Isolation and expression of CsFAD7 and CsFAD8, two genes encoding ω-3 fatty acid desaturase from Camellia sinensis

The plastidial omega-3 fatty acid desaturase catalyses the production of trienoic fatty acids (TAs) in plant chloroplasts and plays an important role in plant responses to environmental stress. In this study, the full-length cDNAs encoding two plastidial omega-3 desaturases, designated CsFAD7 and CsFAD8 (GenBank Accession No. JX943516 and KC847167, respectively), were isolated from the tea plant (Camellia sinensis L.) using RT-PCR and RACE. Codon usage analysis revealed that U- and A-ended codons were preferentially used in these two genes. Sequence analysis showed that the deduced amino acid sequences of CsFAD7 and CsFAD8 had high homology to plastidial omega-3 desaturases from other plant species. Expression analysis by real-time PCR revealed that both genes are tissue-specific and expressed the highest levels in shoots. Meanwhile, CsFAD7 and CsFAD8 responded to various abiotic stresses and hormones, but in very different manners. Taken together, these results suggest that CsFAD7 and CsFAD8 are both responsive to abiotic stress signals; however, they may play very different roles during stress tolerance in tea plants.