The domestication of crops was a significant event in human history, which led to the emergence and prosperity of agricultural civilization. Maize is an important global food crop, and its domestication origin has long attracted the attention of both the biological and historical communities. The mainstream view in the past was that modern maize originated from the parviglumis type of teosinte. Recently, Yan Jianbing and his collaborators systematically collected and sorted various types of wild and cultivated maize resources, and comprehensively applied genomics, population genetics, and quantitative genetics methods, along with the use of archaeological findings. They found that modern maize also has the gene introgression of the mexicana type of teosinte, which has influenced many agronomic traits. A new model for the origin of modern maize has been proposed based on these findings.

Auxin plays an important role in plant growth and development and its signal transduction has always been the focus of attention in the field of plant biology. AUXIN BINDING PROTEIN 1 (ABP1)-TRANSMEMBRANE KINASE (TMK) molecular module is involved in the extracellular auxin perception. In recent years, ABP1 has been controversial as an auxin receptor. Recently, Tongda Xu’s team and Zhenbiao Yang’s team from Fujian Agriculture and Forestry University identified ABP1-LIKE PROTEIN (ABL) as the auxin binding proteins involved in the extracellular auxin perception. Different from traditional functional redundancy, ABL and ABP1 achieve functional compensation effect through protein structure similarity, and then form complex with TMK at the plasma membrane, acting as co-receptors of apoplastic auxin to mediate auxin driven rapid response. This study deeply dissects the mechanism of extracellular auxin sensing, which is a breakthrough in the field of auxin signaling transduction.

Plants can coordinate the growth direction of their various organs upon the gravity stimulus. In the process of plant gravitropism, gravity sensing and gravity signal transduction have always been the focus of attention in the field of plants. The classical “starch-statolith” hypothesis proposes that plants sense gravity through the sedimentation of amyloplasts that contain starch granules. In addition, previous studies have shown that LAZY proteins regulate plant gravitropism by mediating the asymmetric distribution of auxin. However, the molecular mechanism underlying how sedimentation of amyloplasts triggers gravity signal transduction and its coordination with LAZY proteins remains unclear. Recently, Professor Haodong Chen’s team from Tsinghua University reveals that gravistimulation induces the phosphorylation of LAZY proteins via MKK5-MPK3 kinase pathway in Arabidopsis, which modulates the phosphorylation of LAZY proteins. The phosphorylated LAZY proteins can enhance their interaction with the TOC proteins on the surface of amyloplasts, leading to the enrichment of LAZY proteins on the surface of amyloplasts and the polarity relocation on the new bottom of plasma membrane. This study illustrates the molecular mechanism underlying gravity signal transduction in plants and establishes the molecular connection between gravity sensing and LAZY mediated auxin asymmetric distribution, which is a major breakthrough in the field of plant gravitropism.

Aphids and the viruses transmitted by them cause some of the most devastating plant diseases across the globe. Once infected by aphids, plants can produce and release volatile organic compounds (VOCs), which are transmitted through air and elicit defense in neighboring plants (airborne defense, AD). However, the mechanisms underlying AD remained largely elusive. Dr. Yule Liu’s group at Tsinghua University, China, recently reports a new study and they identify a new signaling circuit, comprising methyl-salicylate (MeSA), salicylic-acid (SA)-binding protein-2 (SABP2), a transcription factor NAC2 and SA-carboxylmethyltransferase-1 (SAMT1) converting SA to MeSA, that mediate interplant communication and airborne defense against aphids and viruses. Furthermore, some virus-encoded virulence proteins could interact with NAC2 transcription factor to reduce the nuclear localization and promotes the degradation of NAC2, thereby suppressing the interplant AD and promoting viral transmission. This comprehensive study provides new mechanistic insights into airborne defense of plants and unravels an amazing aphid/virus co-evolutionary mutualism. It also sets the foundation for new approaches of using AD to control aphid and virus diseases in agriculturally-important plants.

Crop production is constantly threatened by various insect pests, revealing the mechanism underlying insect and host interaction is essential for environmentally-friendly pest management. Guangcun He and colleagues from Wuhan University identified and characterized a saliva protein BISP of the brown planthopper (BPH). In susceptible varieties, BISP targets OsRLCK185 and inhibits the basic defense. In varieties carrying the brown planthopper resistance gene Bph14, BPH14 directly binds to BISP and activates the host immune response but inhibits rice growth. BISP-BPH14 binds to the autophagic cargo receptor OsNBR1 and results in the degradation of BISP through the autophagic pathway, downregulating rice resistance against BPH and restoring the plant growth. This study illustrated the first insect salivary protein perceived by plant immune receptor, and revealed the molecular mechanism underlying the balance of immunity and growth in host by perceiving and regulating the protein level of insect effectors, which provides new ideas for developing high-yield insect resistant rice varieties.

Clubroot, Plasmodiophora brassicae (Pb) caused devastating disease, results in severe yield losses on cruciferous crops worldwide. Recently, Yu-hang Chen, Jian-Min Zhou and their colleagues from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences reported the isolation and characterization of WeiTsing (WTS), a broad-spectrum clubroot resistance gene from Arabidopsis. WTS in Arabidopsisis was transcriptionally activated in the pericycle upon Pb infection to prevent pathogen colonization in the stele. WTS encodes a small protein that is localized in the endoplasmic reticulum (ER). The cryo-EM structure analysis has revealed a pentameric architecture of WeiTsing with a central pore, which was previously unknown. Electrophysiological analysis has demonstrated that WeiTsing functions as a calcium-permeable cation-selective channel. The Pb-mediated activation of the WTS channels induces immune responses, including cell death. Brassica napus plants carrying the WTS transgene have exhibited robust resistance to Pb. These findings have identified a novel ion channel similar to resistosomes, which triggers immune signaling in the pericycle. This discovery provides a valuable tool for the development of elite crop varieties.

Saline-alkali stress is one of the main adverse environmental factors limiting agricultural production and crop yield. In recent years, great progress has been made in the dissection of the molecular mechanisms of plant’s responses to salt stress, but little is known concerning those for alkaline stress. Lack of the knowledge on alkaline tolerance has severely impeded the effort to improve saline and alkaline stress tolerance of crops through molecular designing and breeding. Recently, Professor Qi Xie at the Institute of Genetics and Developmental Biology of Chinese Academy of Sciences, teamed with Dr. Feifei Yu at China Agricultural University and Dr. Yidan Ouyang at Huazhong Agricultural University, made a breakthrough discovery towards the understanding of the molecular regulation of alkaline tolerance. They detected a major gene AT1, which negatively regulates alkaline tolerance, through sorghum genome-wide association study. The knockout of AT1 and its homologous genes increased the tolerance of sorghum, rice, millet and maize to alkali and increased the yield. AT1 encodes an atypical G protein γ subunit, which alters the cellular distribution of H₂O₂ via regulating the phosphorylation level of the aquaporins PIP2;1 to alleviate the alkali-induced oxidative stress in cells. This work reveals a new mechanism in the adaptation of crops to alkaline stress, which is of great significance to crop breeding for alkaline resistance.

Since the 1960s, the utilization of semi-dwarfing genes Rht-B1b and Rht-D1b has significantly improved the lodging resistance and harvest index of wheat (Triticum aestivum), leading to a doubling of global wheat production and triggering the “Green Revolution” in agriculture. Rht-B1b and Rht-D1b encode plant growth-inhibiting factors, DELLA proteins, which are negative regulatory factors in the gibberellin (GA) signaling pathway. Accumulation of DELLA proteins not only inhibits cell division and elongation, leading to a dwarf phenotype, but also suppresses photosynthesis and nitrogen use efficiency, resulting in semi-dwarf varieties requiring higher fertilizer inputs to achieve high yields. Addressing the challenge of “reducing fertilizer inputs while increasing efficiency” is a crucial issue for achieving green and low-carbon agriculture. Recently, Zhongfu Ni and his colleagues from China Agricultural University identified a novel “semi-dwarfing” regulatory module with potential breeding applications and demonstrated that reducing brassinosteroid (BR) signaling could enhance grain yield of wheat “Green Revolution” varieties (GRVs). They isolated and characterized a major QTL responsible for plant height and 1000-grain weight in wheat. Positional cloning and functional analysis revealed that this QTL was associated with a ~500 kb fragment deletion in the Heng597 genome, designated as r-e-z, which contains Rht-B1 and ZnF-B (encoding a RING E3 ligase). ZnF-B was found to positively regulate BR signaling by triggering the degradation of BR signaling repressor BRI1 Kinase Inhibitor (TaBKI1). Further experiments showed that deletion of ZnF-B not only caused the semi-dwarf phenotypes in the absence of Rht-B1b and Rht-D1b alleles, but also enhanced grain yield at low nitrogen fertilization levels. Thus, manipulation of GA and BR signaling provides a new breeding strategy to improve grain yield and nitrogen use efficiency of wheat GRVs without affecting beneficial semi-dwarfism, which will drive toward a new “Green Revolution” in wheat.

Wheat stripe rust, also known as yellow rust, is a disease caused by the fungus Puccinia striiformis f. sp. tritici (Pst) that can devastate wheat crops across the world. The most effective way to control rust diseases is by planting and breeding durable resistant wheat cultivars. The caveat of R gene-dependent disease resistance is the frequent loss of effectiveness due to pathogen mutations that allow evasion of detection by immune receptors. However, disruption of host baseline susceptibility by inactivating S genes could be adopted for broad-spectrum and durable disease resistance. A recent study finished by the research team at Northwest A&F University significantly advanced our understanding how wheat plants can be protected by a S gene and provided tools in the fight against a major disease. Upon infection, the fungus induces a receptor-like cytoplasmic kinase, TaPsIPK1, specifically interacting with the effector, PsSpg1, that promotes parasitism via enhancing kinase activity and nuclear entry of TaPsIPK1. TaPsIPK1 phosphorylates the transcription factor TaCBF1d for gene regulation. Phosphorylation of TaCBF1d switches its transcriptional activity on the downstream genes. Hence the enhanced TaCBF1d phosphorylation by TaPsIPK1 and PsSpg1 might reprogram target gene expression to disturb plant defense response and thus facilitate pathogen infection. CRISPR-Cas9 inactivation of TaPsIPK1 in wheat confers broad-spectrum resistance against Pst without impacting important agronomic traits in two-years of field tests. This is first study to reveal a new phosphorylation-transcriptional regulation mechanism triggered by PsSpg1-TaPsIPK1-TaCBF1d in wheat S genes to stripe rust, which provide a new strategy to develop cultivars with durable resistance by genetic modifications in crops.

The apoplast is the frontier area for plants to sense and respond to environmental stresses (including biotic and abiotic stresses). The pH of the apoplast is an important physiological parameter that is tightly regulated. Environmental stress (such as bacterial disease) can cause alkalinization of plant apoplast, but how does apoplast pH coordinate root growth and immune response? Its molecular regulation mechanism is still unclear. Recently, the team of Professor Hongwei Guo from the School of Life Sciences, Southern University of Science and Technology, and the team of Professor Jijie Chai from Tsinghua University-Max Planck Institute of Germany-University of Cologne used the model plant Arabidopsis as research materials, through genetic, cellular, biochemical and structural biology. By means of comprehensive methods, it was found that the small peptide-receptor complex on the cell surface can act as an apoplast pH sensor to sense and respond to the apoplast alkalinization of Arabidopsis root apex meristem cells induced by pattern triggered immunity (PTI). The results of this research have discovered the protein complex and response mechanism of plant root apex meristem apoplast pH sensing, as well as the coordination mechanism between immunity and growth, further understanding the biology reaction process of how plants balance growth and immune response.