As one of the key factors affecting rice yield, the grain number per panicle has always attracted the attention of breeders. The formation of grain number per panicle is a complex biological process, which is regulated by many genes. According to their impact on phenotype, we roughly divide these genes into three categories: related to the number of branches, related to panicle type and related to spikelet determination. In this paper, we summarized the genetic regulation mechanisms of the grain number per panicle-related genes, and put forth the strategies for their use in high yield breeding of rice.

Systemic acquired resistance (SAR) is a long-lasting broad-spectrum resistance at the whole plant level activated by the primary infection of pathogenic microorganisms at local leaves. The signals generated rapidly at the initial infection site can be transmitted to other parts of the plant through the phloem to activate SAR. Pipecolic acid (Pip) and N-hydroxy-pipecolic acid (NHP), as newly discovered mobile signal molecules, play important roles in SAR signaling pathway. Here, we mainly review the latest research progress in the synthesis, transportation of Pip/NHP and their regulation of SAR.

Rice (Oryza sativa) is a major food crop in the world. The optimization and utilization of the major yield-determining factors are important for increasing yield potential. Among these factors, seed weight is one of the most important factors determining rice production. The heritability of rice grain weight is stable, which is largely unaffected by environmental factors. Grain weight depends on grain shape, which is determined by grain length, grain width, and grain thickness, and the degree of grain filling. The growth of rice glumes and seed endosperm determines the grain shape and weight. The proliferation and expansion of glume cells affect grain development, and endosperm occupies most of the volume of mature seeds. Auxin is an important plant hormone that affects rice yield, which regulates the development of glume and endosperm after fertilization. The spatial-temporal distribution of active auxin is dynamically modulated by auxin metabolism, auxin transport and signal transduction, all of which maintain auxin at the optimal level for seed development. Here we reviewed the research progress of auxin pathways regulating rice grain shape from three aspects, auxin metabolism, auxin transport and auxin signal transduction, to provide clues for exploring the auxin regulation mechanism of grain shape and improve yield in rice.

Auxin polar transport regulates plant growth and development. The polar transport of auxin mainly depends on three transporters: AUX/LAX, PIN and ABCB protein families. The direction of auxin flow between cells is closely related to the polar localization of PIN proteins in cells. The PIN protein contains a central hydrophilic loop (HL) and two separated hydrophobic regions, and the multiple phosphorylation sites on HL are the targets of protein kinases. The PIN proteins are fine-tuned at multiple levels, including transcriptional regulation, post-transcriptional modification, intracellular recycling and vacuolar trafficking for degradation, in response to endogenous and exogenous signals. Using genome-wide analysis, 12, 15 and 11 PIN like genes have been identified in rice, maize and sorghum, respectively, but the functions of only a few genes have been reported. Here we reviewed the research progress of PIN protein in Arabidopsis thalianaand cereal crops from the aspects of protein structure, activity regulation and functional verification to provide new ideas and clues for exploring the auxin polar transport mediated by PIN protein family.

The outer surface of plasma membrane (PM)-localized LORELEI-like glycosylphosphatidylinositol-anchor (LLG) proteins, as the molecular chaperone of CrRLK1Ls family of receptor-like kinase, are involved in the transport of CrRLKs and extracellular signal transduction, regulating plant reproduction, development, as well as immune and stress responses. LLG2/3 interacting with ANX and BUPS regulates pollen tube growth and rupture. LLG1 interacted with FER activates the ROPGEF1-ROP2-NADPH oxidase pathway for ROS production, and then promotes root cell elongation and root hair growth. Besides, LLG1, as co-receptor of FER, interacts with RALFs, and then regulates G protein β (AGB1), PM H ⁺-ATPase activity, as well as the homeostasis of intracellular ROS and Ca ²⁺, for modulating stomata and roots in response to salinity. For immune response, LLG1 interacts with FLS2 and EFR, activating the downstream RbohD for ROS production. This review provides important information for understanding LLG biological functions.

May 4^th 2020 is the 100^th birthday of the then professor Tsunghsing Tsao (Zong-Xun Cao), the founding editor-in-chief of the Chinese Bulletin of Botany. To commemorate this special moment, the author shared some pieces of his memory upon the first meeting with her, the experience of carried on her almost life-long project of study of unisexual flower development in cucumber, and the finding of the logic inconsistency between our experimental observations and traditional interpretation of unisexual flower as a model system to investigate plant sex differentiation. In addition, the author shared some of his thought on what is scientific research, which was intrigued from his unique experience of working with the unisexual flower of cucumber. The thought might provide an alternative view on the issue for the youth who are interested in dedicating into exploration of unknown nature.

Abscisic acid (ABA) plays a key role in the growth, development and stress condition of plants. The process of plant response to ABA is completed by signal recognition, transduction, and response cascades. The core ABA signaling pathway consists of receptor RCAR/PYR/PYLs, phosphatase PP2Cs, kinase SnRK2s, and transcription factors and ion channel proteins. Post-translational modifications (PTMs) of proteins such as phosphorylation, ubiquitination, small ubi- quitin-related modifier (SUMOylation) and redox modifications plays an important role in ABA signaling. This review focused on the role of modifications in the core ABA signaling pathway.

Light is an important environmental factor that affects plant growth and development. Flowering is the most important event in higher plants. Plants perceive accurately changes in the surrounding light environments by photoreceptors, thus activating a series of signaling transduction processes and initiating flowering. Here, we summarized the current understanding of the structural characteristics and physiological functions of various photoreceptors in higher plants. We reviewed the molecular mechanisms of phytochromes, cryptochromes, and FKF1/ZTL/LKP2 in mediating signaling transduction and flowering time, including transcriptional and post-transcriptional regulation of CO and FT. Finally, we described the advances in photoreceptor-mediated-integration of light, temperature, and gibberellin signals in regulating flowering. Future directions in this area were also proposed.

Plant growth and development are easily affected by environmental changes, and epigenetic mechanisms play important roles in regulating gene expression in response to environmental stimuli. In recent years, epigenetic stu- dies have achieved important progress in the response to abiotic stresses in plants, providing a good foundation for further understanding the potential molecular mechanisms. In this review, we summarize the plant epigenetic regulations, including DNA methylation, histone modification, chromatin remodeling and small RNA, in response to abiotic stresses.

Autophagy is a protein degradation pathway in which target cellular materials are delivered to the lysosome and degraded by specific hydrolytic enzymes in animals; this progress is carried out within vacuoles in plants and yeast. Recently, several autophagy-related (ATG) genes have been successfully identified in Arabidopsis. Those genes are essential for autophagosome formation and the regulation of autophagy. Here we summarize the regulation of plant autophagy and its function in the plant adversity response.

Because plants are sessile and photo-autotrophic, they must adapt to the surrounding environment. Auxin is one of the most important plant hormones essential for plant growth and development. Recently, auxin was found to regulate plant growth by responding to endogenous developmental signals and by mediating various environmental cues. In this review, we focus on how auxin regulates plant growth by mediating various environmental cues such as light, temperature, gravity, nutrient element and metal ion signals.

Nitrogen is one of the most important mineral nutrient elements for plant growth and development, playing an essential role in the whole process of plant life. Nitrogen assimilation is a central link for plants to utilize nitrogen and also a factor in low nitrogen use efficiency in plants. It includes two types: assimilation of nitrate (NO3 ^–) and ammonium (NH4 ⁺); the latter is the critical step in the process of nitrogen assimilation. The source of NH⁴
+ during ammonium assimilation can be divided into 2 types—primary assimilation and secondary assimilation—but both proceed in the glutamine/glutamate (GS/GOGAT) pathway. Ammonium assimilation requires much energy resources but also consumes abundant carbon skeletons, so it is strictly regulated at different levels including transcription, post-transcription, and post-translation. We review the current progress in study of ammonium assimilation and its regulatory mechanism in plants.

In the recent 500 years, plant introduction or domestication and internationalization of introduced plant crops have profoundly changed the world agricultural productions and have had far-reaching impacts on the history of human civilization. Whether in Western colonial history or in the Ming and Qing dynasties of China, successful introduction and domestication of important crop plants have immeasurably changed economic and social developments and history. Plant living collections are the core of botanical gardens and the “soul” by inheriting the contexts and achievements of scientific research of modern botanical gardens in the past five centuries. Plant living collections are also a foundation of botanical garden-based life science and biotechnology and supporting facilities for other disciplines and are of fundamental importance for current and future developments of botanical gardens. Living collections of plant-based research in botanical gardens are multi-disciplinary, of critical importance for contemporary basic biology and also closely connected to economic and social prosperity and our daily life.