Control of plant exocyst function by protein phosphorylation in root hairs and pollen tubes - regulation of tip growth through AGC1 kinases and exocyst phosphoregulation

• Applicant: Professor Dr. Claus Schwechheimer
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 391059800

• Final Report Year: 2023

Final Report Abstract

Plant roots generate root hairs through polar growth from root epidermis cells for better soil penetration and optimal nutrient uptake. The constant contacts between the growing root hair and soil particles during this process require constant growth adjustments of the root hair, which must be perceived at the cellular level and implemented in the form of changes in the growth direction. Here, AGC1.6 and AGC1.7, two functionally redundant protein kinases, specifically expressed in root hair-producing cells, of the AGC1 protein family from the plant model organism Arabidopsis thaliana were characterized. We could show that these proteins localize just below the root hair tip during root hair growth and localize to the contact site in response to touch and prior to the subsequent change in growth direction. Protein kinase mutants displayed increased elongation growth in hard media, which we categorize as uncontrolled growth. With the help of light-controlled optogenetic protein kinase variants, we revealed that the protein is directly involved in the regulation of growth changes. Root hair growth requires constant transport of membrane components via the cellular exocytosis pathway. In collaboration with Viktor Zarsky's laboratory, we showed that the regulation of the exocytosis protein EXO70C2 by phosphorylation via AGC1 kinases represents a possible mechanism by which the protein kinases interfere with cellular growth. The specific expression of both protein kinases in root hair cells was also used to validate data from a comprehensive Arabidopsis thaliana study examining the distribution of all (detectable) Arabidopsis proteins in 30 tissues.

Publications

• Mass-spectrometry-based draft of the Arabidopsis proteome. Nature, 579(7799), 409-414.
  Mergner, Julia; Frejno, Martin; List, Markus; Papacek, Michael; Chen, Xia; Chaudhary, Ajeet; Samaras, Patroklos; Richter, Sandra; Shikata, Hiromasa; Messerer, Maxim; Lang, Daniel; Altmann, Stefan; Cyprys, Philipp; Zolg, Daniel P.; Mathieson, Toby; Bantscheff, Marcus; Hazarika, Rashmi R.; Schmidt, Tobias; Dawid, Corinna ... & Kuster, Bernhard
  
• Proteomic and transcriptomic profiling of aerial organ development in Arabidopsis. Scientific Data, 7(1).
  Mergner, Julia; Frejno, Martin; Messerer, Maxim; Lang, Daniel; Samaras, Patroklos; Wilhelm, Mathias; Mayer, Klaus F. X.; Schwechheimer, Claus & Kuster, Bernhard
  
• Auxin does not inhibit endocytosis of PIN1 and PIN2 auxin efflux carriers. Plant Physiology, 186(2), 808-811.
  Schwechheimer, Claus; Yalovsky, Shaul & Žárský, Viktor
  
• Auxin Transporters—A Biochemical View. Cold Spring Harbor Perspectives in Biology, 14(2), a039875.
  Hammes, Ulrich Z.; Murphy, Angus S. & Schwechheimer, Claus
  
• Regulation of Exocyst Function in Pollen Tube Growth by Phosphorylation of Exocyst Subunit EXO70C2. Frontiers in Plant Science, 11.
  Saccomanno, Antonietta; Potocký, Martin; Pejchar, Přemysl; Hála, Michal; Shikata, Hiromasa; Schwechheimer, Claus & Žárský, Viktor
  
• Editorial overview: Cell biology and cell signalling. Current Opinion in Plant Biology, 70, 102312.
  Sprunck, Stefanie; Schwechheimer, Claus & Morita, Miyo T.
  
• Phosphorylation control of PIN auxin transporters. Current Opinion in Plant Biology, 65, 102146.
  Bassukas, A.E. Lanassa; Xiao, Yao & Schwechheimer, Claus
  
• Monitoring single root hairs using a micro-chambered hydroponics system MiCHy reveals a new mode of action of the aminosteroid U73122. Cold Spring Harbor Laboratory.
  Shikata, Hiromasa; Sato, Yoshikatsu & Schwechheimer, Claus