Isolation and characterization of a novel potato Auxin/Indole-3-Acetic Acid family member (StIAA2) that is involved in petiole hyponasty and shoot morphogenesis.

Auxin/indole-3-acetid acid (Aux/IAA) proteins are short-lived transcriptional regulators that mediate their response through interaction with auxin response factors (ARF). Although 29 Aux/IAA proteins have been identified in Arabidopsis thaliana, their individual functions are still poorly understood and are largely defined by observed growth defects in gain-of-function mutant alleles. Here we present the isolation and characterization of a novel Aux/IAA protein in potato (Solanum tuberosum) that is named StIAA2. Down regulation of StIAA2 results in distinctive phenotypes that include, increased plant height, petiole hyponasty and extreme curvature of growing leaf primordia in the shoot apex. Gene expression analysis of transgenic plants with reduced StIAA2 transcript levels resulted in the identification of a number of genes with altered expression profiles including another member of the Aux/IAA gene family (StIAA). The phenotypes that were observed in the StIAA2 suppression clones can be associated with both common as well as unique functional roles among Aux/IAA family members indicating the importance of analyzing Aux/IAA expression in different plant species.