College of Agronomy and Biotechnology, Chongqing Rapeseed Engineering Research Center, Academy of Agricultural Sciences, Southwest University, Chongqing, 400715, China.
Biochem Genet. 2021 Oct;59(5):1295-1310. doi: 10.1007/s10528-021-10063-w. Epub 2021 Apr 1.
Plastidial Δ12 fatty acid desaturase (FAD6) is a key enzyme for linoleic acid (LA) and α-linolenic acid (ALA) biosynthesis. Chia (Salvia hispanica L.) is a revived omega-3 plant source that is richest in ALA level. In this study, based on the RACE method, one full-length cDNA sequence encoding FAD6, named ShFAD6, was isolated from chia. There exist three alternative transcription start sites and five alternative poly(A) tailing sites in ShFAD6. The 5'UTR of ShFAD6 contains a purine-stretch of 44 bp. ShFAD6 has an ORF of 1335 bp encoding a 444 aa protein of 51.33 kDa. ShFAD6 contains a conserved Delta12-FADS-like domain together with three strong trans-membrane helices and three histidine motifs. There also exists a chloroplast transmit peptide in ShFAD6 N-terminal. Phylogenetic analyses validated its identity of dicot FAD6 protein and suggested some critical evolutionary features of plant FAD6 genes. Heterologous yeast expression confirmed the catalytic activity of ShFAD6. The qRT-PCR assay showed that ShFAD6 is mainly expressed in leaves, stems, flowers, buds and early-stage seeds, and also responded to various stresses and hormone treatments. Under Sclerotinia infection, qRT-PCR and fluorescence imaging illustrated the possible correlation of ShFAD6 expression and photosynthesis. This study provides insight for further function study of ShFAD6 in oil quality improvement in staple oilseed crops as well as stress response and adaptation in plants.
质体 Δ12 脂肪酸去饱和酶（FAD6）是亚油酸（LA）和α-亚麻酸（ALA）生物合成的关键酶。奇亚（Salvia hispanica L.）是一种复兴的ω-3 植物来源，ALA 含量最丰富。在这项研究中，基于 RACE 方法，从奇亚中分离出一个编码 FAD6 的全长 cDNA 序列，命名为 ShFAD6。ShFAD6 存在三个替代转录起始位点和五个替代 poly(A)尾化位点。ShFAD6 的 5'UTR 含有 44 bp 的嘌呤延伸。ShFAD6 的 ORF 长 1335 bp，编码一个 444 个氨基酸的 51.33 kDa 蛋白质。ShFAD6 含有一个保守的 Delta12-FADS 样结构域，以及三个强跨膜螺旋和三个组氨酸基序。ShFAD6 的 N 端还存在一个质体转运肽。系统发育分析验证了其作为双子叶植物 FAD6 蛋白的身份，并提出了植物 FAD6 基因的一些关键进化特征。异源酵母表达证实了 ShFAD6 的催化活性。qRT-PCR 检测表明，ShFAD6 主要在叶片、茎、花、芽和早期种子中表达，也对各种胁迫和激素处理有反应。在核盘菌感染下，qRT-PCR 和荧光成像表明 ShFAD6 表达与光合作用之间可能存在相关性。这项研究为进一步研究 ShFAD6 在提高主要油料作物油质以及植物应对和适应胁迫方面的功能提供了依据。
