Katral Ashvinkumar, Muthusamy Vignesh, Zunjare Rajkumar U, Chhabra Rashmi, Maman Shalma, Yadava Devendra K, Hossain Firoz
Division of Genetics, ICAR-Indian Agricultural Research Institute, New Delhi, India.
Front Nutr. 2022 May 6;9:845255. doi: 10.3389/fnut.2022.845255. eCollection 2022.
Edible oil with lower saturated fatty acids is desired for perceived quality and health benefits to humans and livestock. gene encoding acyl-ACP thioesterase is a key player in the conversion of palmitic acid to oleic acid, thereby modifying the ratio of saturated to unsaturated fatty acids in maize kernels. The present investigation characterised the full-length sequence of the gene (4.63 kb) in two mutants () and eight wild-types () inbreds to study allelic variation, gene-based diversity, phylogenetic-relationship, protein-modelling, and molecular-docking to identify novel candidates for modification of fatty acid profile. Sequence alignment revealed wide genomic variability for among the inbreds; identified five novel SNPs and two InDels that clearly differentiated the wild-type and mutant genotypes. Gene-based diversity using 11-InDel markers categorised 48-diverse maize-inbreds into two-clusters. The majority of mutant and wild-type inbreds were grouped in separate clusters and led to the generation of 41 haplotypes. Genetic relationship of maize gene with orthologues among 40 accessions of 12 oilseed-crops using both nucleotide and protein sequence clustered maize, soybean, sunflower, opium-poppy, , quinoa, and prunus species into one cluster; and brassica, camelina, and arabidopsis into the different cluster. The clustering pattern revealed that the plant oil with higher unsaturated fatty acids, particularly oleic, linoleic, and linolenic acids grouped together in one cluster and higher proportions of other fractions like arachidic, eicosenoic, and erucic acids grouped in another cluster. Physico-chemical properties highlighted more similarity between maize and 29 orthologue proteins, but orthologues were found to have better thermostability. Homology models have been developed for maize mutant and wild-type inbreds using (PDB ID: 5x04) as a template. Predicted protein models possessed optimum confidence-score and RMSD values and validated stability via., Ramachandran plots. Molecular docking indicated most of the interactions of protein-ligand were having similar binding-affinity due to the broader specificity of fatty acyl-ACP thioesterases and the presence of conserved-domains across crops. This is the first report on the comprehensive molecular characterisation of the gene in maize and various orthologues. The information generated here provided new insights into the genetic diversity of gene which can be utilised for the enhanced nutritive value of oil in the breeding programme.
人们期望食用饱和脂肪酸含量较低的食用油，因为其对人类和牲畜的感知品质及健康有益。编码酰基 - ACP硫酯酶的基因是将棕榈酸转化为油酸的关键因素，从而改变玉米籽粒中饱和脂肪酸与不饱和脂肪酸的比例。本研究对两个突变体和八个野生型自交系中的该基因全长序列（4.63 kb）进行了表征，以研究等位基因变异、基于基因的多样性、系统发育关系、蛋白质建模和分子对接，从而确定用于修饰脂肪酸谱的新候选基因。序列比对揭示了自交系中该基因存在广泛的基因组变异性；鉴定出五个新的单核苷酸多态性（SNP）和两个插入缺失（InDel），它们能清晰地区分野生型和突变型基因型。使用11个InDel标记进行的基于基因的多样性分析将48个不同的玉米自交系分为两个簇。大多数突变型和野生型自交系被归为不同的簇，并产生了41个单倍型。利用核苷酸和蛋白质序列对12种油料作物的40个种质中玉米该基因的直系同源物进行遗传关系分析，结果将玉米、大豆、向日葵、罂粟、藜麦和李属物种归为一个簇；而芸苔属、亚麻荠属和拟南芥属归为另一个簇。聚类模式表明，不饱和脂肪酸含量较高，特别是油酸、亚油酸和亚麻酸含量较高的植物油归为一个簇，而花生酸、二十碳烯酸和芥酸等其他成分比例较高的植物油归为另一个簇。物理化学性质突出了玉米与29个直系同源蛋白之间的更多相似性，但直系同源蛋白具有更好的热稳定性。以（蛋白质数据银行ID：5x04）为模板，为玉米突变体和野生型自交系构建了同源模型。预测的蛋白质模型具有最佳的置信度得分和均方根偏差（RMSD）值，并通过拉氏图验证了稳定性。分子对接表明，由于脂肪酰 - ACP硫酯酶具有更广泛的特异性以及不同作物中存在保守结构域，大多数蛋白质 - 配体相互作用具有相似的结合亲和力。这是关于玉米中该基因及其各种直系同源物的全面分子表征的首次报道。此处生成的信息为该基因的遗传多样性提供了新的见解，可用于在育种计划中提高油的营养价值。
