Cloning and expression analysis of three cDNAs encoding omega-3 fatty acid desaturases from Descurainia sophia.

Three cDNAs of DsFAD3, DsFAD7 and DsFAD8, encoding omega-3 fatty acid desaturases, which are the key enzymes for the conversion of linoleic to alpha-linolenic acid (18:3n-3), were isolated from Descurainia sophia using RACE-PCR. Tissue-specific expression analysis revealed that DsFAD3 and DsFAD7 genes were expressed in all tissues and at a high level in stems, leaves and young siliques, whereas DsFAD8 was moderately expressed in photosynthetic tissues including stems, leaves and young siliques. All three genes were significantly induced by wounding stress and DsFAD3 and DsFAD7 transcript levels were down-regulated by cold, whereas DsFAD8 was increased upon cold stress.