Molecular cloning and characterization of two plastidial Δ12 fatty acid desaturase cDNAs from Perilla frutescens

The plastidial delta-12 fatty acid desaturase (FAD6) plays a key role in linoleic acid (LA) and α-linolenic acid (ALA) biosynthesis. Perilla ( Perilla frutescens ) is an important oilseed crop with the highest ALA level. Here, using RACE PCR, two FAD6 cDNAs were cloned from perilla: the 1726 bp PfFAD6 and the 1881 bp PfFAD6’ . PfFAD6 encodes a 443 aa protein, while PfFAD6’ is a pseudogene caused by premature stop codon mutation. N-terminal of PfFAD6 has a chloroplast transit peptide. PfFAD6 harbors an omega-6 FAD conserved domain, 2 trans-membrane helices and 3 histidine boxes. Phylogenetic analysis revealed some important evolutionary features of PfFAD6 and other plant FAD6 genes. Heterologous yeast expression showed that protein encoded by PfFAD6 can catalyze the production of LA. PfFAD6 was expressed in various organs at different levels, and responded to multiple biotic/abiotic stresses. The qRT-PCR assay and fluorescence imaging showed the correlation of PfFAD6 transcripts and photosynthetic activity under Sclerotinia infection. This study will lay a foundation for further function study of PfFAD6 in quality improvement in oilseed crops and plant-stress response.