Expression analysis of bZIP transcription factor encoding genes in response to water deficit stress in rice.

In plants, basic region/leucine zipper motif (bZIP) transcription factors regulate several developmental processes and activate genes in response to biotic and abiotic stresses. Role of stress responsive bZIP transcription factors was studied in paddy in relation to different stages of development and water deficit stress (WDS) in a drought tolerant cultivar N22 and susceptible IR 64. Further, relative water content (RWC), membrane stability index (MSI) and abscisic acid (ABA) content were measured as indices of WDS at different stages of development and levels of stress. Expression of stress responsive bZIP transcription factors was directly correlated to developmental stage and WDS and indirectly to RWC, MSI and ABA content.

Cloning and characterization of a water deficit stress responsive transcription factor gene from Oryza sativa L.

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.

Cloning and characterization of a gene encoding novel zinc finger protein transcription factor induced under water deficit stress from rice (Oryza sativa) cv. N-22.

A gene OsZnI encoding Cys3/His1-type zinc finger protein was isolated from the water stress-induced cDNA library of rice (Oryza sativa) cv. N-22, an early maturing, deep-rooted, drought-tolerant genotype adapted to upland conditions. The in-silico analysis revealed an insert of 800 bp with an ORF of 663 nucleotides, encoding 221 amino acids. OsZnI had three distinct features — nuclear localization signal (NLS) present in Arg152-Arg168, Zn finger domain between 185-193 amino acids and 12 amino acids conserved domain in 71-82 amino acids homologous to LEA motif, and belonged to C-type family of Zn finger protein. OsZnI showed induced expression under water deficit stress.