Frontiers in Plant Science (Jul 2012)
Modification of seed oil composition in Arabidopsis by artificial microRNA-mediated gene silencing
Abstract
Various post transcriptional gene silencing (PTGS) strategies have been developed and exploited to study gene function or engineer disease resistance. The recently-developed artificial microRNA (amiRNA) strategy is an alternative method of effectively silencing target genes. The ∆12-desaturase (FAD2), Fatty acid elongase (FAE1) and Fatty acyl-ACP thioesterase B (FATB) were targeted with amiR159b-based constructs in Arabidopsis thaliana to evaluate changes in oil composition when expressed with the seed-specific Brassica napus truncated napin (FP1) promoter. Fatty acid profiles from transgenic homozygous seeds reveal that the targeted genes were silenced. The down-regulation of the AtFAD-2 gene substantially increased oleic acid from the normal levels of ~15% to as high as 63.3% and reduced total PUFA content (18:2∆9,12+18:3∆9,12,15) from 44.8% to 4.7%. ∆12-desaturase activity was reduced to levels as low as those in the null fad-2-1 and fad-2-2 mutants. Silencing of the FAE-1 gene resulted in the reduction of eicosenoic acid (20:1∆11) to 1.9+1.0% from 15% and silencing of FATB resulted in the reduction of palmitic acid (16:0) to 4.4+0.5% from 8.0%. Reduction in FATB activity is comparable with a FATB-knock out mutant. These results demonstrate for the first time amiR159b constructs targeted against three endogenous seed-expressed genes are clearly able to down regulate and generate genotypic changes that are inherited stably over three generations.
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