Regulation of stomatal aperture by SAUR proteins in Arabidopsis thaliana (2016)

Undergraduate: Bryan Wang

Faculty Advisor: Jason Reed
Department: Biology

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SMALL AUXIN UP RNA (SAUR) genes are the largest class of primary auxin (growth hormone) responsive genes in all land plants, many of which are expressed in actively growing plant tissues. This project focuses on the study of four SAUR genes in the model plant Arabidopsis thaliana. Previous studies have indicated that SAUR63 promotes elongation of growing cells by regulating other proteins at the plasma membrane. Overexpression of the protein in a broader domain, including in guard cells, caused the guard cells to swell, leading to constitutive stomatal opening. To test whether other SAUR genes regulate guard cell function in wild-type plants, we are studying three additional members of the family, SAUR30, SAUR56 and SAUR60, which are expressed preferentially in guard cells. We hypothesize that these SAUR genes regulate guard cell function based on their localization. We found that plants that overexpressed and stabilized SAUR60 or SAUR63 proteins exhibited constitutively open stomata, even during physiological conditions favoring stomatal closure. These results suggest that SAUR proteins regulate guard cell function. This is the first demonstration that certain members of the SAUR protein family can lead to open stomata. Similar experiments for SAUR30 and SAUR56 are in progress. We are currently knocking-out these genes to test if they are required to open stomata. This knowledge allows for improvements in physiological traits affecting photosynthesis and drought resistance.