ABSTRACT
Cloning of drought responsive genes and validating their function are essential to crop improvement. In the present study, a drought responsive AP2/ERF family transcription factor was isolated from drought-tolerant Oryza sativa L. cv N-22 (AP2/ERF-‘N-22’). Embryogenic calli produced in vitro from dehusked mature seeds of rice were bombarded with a gene construct containing AP2/ERF-N22, driven under inducible promoter RD29A from Arabidopsis using the Biolistic method. The bombarded calli were selected on hygromycin-containing selection medium. Molecular analysis of regenerated plants confirmed the integration and enhanced expression of the gene under water deficit stress (WDS). Transgenics showed 1.4 fold more expression as compared to wild-type (WT) under control condition and up to 2 fold more expression of AP2/ERF-‘N-22’ under water deficit stress as compared to WT. Molecular analysis of regenerated plants confirmed the integration and enhanced expression of the gene under water deficit stress. The transformation efficiency was found to be nil, 0.97% and 3.11% for overstored seeds ≥ a year, ≥a year and fresh seeds respectively. Transgenics showed 1.4 fold more expression under control condition and up to 2 fold more expression under WDS as compared to wild-type (WT). About 90% of the plants reached maturity and showed no negative phenotypic effects or aberrations as observed earlier under a constitutive promoter from that of the WT. Physiobiochemical analysis of transgenics showed enhanced drought tolerance.
ABSTRACT
Understanding the biochemical and molecular basis of drought mechanism in rice is important as drought is one of the major causes affecting rice crop adversely. A 1017 bp gene sequence encoding AP2/ERF family TF was isolated from Oryza sativa sp. Indica cv N22 encoding a protein of 338 amino acid residues, with a molecular weight of 36.58 kDa, and no intron in the ORF. The gene was named as AP2/ERF-N22(2) different from the drought responsive gene AP2/ERF-N22 that we reported earlier. AP2/ERF-N22(2) has entirely different characteristics from that of AP2/ERF-N22. It has a single AP2 domain of 55 amino acid residues and a cluster of acidic amino acid residues at the C-terminal region, which could function as a trans-activation domain. Presence of NLS indicates that it is a nuclear localized transcription factor encoding gene. It falls in group VI L, sharing characteristic similarities. Arabidopsis members of group VI L have been shown to be involved in response to cytokinin under drought stress.