Characterization of a Subfamily of Small Auxin-Up RNA (SAUR) Genes in Arabidopsis thaliana (2010)

Undergraduate: Cameron Isaacs

Faculty Advisor: Jason Reed
Department: Biology

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The hormone auxin plays an important role in regulating gene expression during plant growth and development, and plants often rely on complex transport systems to shuttle auxin into growing or developing tissues. Among rapidly-induced auxin-responsive gene families in plants, the functions of two (Aux/IAAs and GH3s) are understood. My research focuses on a third auxin-induced group, the Small Auxin-Up RNA (SAUR) genes. To examine the function of one subfamily of SAUR genes in the model plant Arabidopsis thaliana, I characterized SAUR gain- and loss-of-function phenotypes in transgenic plants and analyzed localization of SAUR63 fusion proteins. Putative gain-of-function SAUR lines had increased auxin transport and exhibited several auxin-associated phenotypes, including elongated and kinked hypocotyls, twisted inflorescences, and elongated petals and stamen filaments. Loss-of-function SAUR lines had shortened (and straight) hypocotyls, petals, and stamen filaments. A SAUR63:GFP fusion protein was present in the plasma membrane of epidermis cells in the upper hypocotyl and cotyledons. My results suggest that SAUR proteins help regulate intracellular auxin concentrations by promoting auxin transport throughout rapidly-growing tissues. In addition to describing a novel class of proteins, these results expand our understanding of how auxin self-regulates to produce coordinated and synchronized developmental responses.