA), abscisic acid (ABA) and methyl jasmonate (MeJA). The LS-es1 gene was mapped to the 46.2 kb region of the long arm of rice chromosome 7 by map-based cloning, which included 8 open reading frames (ORFs). Bioinformatics analysis of the genes in this interval revealed that two candidate functional genes, Os07g0275300 and Os07g0276000, were associated with the early senescence pathway, and the expression levels of these two genes were significantly different between wild type and mutant. The results laid the foundation for further cloning of the LS-es1 gene and in-depth study of its biological function.