J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (9): 2122-2137.DOI: 10.1111/jipb.13536

• Functional Omics and Systems Biology • Previous Articles     Next Articles

Cell type-specific proteomics uncovers a RAF15-SnRK2.6/OST1 kinase cascade in guard cells

Hongliang Wang1†, Yubei Wang1,2†, Tian Sang3†, Zhen Lin3, Rongxia Li4, Weiwei Ren5, Xin Shen6, Bing Zhao7, Xiao Wang7, Xuebin Zhang7, Shaoqun Zhou8, Shaojun Dai5, Honghong Hu6, Chun‐Peng Song7 and Pengcheng Wang3*   

  1. 1. Shanghai Center for Plant Stress Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China;
    3. Institute of Advanced Biotechnology and School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China;
    4. Shanghai Bioprofile Technology Company Ltd, Shanghai 200241, China;
    5. Center of Plant Germplasm Resources, College of Life Sciences, Shanghai Normal University, Shanghai 200234, China;
    6. National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China;
    7. State Key Laboratory of Crop Stress Adaptation and Improvement, College of Life Sciences, College of Agriculture, Academy for Advanced Interdisciplinary Studies, Henan University, Kaifeng 475004, China;
    8. Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Key Laboratory of Synthetic Biology, Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China
    These authors contributed equally to this article.
    *Correspondence: Pengcheng Wang (wangpc@sustech.edu.cn)
  • Received:2023-05-09 Accepted:2023-05-23 Online:2023-05-25 Published:2023-09-01

Abstract: Multicellular organisms such as plants contain various cell types with specialized functions. Analyzing the characteristics of each cell type reveals specific cell functions and enhances our understanding of organization and function at the organismal level. Guard cells (GCs) are specialized epidermal cells that regulate the movement of the stomata and gaseous exchange, and provide a model genetic system for analyzing cell fate, signaling, and function. Several proteomics analyses of GC are available, but these are limited in depth. Here we used enzymatic isolation and flow cytometry to enrich GC and mesophyll cell protoplasts and perform in-depth proteomics in these two major cell types in Arabidopsis leaves. We identified approximately 3,000 proteins not previously found in the GC proteome and more than 600 proteins that may be specific to GC. The depth of our proteomics enabled us to uncover a guard cell-specific kinase cascade whereby Raf15 and Snf1-related kinase2.6 (SnRK2.6)/OST1(open stomata 1) mediate abscisic acid (ABA)-induced stomatal closure. RAF15 directly phosphorylated SnRK2.6/OST1 at the conserved Ser175 residue in its activation loop and was sufficient to reactivate the inactive form of SnRK2.6/OST1. ABA-triggered SnRK2.6/OST1 activation and stomatal closure was impaired in raf15 mutants. We also showed enrichment of enzymes and flavone metabolism in GC, and consistent, dramatic accumulation of flavone metabolites. Our study answers the long-standing question of how ABA activates SnRK2.6/OST1 in GCs and represents a resource potentially providing further insights into the molecular basis of GC and mesophyll cell development, metabolism, structure, and function.

Key words: abscisic acid, guard cell, metabolomics, phosphorylation, proteomics, signaling

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