Abstract

A genomic sequence corresponding to a putative actin-depolymerizing factor (ADF) was isolated from a wheat (Lophopyrum elongatum) genomic library. The genomic clone, designated ESI28-G-5, codes for the ESI28 gene (early salt-stress induced). The 5$\sp\prime$-upstream sequence contains a putative TATA box and abscisic acid (ABA) response element (ABRE). The genomic clone contains a long open reading frame (ORF) which encodes a polypeptide of 143 amino acids with a predicted molecular mass of 15.95 kDa. The protein has two conserved domains identified as actin and phosphatidylinositol 4,5-biphosphate (PIP2) binding sites which are commonly found in members of the cofilin family. A search of DNA sequence databases indicated that the ESI28 sequence had the highest degree of sequence similarity to the Triticum aestivum low temperature regulated gene (Wcor719) which encodes an actin-binding protein (ABP). The induction of ESI28 by salt, the presence of ABRE in its promoter region, and the significant homology with ABP from different organisms suggest that this gene might be involved in reorganizing the cytoskeleton during water deficit stress. It may also serve as an essential factor in the salt stress signal transduction pathway that is regulated by ABA.