Arabidopsis SAUR63 seedling phenotypes and fluorescent fusion protein localization

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+-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+-ATPase activity.  This
dataset includes i) measurements of seedling growth in plants with altered
activity of SAUR63 and PP2C.D5; ii) data from fluorescent images to
measure extracellular pH; iii) analyses of subcellular localization of
SAUR63:YFP fusion protein variants in roots; and iv) SAUR63:YFP
localization after transient expression in Nicotiana benthamiana leaves
with perturbed plasma membrane lipid composition.  These data
underlie figures presented in the linked manuscript.  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 α-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+-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.  Data is licensed by the
authors for use and distribution subject to citation of the original
source in accordance with the Creative Commons Attribution (CC BY)
license.