Genetic Breeding Of High Oleic Peanut By DsRNA Gene Silencing

Gene technology has provided plant breeders with powerful new tools for manipulating the composition of plant products to improve their nutritional value and functional properties. Double strands RNA produced post transcriptional gene silencing (PTGS) technique is being used to alter the relative proportion of the major fatty acids present in oil plants. Specifically designed genetic constructs resulted in gene silencing, such as inverted repeats that encode RNA having regions of self-complementarity, can reliably generate hairpin RNA (hpRNA) transcripts that invoke sequence-specific RNA degradation.The monounsaturated oleic acid could contribute to lowering the onset of coronary heart disease (CHD) by reducing blood low density lipoprotein (LDL) cholesterol and not change high density lipoprotein(HDL) cholesterol levels. Vegetable oil with elevated levels of oleic acid provides desirable properties related to both health benefits and stability characteristics. Therefore, one of the major goals for oilseed research is to improve the nutritive value of oilseeds by increasing the ratio of oleic acid to linoleic acid.In this study, we have employed hpRNA-mediated gene-silencing techniques to down-regulate the expression of key fatty acid desaturease gene of peanut, ahFAD2B, encoding microsomal ω6-desaturease and consequently modify the fatty acid composition of peanut oil (with high oleic oil content). The specific primers were designed according to the published sequence of ahFAD2B gene. The fragments of sense and antisense arms were amplified and ligated into an inverted repeat (IR) construct, which was driven by the soybean (Glycine max) lectin promoter. Hairpin RNA-encoding gene constructs targeted against ahFAD2B were transformed into peanut (Arachis hypogaea) by an Agrobacterium tumefacien-mediated method. Identification of transgenic plants by PCR revealed that the constructs had integrated in the plant genome. Fatty acid analysis of T1 seeds showed that the resulting down-regulation of the ahFAD2 gene substantially increased oleic acid content from the normal levels of 38% up to as high as 77%, and linoleic acid was significantly lowered from 36% to 9%. The modified high oleic peanut oil containing predominantly oleic acid (77%) and saturated acid (12%) is high quality edible oil with the stable characters and health benefit. This special peanut line obtained in this study may provide a basic material for genetic breeding of high oleic acid peanut with the stable genetic characters and high quality.