[Isolation of OsFAD2, OsFAD6 and FAD family members response to abiotic stresses in Oryza sativa L.].

Unsaturated fatty acids are synthesized by fatty acid desaturase in plant, which play an important role in plant development and defense to abiotic stresses. The key enzymes for the conversion of oleic into linoleic acid were isolated from rice (Oryza sativa L.) and were designated OsFAD2 and OsFAD6, respectively. The open reading frame (ORF) of OsFAD2 was 1 167 bp in length, which encoded a 388 amino acids sequence with the isoelectric point of 8.17 and molecular mass of 52.24 kDa, the OsFAD2 protein contained a C-terminal ER retrieval motif. The ORF of OsFAD6 was 1 365 bp in length and the predicted OsFAD6 protein has 454 amino acids with an estimated molecular mass of 44.35 kDa and an isoelectric point of 9.24, the predicted OsFAD6 protein possessed a putative N-terminal plastidial signal peptide. Both of them had three his-boxes, which were peculiar to membrane integrated fatty acid desaturase by Clustal X analysis. RT-PCR analysis showed that both genes were expressed in all tissues rice seedlings, with the maximum transcript accumulation in leaves. Among FAD family members of Oryza sativa L., the mRNA abundance of OsFAD2 and OsFAD6 in leaves did not change under cold stress; however, the mRNA abundance of OsFAD7 and OsFAD8 increased in the same condition. It was also found that the expression of FAD family members had diurnal rhythm phenomena. Based on the results of this study, it suggested that diurnal rhythm expression of OsFAD6 and OsFAD7 was related to the change of NADPH abundance.