Omega-3 fatty acid desaturase genes isolated from purslane (Portulaca oleracea L.): expression in different tissues and response to cold and wound stress.

Two full-length cDNA clones PoleFAD7 and PoleFAD8, encoding plastidial omega-3 fatty acid desaturases were isolated from purslane (Portulaca oleracea). The encoded enzymes convert linoleic to alpha-linolenic acid (C18:3n-3). Three histidine clusters characteristic of fatty acid desaturases, a putative chloroplast transit peptide in the N-terminal, and three putative transmembrane domains were identified in the sequence. Both genes were expressed in all analyzed tissues showing different levels of expression. PoleFAD7 was up-regulated by wounding but not by low temperature. PoleFAD8 was up-regulated by cold stress but not by wounding. Total fatty acid and linolenic acid content were higher both, in wounded and intact leaves of plants exposed to low temperature.