Molecular cloning and expression of drought-induced protein 3 (DIP3) encoding a class III chitinase in upland rice

A drought-induced gene, DIP3, encoding a chitinase III protein was isolated from the roots of upland rice by reverse transcription-polymerase chain reaction (RT-PCR). Sequence analysis demonstrated that the cDNA and deduced protein showed high identity to Oryza sativa class III chitinase. The deduced protein contained a signal peptide sequence in the N-terminal region of 21aa and a conserved glycosyl hydrolase (GH) 18 domain. The secondary and 3D structures were analyzed and showed that it contained α-helix, β-sheets, extended strand and random coil structures and that it was approximately spheroidal. Real-time quantitative PCR analysis revealed that expression levels accumulated rapidly under different forms of abiotic stress (drought, salt and low temperature), peaked at different times and then decreased. These results implied that as a member of class III chitinases, DIP3 may function as a stress-induced protein involved in the regulation of plant stress response.