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.The data are provided as an .xlsx file with multiple tabs, and can be opened with Microsoft Excel or other software. Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: MCB-16155571. Description of methods used for collection/generation of data: A link to the publication that incorporates this data will be provided here upon acceptance. That publication describes methods for each experiment. 2. Methods for processing the data: The submitted data for most tabs are raw measurements and are not processed. Data for Figures S2 (calculated cell dimensions), 2I (calculated HPTS fluorescence ratios), and S5E (calculated HPTS fluorescence ratios) have already been processed, as indicated in the corresponding tabs. 3. Instrument- or software-specific information needed to interpret the data: A plugin for ImageJ was used to analyze HPTS fluorescence images in Figures 2I and S5E, as described in: Barbez E, Dunser K, Gaidora A, Lendl T, Busch W. Auxin steers root cell expansion via apoplastic pH regulation in Arabidopsis thaliana. Proceedings of the National Academy of Sciences of the United States of America. 2017;114(24):E4884-E4893. 4. Standards and calibration information, if appropriate: For length and area measurement data that are in raw format from ImageJ measurements of scanned images, the appropriate conversion factor to convert to standard units is listed with the data. 5. Environmental/experimental conditions: Conditions for each experiment are listed within the corresponding data tab. See also the Methods section of the associated publication