Cloning of a dhn Gene from Pinus massoniana and Characterization of the Responses to Drought Stress in Arabidopsis thaliana

Abstract

Dehydrins (DHNs) play important roles as hydrophilic proteins in plant response to abiotic stress conditions such as salinity, cold, heavy metals, and drought. To determine the genes involved in drought stress in Pinus massoniana, we cloned a DHN gene using degenerate primers and a RACE strategy, and evaluated the gene function using transgenic Arabidopsis thaliana plants overexpressing the DHN gene of P. massoniana under drought stress. The designated full-length Pmdhn (1,232 bp) was found to include a 199 bp 5′and a 316 bp 3'-terminal untranslated region (UTR), and a 717 bp open reading frame (ORF). Pmdhn was characterized as a mature 238 amino acid protein, containing a Ser-rich domain and three conserved replications of the characterized Lys-rich domain. The qRT-PCR analysis revealed that the Pmdhn expression levels in roots and stems were higher than in leaves, and the gene was involved in a broad spectrum of physiological processes under drought stress. No differences in the phenotypes and root lengths between the wild-type and transgenic A. thaliana were observed under normal conditions. Nevertheless, the transgenic A. thaliana lines had longer roots than in the wild-type lines under drought stress. RT-PCR and GFP analysis revealed that Pmdhn can be transcribed stably. Furthermore, the Pmdhn-overexpressing plants showed lower levels of malondialdehyde (MDA), higher water and proline contents under drought stress. These findings indicate that Pmdhn likely plays a role in the process of drought stress.