Genome-wide Investigation Of Acyl-lipid Metabolism And Caleosins In Oil Crops

Plant oil has close relationships with people’s daily life. The demanding of plant oil has been increased year by year. So that, prompt solutions about how to promote the oil content of oil crops are urgently needed currently. Besides fatty acids and triacylglycerols, the phospholipids, glycolipid, sphingolipids, oxylipins and waxes which are synthesized by fatty acids are all belongs to acyl-lipids. Those compounds that play crucial roles in various biological pathways have very close relationships with plant growth, so that they can significantly influence the lipid accumulation of plants.Rape, which contains turnip type rape which belongs to Brassica rapa and oilseed rape(Brassica napu), are the third largest oil crops in the world. Besides, it is also the most widely planted oil crop in China. Being classified as Brassica plants, the Brassica napus, its diploid parents Brassica rapa and Brassica oleracea are also belongs to the Cruciferae, which in line with Arabidopsis. Studies about acyl-lipid metabolism genes of model plant Arabidopsis have been carried out for many years. So that, based on the results of Arabidopsis acyl-lipid genes and transcript factors, studies about genome-wide analysis of acyl-lipid metabolism in brassica rapa, brassica oleracea and brassica napus are carried out in this study. This study aims at constructing an acyl-lipid database of rapes, which is a platform for lipid research, providing theoretical bases of oil content promotion and compound modification of rapes. It can also supply useful information related to oil accumulation and ingredient modification of other plants. Using caleosins from different plant species as good examples, their structural features, duplication modes and expression profiles are analyzed comprehensively, in order to lay the foundation of functional studies of caleosins. Such results can also be useful when studying other acyl-lipid metabolism gene family.Main content and conclusions of this paper are as follows:(1)Genome-wide analysis of Brassica plants acyl-lipid metabolism genes were carried out and an acyl-lipid database of rapes was constructed in this study. Based on 782 acyl-lipid genes and transcript factors, 1241, 1251 and 2556 genes and regulators in genome of Brassica rapa, Brassica oleracea, and Brassica napus were identified. Among them, almost all of the Brassica oleracea genes, 237 genes in Brassica rapa and 492 genes Brassica napus were herein identified for the first time. Based on the preference analysis of the number of homologous genes in Brassica rapa and Brassica oleracea according to a Arabidopsis thaliana, genes which were related to fatty acid synthesis, eukaryotic phospholipids synthesis in plastid, triacylglycerol biosynthesis and suberin biosynthesis tend to have multiple copies. Analysis of duplication pattern indicates that segmental duplication was the main form of the acyl-lipid gene family expansion, caused by whole genome duplication. Expression profile of three Brassica plants indicated that 110 genes and regulators in Brassica rapa, and 473 genes and regulators in Brassica napus were probably had closer relationships with acyl-lipid metabolism in seed; 15 genes in Brassica rapa, and 151 genes and regulators in Brassica napus were probably related to stress response. Moreover,6 ancient genes in Brassica napus might play more important roles in acyl-lipid metabolism. More than 500 genes and regulators in Brassica rapa showed differential expression in seed and other organ which can accumulate triacylglycerols(flower and seed), while 116 genes and 2 regulators in Brassica napus showed differential expression in seed and leaf.(2)Eight caleosins from Arabidopsis were analyzed comprehensively. Those genes were classified as H- and L- form according to the molecular weight and such result was also confirmed by motif analysis, multiple alignment and phylogenetic trees. Meanwhile, physicochemical properties, duplication pattern and expression profiles were also analyzed. Our result showed that the L-caleosins might be evolved from H-caleosins. Results also showed that segmental duplication and tandem duplication were main forms of gene family expansion. And the promoter analysis predicted that Arabidopsis caleosins might be participate in signal transduction and lipid accumulation.(3)Leguminosae caleosins were analyzed systematically. Twenty caleosins were identified from soybean, common bean and barrel medic. Duplication profiles indicated that tandem duplication was the main form of gene family expansion among those three legume plants. Combining the analysis towards conserved domain and expression patterns, we could infer that three of those caleosins might lost their functions, meanwhile, four genes like Gma CLO2 might play more important roles. In addition, the functions of four important caleosins were predicted.(4)Caleosins from Brassica plants were analyzed comprehensively. Fifty-one caleosins from Brassica plant and Arabidopsis lyrata were identified. Among them, thirty-one were firstly annotated. Segmental duplication was the main form of gene duplication according to our results. Analysis of conserved domain and evolution patterns indicated that the structures and physicochemical properties between H- and L- forms were diverse from each other. And such analysis also provided solid evidence to the prediction that L-forms may evolved from H-forms. Gene structure analysis indicated that caleosins in Brassica plants were highly conserved. Comprehensive analysis indicated that genes like Br CLO3-3 and Br CLO4-2 were worthy of further study while genes like Br CLO2 and Bo CLO8-2 were likely to lost their functions.