PubMed · 11462354
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S Yamaguchi. 2001. [Aciduria, glutaric (type 2)].. https://pubmed.ncbi.nlm.nih.gov/11462354/
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cDNA clones encoding cytochrome b(5) fusion desaturases were isolated from Primula cortusoides L. and Primula luteola Ruprecht, species previously shown to preferentially accumulate either n-6 or n-3 Delta6-desaturated fatty acids, respectively. Functional characterisation of these desaturases in yeast revealed that the recombinant Primula enzymes displayed substrate preferences, resulting in the predominant synthesis of either gamma-linolenic acid (n-6) or stearidonic acid (n-3). Independent expression of the two Primula desaturases in transgenic Arabidopsis thaliana confirmed these results, with gamma-linolenic acid and stearidonic acid accumulating in both leaf and seed tissues to different levels, depending on the substrate specificity of the desaturase. Targeted lipid analysis of transgenic Arabidopsis lines revealed the presence of Delta6-desaturated fatty acids in the acyl-CoA pools of leaf but not seed tissue. The implications for the transgenic synthesis of C(20) polyunsaturated fatty acids via the elongation of Delta6-desaturated fatty acids are discussed, as is the potential of using Primula desaturases in the synthesis of C(18) n-3 polyunsaturated fatty acids such as stearidonic acid.
Plastid omega-3 fatty acid desaturase catalyzes the conversion of dienoic fatty acids (16:2 and 18:2) to trienoic fatty acids (16:3 and alpha-18:3) in glycerolipids which are the main constituents of chloroplast membranes. We produced transgenic tobacco plants that express the transcript of a double-stranded RNA (dsRNA) of tobacco plastid omega-3 fatty acid desaturase gene, NtFAD7. In these transgenic plants, 16:3 and alpha-18:3 content in leaves decreased to less than 2.7% and 7.5-10.4%, respectively, when compared with the control plant. The steady-state NtFAD7 mRNA was not detected in the transgenic plants. These results indicate that down-regulation of the transcript level in the NtFAD7 by introduction of NtFAD7 dsRNA constructs is useful to decrease the trienoic fatty acid contents of the vegetative tissues in higher plants.
All higher plants contain at least one microsomal omega-6 desaturase (FAD2), which inserts a double bond between the carbons 12 and 13 of monounsaturated oleic acid to generate polyunsaturated linoleic acid and controls most of the polyunsaturated lipid synthesis in plant cells. RNA interference can be used to silence endogenous genes by effective degradation of target transcripts. To investigate development-related silencing of the FAD2, fatty acid composition was analyzed in the context of leaf expansion in FAD2-silenced tobacco lines obtained by RNA interference technology. We observed that the increased oleate level in unexpanded leaves due to FAD2-silencing receded significantly in fully expanded leaves. The mechanism involved in this interesting phenomenon was investigated by analyses of individual lipid proportion, fatty acid composition of individual lipids, and FAD2 transcript level in the transgenic leaves at different expansion stages. Data revealed that the expansion-related FAD2-silencing effect was not due to rebound of FAD2 transcript, but rather probably due to chloroplast development with leaf expansion.