SAUR63 stimulates cell growth at the plasma membrane

• Published in: PLoS genetics 2022-09, Vol.18 (9), p.e1010375-e1010375
• Main Authors: Nagpal, Punita, Reeves, Paul H, Wong, Jeh Haur, Armengot, Laia, Chae, Keun, Rieveschl, Nathaniel B, Trinidad, Brendan, Davidsdottir, Vala, Jain, Prateek, Gray, William M, Jaillais, Yvon, Reed, Jason W
• Format: Article
• Language: English
• Subjects: Adenosine triphosphatase; Amino acids; Analysis; Apoplast; Arabidopsis thaliana; Biochemistry, Molecular Biology; Biology and Life Sciences; Botanics; Cell division; Cell growth; Cell membranes; Cell size; Fusion protein; Genetic aspects; H+-transporting ATPase; Hydrogen; Identification and classification; Kinases; Life Sciences; Lipid composition; Localization; Mutation; Phosphatase; Phosphatases; Plasma; Proteins; Research and Analysis Methods; Sucrose; Vegetal Biology
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1010375

In plants, regulated cell expansion determines organ size and shape. Several members of the family of redundantly acting Small Auxin Up RNA (SAUR) proteins can stimulate plasma membrane (PM) H.sup.+ -ATPase proton pumping activity by inhibiting PM-associated PP2C.D phosphatases, thereby increasing the PM electrochemical potential, acidifying the apoplast, and stimulating cell expansion. Similarly, Arabidopsis thaliana SAUR63 was able to increase growth of various organs, antagonize PP2C.D5 phosphatase, and increase H.sup.+ -ATPase activity. Using a gain-of-function approach to bypass genetic redundancy, we dissected structural requirements for SAUR63 growth-promoting activity. The divergent N-terminal domain of SAUR63 has a predicted basic amphipathic [alpha]-helix and was able to drive partial PM association. Deletion of the N-terminal domain decreased PM association of a SAUR63 fusion protein, as well as decreasing protein level and eliminating growth-promoting activity. Conversely, forced PM association restored ability to promote H.sup.+ -ATPase activity and cell expansion, indicating that SAUR63 is active when PM-associated. Lipid binding assays and perturbations of PM lipid composition indicate that the N-terminal domain can interact with PM anionic lipids. Mutations in the conserved SAUR domain also reduced PM association in root cells. Thus, both the N-terminal domain and the SAUR domain may cooperatively mediate the SAUR63 PM association required to promote growth.