Ion channels regulate nitrogen–potassium balance

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Liu et al. reveal that anion channel SLAH3 forms complexes with potassium channels GORK and SKOR to modulate membrane potential via coordinating nitrogen–potassium balance.

By Beibei Liu and Kai He

Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China

Background: The nitrogen (N)–potassium (K) balance not only profoundly affects plant growth but also serves as an essential signal to regulate plant–environment interactions. However, the detailed molecular mechanisms that maintain the N–K balance are largely unknown.

Question: How does the nitrate efflux channel SLAH3 regulate the N–K balance in plants?

Findings: The anion channel SLAH3 mediates NO3− efflux under high K+ conditions. The accelerated depolarization next causes the opening of the K+ channels GORK and SKOR to mediate K+ efflux. The channel–channel interaction may also be important for manipulating K+ channel activities. We found that the N–K balance is regulated by N and K channels, with both the membrane potential and the interactions between these membrane proteins modulating this regulation.

Next steps: As anion and cation channels function coordinately to regulate the N–K balance, the corresponding genes could be used to construct novel crop variants that can withstand diverse N–K environments through molecular breeding.

Beibei Liu, Changxin Feng, Xianming Fang, Zhen Ma, Chengbin Xiao, Shuaishuai Zhang, Zhenzhen Liu, Doudou Sun, Hongyong Shi, Xiaoqin Ding, Chenyang, Qiu, Jia Li, Sheng Luan, Legong Li, and Kai He. (2023). The anion channel SLAH3 interacts with potassium channels to regulate nitrogen–potassium homeostasis and the membrane potential in Arabidopsis. https://doi.org/10.1093/plcell/koad014

Elucidating elicitin recognition

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Chen et al. explore the recognition of Phytophthora effectors in Nicotiana benthamiana and the conservation of these responses in the Solanaceae

Background: Plant pathogens employ effectors as weapons to invade and colonize plant tissue. To counteract these effectors, plants have developed surveillance systems that are activated by microbial effectors thereby warning the plant about pathogen attack and triggering defense responses. Phytophthora species are notorious plant pathogens affecting numerous crops, trees, and ornamentals. They secrete a variety of effectors including elicitins, effectors that are unique for Phytophthora and can recruit sterols from host plants for their own benefit. Elicitins also induce cell death in Nicotiana species and some wild Solanum species pointing to functional surveillance systems for elicitins. Elicitin recognition in Solanum microdontum is mediated by a membrane-localized receptor named ELR (ELicitin Response), and heterologous expression of the ELR gene in cultivated potato (Solanum tuberosum) increases resistance to Phytophthora infestans.

Questions: How are elicitins recognized in Nicotiana species? Are the mechanisms underlying elicitin recognition conserved in different plant species?

Findings: We identified a receptor-like protein in Nicotiana benthamiana that we named REL (for Responsive to ELicitins). REL has an extracellular leucine-rich repeat domain that mediates Phytophthora resistance by recognizing and binding different elicitins. Domain deletion and site-directed mutagenesis revealed that a specific domain in REL is crucial for elicitin recognition. In addition, sequence polymorphism in this domain underpins the genetic diversity of REL homologs in various Nicotiana species in elicitin binding and recognition. REL is phylogenetically distant from the S. microdontum elicitin response protein ELR and differs from ELR in its ability to bind and recognize elicitins.

Next steps: Future research will further unravel the mechanisms underlying elicitin recognition by REL and investigate the capability of REL and modified RELs to confer resistance to a broad range of Phytophthora species in various plant species. The long-term goal is to use these elicitin receptors to engineer crops with durable Phytophthora resistance.

Reference:

Zhaodan Chen, Fan Liu, Mengzhu Zeng, Lei Wang, Hanmei Liu, Yujing Sun,  Lan Wang, Zhichao Zhang, Zhiyuan Chen, Yuanpeng Xu, Mingmei Zhang,  Yeqiang Xia, Wenwu Ye, Suomeng Dong, Francine Govers, Yan Wang,  Yuanchao Wang (2023) Convergent evolution of immune receptors underpins distinct elicitin recognition in closely related Solanaceous plants. https://doi.org/10.1093/plcell/koad002

 

Vacuole formation in the female gametophyte

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Hu and Yu et al. demonstrate that BIN2-VLG module regulates vacuole formation in female gametophyte.

By Li-Qin Hu, Shi-Xia Yu, and Wen-Hui Lin

Background: In Arabidopsis, the development of the female gametophyte (FG) within the ovule is essential for plant reproduction and seed yield. Formation of the large vacuole within the FG is required for FG expansion, nuclear polar localization, and cell fate determination, which is critical for successful double fertilization. Generally, the large vacuole is visible after the first nuclear division during FG development. VACUOLELESS GAMETOPHYTES (VLG) regulates FG development by facilitating vesicular fusion to form large vacuole, but how VLG is regulated in this process remains unclear.

Question: How does the spatiotemporal formation of the large vacuole influence Arabidopsis FG development? How is VLG function regulated during FG development?

Findings: BRASSINOSTEROID INSENSITIVE2 (BIN2) is expressed in the FG and localizes in vesicular-like structures. Increased BIN2 activity (in the gain-of-function mutant bin2-1) enhances VLG stability through preventing its degradation by the 26S proteasome; the increase in VLG promotes large vacuole formation at stage FG1. Decreased BIN2 activity (in the loss-of-function mutant of BIN2 and its homologs bin2-3 bil1 bil2) reduces VLG stability, which decreases vacuole formation at stage FG2. Both conditions impair FG development. Overall, our study revealed that the spatiotemporal formation of large vacuoles regulated by the BIN2-VLG module is required for normal FG development.

bin2-1 triggers vacuole early formation at stage FG1

Next steps: Further studies will elucidate mechanisms by which early formation of the large vacuole disturbs nuclear division and FG development. We speculate that it changes the condition of organelles and micro-environment of the functional megaspore at stage FG1. So, we will further study how the first nuclear division of FG is affected. This work could contribute to understanding how FG development is triggered after the functional megaspore formed.

Reference:

Li-Qin Hu, Shi-Xia Yu, Wan-Yue Xu, Song-Hao Zu, Yu-Tong Jiang, Hao-Tian Shi, Yan-Jie Zhang, Hong-Wei Xue, Ying-Xiang Wang and Wen-Hui Lin. (2023). Spatiotemporal formation of the large vacuole regulated by the BIN2-VLG module is required for female gametophyte development in Arabidopsis. https://doi.org/10.1093/plcell/koad007

F-actin in the synergid cell regulates the secretion of pollen tube attractants like a fishing rod

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Susaki et al. explore the role of the cytoskeleton of synergid cells during sexual reproduction of angiosperms.

By Daichi Susaki, and Daisuke Maruyama

Kihara Institute for Biological Research, Yokohama City University, Japan.

Background: The two synergid cells embedded in the ovule of angiosperms play an important role in the male–female interaction during sexual reproduction by secreting pollen tube attractants (e.g., AtLUREs). The micropylar end of a synergid cell has a filiform apparatus, active communication domain with complex plasma membrane invaginations and thick cell walls that presumably secrete the attractant peptides. Immunostaining studies have shown radial microtubules spreading from the filiform apparatus and filamentous actin (F-actin) distributed longitudinally within the synergids. The characteristic morphology and cytoskeletal orientation of synergid cells are thought to be important for their function, but the details are unclear.

Question: What is the function of the cytoskeleton in synergid cells during sexual reproduction?

Findings: We demonstrated that microtubule destruction compromises the elongation of plasma membrane invaginations in the filiform apparatus. Disruption of F-actin resulted in severe disorganization of synergid cell morphology, causing incomplete filiform apparatus formation and aberrant positioning of the central vacuole. Furthermore, F-actin destruction impaired the secretion of pollen tube attractant peptides and caused female sterility. After pollen tube discharge, the longitudinal F-actin pattern temporarily disappeared in the persistent synergid. Our data suggest that F-actin has a central role in maintaining cell polarity and in mediating male–female communication in the synergid cell.

Next step: The genes that regulate the polar secretion and cell morphology of synergid cells remain to be identified in further studies. Such studies will further our understanding of the mechanisms that underlie pollen tube attraction and polytubey block, the process by which the ovule limits the number of pollen tubes it attracts.

Daichi Susaki, Rie Izumi, Takao Oi, Hidenori Takeuchi, Ji Min Shin Naoya Sugi, Tetsu Kinoshita, Tetsuya Higashiyama, Tomokazu Kawashima and Daisuke Maruyama. (2023). F-actin regulates the polarized secretion of pollen tube attractants in Arabidopsis synergid cells https://doi.org/10.1093/plcell/koac371

 

Peng Li: Plant Physiology First Author

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Peng Li, first author of “Peronophythora litchii RXLR effector PlAvh202 destabilizes a host ethylene biosynthesis enzyme” 

Current Position: PhD candidate at Guangdong Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University

Education: 2015.09–2018.06, Master degree of Agriculture, Henan Institute of Science and Technology

2018.09– , PhD candidate, South China Agricultural University

Non-scientific Interests: Music, Hiking

Brief biography: The interaction between host plants and pathogens became my interest and research subject, since I joined the Guangdong Key Laboratory of Microbial Signals and Disease Control, a dynamic team supervised by professor Zide Jiang of South China Agricultural University. In our study, a RXLR effector PlAvh202 secreted by Peronophythora litchii was used as a molecular probe to explore the mechanism of plant immunity. By Co-IP, LC-MS/MS, GST-Pull down, SLC, and ethylene quantification, we identified a plant target of PlAvh202 and revealed the mechanism that PlAvh202 targets and destabilizes SAMS by 26S proteasome, leading to the suppression of ethylene-mediated pathogen resistance. We firstly found that SAMS could be captured and destabilized by oomycete RXLR effector, which is distinct from previous studies that virus interfered with plant resistance by altering the enzyme activity of SAMS. Our study provides a new potential target for plant resistance breeding.

第一作者：李鹏

目前职位：华南农业大学微生物信号与病害防控重点实验室，博士研究生

教育经历：2015.09–2018.06，河南科技学院硕士研究生

2018.09至今，华南农业大学微生物信号与病害防控重点实验室，博士研究生

兴趣爱好：音乐，徒步旅行

个人简历：自师从姜子德教授并加入华南农业大学微生物信号与疾病防控重点实验室后，我主要从事病原菌与寄主植物互作机制的研究。我们是一个充满活力的团队，并且我对目前的研究有着浓厚的兴趣。本研究利用荔枝霜疫霉分泌的一个RXLR效应蛋白作为探针，探究植物免疫机制。通过免疫共沉淀、液相色谱串联质谱、GST pull-down、萤火素酶互补和乙烯定量等实验，我们鉴定到了PlAvh202在寄主植物中的靶标，并揭示了其作用机制：PlAvh202与植物中的SAMS互作，促进26S蛋白酶体依赖的SAMS降解，最终抑制了乙烯介导的植物抗病能力。与病毒干扰SAMS酶活力机制不同的是，我们首次发现卵菌RXLR效应分子可以靶向SAMS蛋白，并促进其降解。我们的研究为荔枝抗病育种提供了一个新的潜在靶标。

Adventitious root formation in apple

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Mao et al. demonstrate that MdTCP17 inhibits adventitious root primordium formation in apple rootstocks. The Plant Cell (2023).

 Background: Adventitious root (AR) formation is important for vegetative propagation in plants and is critical for plant breeding and propagation, particularly in plants such as apple (Malus domestica). Cytokinin inhibits AR formation, and members of the TCP families participate in various aspects of plant growth.

Question: Why is it difficult for some plants to form ARs? Do TCP-mediated cytokinin responses affect AR primordium formation in apple?

Findings: We found that a low endogenous cytokinin content improved AR formation in apples. We also found a negative correlation between the expression of cytokinin-responsive MdTCP17 and AR formation, while overexpression of MdTCP17 in transgenic apples inhibited AR formation. MdWOX11 promotes AR formation and MdTCP17 interacts with MdWOX11. MdWOX11 directly binds to the promoter of MdLBD29 and positively regulates its expression. Furthermore, MdTCP17 reduced the binding of MdWOX11 to the MdLBD29 promoter, and co-expression of MdTCP17 and MdWOX11 reduced MdLBD29 expression. Our study thus revealed a mechanism by which MdTCP17 and cytokinin inhibit AR primordium formation.

Next steps: Whether other regulatory mechanisms affect AR formation is unclear. For instance, what are the downstream target genes of MdTCP17?

Reference:

Jiangping Mao, Chundong Niu, Ke Li, Li Fan, Zhimin Liu, Shaohuan Li, Doudou Ma, Muhammad Mobeen Tahir, Libo Xing, Caiping Zhao, Juanjuan Ma, Na An, Mingyu Han, Xiaolin Ren, Dong Zhang (2023) Cytokinin-responsive MdTCP17 interacts with MdWOX11 to repress adventitious root primordium formation in apple rootstocks. https://doi.org/10.1093/plcell/koac369

Mazen Alazem: Plant Physiology First Author

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Mazen Alazem, first author of “Viral synergism suppresses R gene-mediated resistance by impairing downstream defense mechanisms in soybean”

Current Position: Research Scientist, Danforth Plant Science Center

Education: PhD in Biotechnology from National Chung-Hsing University, Taiwan.

Non-scientific Interests: Soccer, Table Tennis, Hiking.

Brief bio:

I am a plant virologist who earned my PhD and completed postdoctoral training at Academia Sinica in Taipei, Taiwan. I began working on my published project, ‘Viral Synergism Effect on R-Gene Resistance in Soybean,’ when I moved to Seoul National University in South Korea as a research assistant professor. The project was challenging because the VIGS tool itself (BPMV vector) can break specific R-resistance against compatible viruses (such as SMV). Now that the project is published, I am focusing on my next research project, which addresses viral effects on plasmodesmata structure and biogenesis. Outside of work, I enjoy hiking, playing soccer, table tennis, or any physical activity that takes me away from bench/office work. Ultimately, I believe it’s important to maintain a balance between work, family, and personal life.

Markéta Šámalová: Plant Physiology First Author

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Markéta Šámalová, first author of “Hormone-regulated expansins – expression, localization and cell wall biomechanics in the control of Arabidopsis root growth”

Current Position: Assistant Professor, Department of Experimental Biology, Masaryk University, Brno, Czech Republic

Education: Ph.D. in Plant Physiology

Non-scientific Interests: traveling, swimming, fungal forays

Brief bio:

During my Ph.D. I focused on basic research in Ian Moore`s laboratory at Oxford University at the Department of Plant Sciences. I participated in the development of one of the most sensitive, fast and tightly regulated chemically inducible systems, the pOp6/LhGR system, for model plant species (Arabidopsis, tobacco and rice). As a postdoc, we established a fluorescence toolkit for quantitative and qualitative ratiometric fluorescence imaging assays that have been successfully used in a number of endomembrane trafficking studies. Later, I shifted my interest to fungal research as we tried to develop strategies to combat the major rice pathogen Magnaporthe oryzea. I then switched to medical science at the Pasteur Institute in Paris, where we searched for a putative cure for aspergillosis, a fatal human disease, and identified a potentially suitable candidate gene for immunization therapy.

Finally, I returned to plant science, back to my alma mater, where I recently founded my own Laboratory of Plant Molecular Biology at the Masaryk University in Brno. Combining my expertise from various scientific fields, I focus on multidisciplinary research. Together with physicists, mathematicians and material scientists, we are developing new tools for imaging, probing and quantifying the biomechanical properties of plant cell walls. I also teach molecular and cellular biology of plants and train practical methods used for genetic modification of plants. I would like to apply my acquired knowledge and scientific experience in research and teaching in the Czech Republic to improve the quality of education and life of future generations.

Zhenkun Liao: Plant Physiology First Author

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Zhenkun Liao, first author of “A multifunctional true CCoAOMT enzyme participates in the biosynthesis of polymethoxylated flavones in citrus”

Current Position: Ph.D. student in Zhejiang University

Education: 2015.09-2019.06, Hainan University, Bachelor

2019.09-now, Zhejiang University, Ph.D

Non-scientific Interests: Reading, Traveling

Brief bio:

Since July 2019, I joined the laboratory of Professor Chongde Sun to pursue PhD. During this period, I worked on the molecular mechanisms of citrus polymethoxylated flavones (PMFs) biosynthesis. PMFs are a kind of flavones with abundant bioactivities and specific existence in Citrus spp, but their biosynthesis mechanisms are not fully clarified. In this study, a member of the true CCoAOMT subgroup, CsCCoAOMT1, was identified from Citrus sinensis. Through functional analysis in vitro and verification in vivo, it was found that CsCCoAOMT1 participated in the biosynthesis of different PMF components and promoted the accumulation of PMFs in citrus. Additionally, the catalytic activity of CsCCoAOMT1 on lignin precursors and coumarin was also found. Our study further refines the biosynthesis mechanism of PMFs in citrus and reveals new functions of the true CCoAOMT subgroup in plants.

 

姓名：廖震坤

目前职位：浙江大学，博士研究生

教育经历：

2015.09-2019.06，海南大学，学士

2019.09-至今，浙江大学，博士研究生在读

兴趣爱好：阅读，旅行

个人简介：

本人于2019年加入孙崇德老师课题组直接攻读博士学位，进行柑橘多甲氧基黄酮（PMFs）生物合成分子机制相关研究。PMFs是一类具有高活性且特异性存在于柑橘属植物中的黄酮类化合物，但其生物合成机制尚未完全明确。本研究从冰糖橙（Citrus Sinensis）中鉴定到一个来自true CCoAOMT亚组的成员CsCCoAOMT1，通过体外功能分析和体内植物验证发现了其参与柑橘不同PMF组分生物合成，促进柑橘中PMFs的积累。此外，本研究还发现CsCCoAOMT1对木质素前体和香豆素底物的催化活性。我们的研究进一步完善了柑橘PMFs的生物合成机制，揭示了true CCoAOMT亚组在植物中的新功能。