Genome-wide identification and characterization of Aux/IAA gene family in grape and functional identification of VaIAA3 in response to cold stress

The Aux/IAA gene is a key gene that regulates auxin signal transduction in plants. Although IAA genes have been characterized in various plant species, the role of the IAA gene in grape cold resistance is unclear. In order to further explore the members of Aux/IAA gene family in grape and their functions, in this study, based on the genomic data of ‘Pinot Noir’ (Vitis vinefera cv. ‘Pinot Noir’) and Shanputao (Vitis amurensis), 25 VvIAA genes and 18 VaIAA genes were identified. The VaIAA genes exhibited different expression patterns under diferent temperature periods by qPCR. VaIAA3 was selected as a candidate gene for further functional analysis because of its high expression level under low temperature stress. The subcellular localization showed that VaIAA3 was localized in the nucleus. Additionally, under 4°C treatment at 24 h, the relative expression level of VaIAA3 and antioxidant enzyme activity of the three transgenic lines (OE-1, OE-2, OE-3) were significantly increased, while the contents of relative electrolytic conductivity (REC), malondialdehyde (MDA) and hydrogen peroxide (H2O2) were lower under cold stress. Taken together, these results provide some possibilities to study the identification and function of Aux/IAA gene families in different grape varieties. Importantly, heterologous over-expression of VaIAA3 can enhance resistance of Arabidopsis thaliana under cold stress, which provides a theoretical basis for further use of IAA3 gene to improve grape agronomic traits.