Differential transcriptional activity of SAD, FAD2 and FAD3 desaturase genes in developing seeds of linseed contributes to varietal variation in a-linolenic acid content Ashwini V. Rajwade a, Narendra Y. Kadoo a, Sanjay P. Borikar b, Abhay M. Harsulkar c, Prakash B. Ghorpade d, Vidya S. Gupta a,⇑ a
Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411 008, India Organic Chemistry Division, CSIR-National Chemical Laboratory, Pune 411 008, India c Interactive Research School for Health Affairs, Bharati Vidyapeeth University, Pune 411 043, India d AICRP on Linseed, College of Agriculture, Nagpur 440 001, India b
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Article history: Received 19 August 2013 Received in revised form 15 November 2013 Available online 28 December 2013 Keywords: Linseed Flax ALA Fatty acid desaturases Fatty acids Gene expression
a b s t r a c t Linseed or ﬂax (Linum usitatissimum L.) varieties differ markedly in their seed a-linolenic acid (ALA) levels. Fatty acid desaturases play a key role in accumulating ALA in seed. We performed fatty acid (FA) proﬁling of various seed developmental stages of ten Indian linseed varieties including one mutant variety. Depending on their ALA contents, these varieties were grouped under high ALA and low ALA groups. Transcript proﬁling of six microsomal desaturase genes (SAD1, SAD2, FAD2, FAD2-2, FAD3A and FAD3B), which act sequentially in the fatty acid desaturation pathway, was performed using real-time PCR. We observed gene speciﬁc as well as temporal expression pattern for all the desaturases and their differential expression proﬁles corresponded well with the variation in FA accumulation in the two groups. Our study points to efﬁcient conversion of intermediate FAs [stearic (SA), oleic (OA) and linoleic acids (LA)] to the ﬁnal product, ALA, due to efﬁcient action of all the desaturases in high ALA group. While in the low ALA group, even though the initial conversion up to OA was efﬁcient, later conversions up to ALA seemed to be inefﬁcient, leading to higher accumulation of OA and LA instead of ALA. We sequenced the six desaturase genes from the ten varieties and observed that variation in the amino acid (AA) sequences of desaturases was not responsible for differential ALA accumulation, except in the mutant variety TL23 with very low (45% ALA) and low ALA (with
Differential transcriptional activity of SAD, FAD2 and FAD3 desaturase genes in developing seeds of linseed contributes to varietal variation in α-linolenic acid content.
Linseed or flax (Linum usitatissimum L.) varieties differ markedly in their seed α-linolenic acid (ALA) levels. Fatty acid desaturases play a key role...