Genome-wide analysis of Aux/IAA genes in Vitis vinifera: cloning and expression profiling of a grape Aux/IAA gene in response to phytohormone and abiotic stresses

Auxin is one of the most important phytohormones involved in plant growth and development. Here, we identified a total of 26 Aux/IAA genes displaying high sequence identity within the conserved domains I, II, III, and IV by screening the grapevine genome proteome 12× database. The Vitis vinifera Aux/IAA proteins can be classified into two groups (A and B) on the basis of their phylogenetic relationships. A search for cis-regulatory elements in the promoter sequences of VvAux/IAA genes revealed that the majority of these proteins may be regulated by light, phytohormones, and abiotic stresses. We also report the isolation and expression analysis of the cDNA of VvAux/IAA4, the most highly expressed VvAux/IAA gene from V. vinifera cv. Sultanine, according to ESTs in the NCBI database. The VvAux/IAA4 gene contains a full-length open reading frame of 1,080 bp, and its predicted amino acid sequence is highly similar to those of Aux/IAA proteins from other plants, including the presence of an AuxIAA/ARF dimerization motif in the C-terminal region. The expression of VvAux/IAA4 was found to be elevated during berry development, and slowly decrease from the initiation of ripening to the overripening stage. VvAux/IAA4 was highly expressed in young leaves and roots, and expressed at low levels in pollen and tendrils. Finally, the expression of VvAux/IAA4 was rapidly induced in response to NAA treatment, but was decreased by salt, drought, and SA treatments. Our results provide evidence of crosstalk between phytohormone and abiotic stresses, and support a role for auxin in stress responses.