油茶种子发育期油脂合成积累的源汇基因协同表达

Coordinated Expression of Source and Sink Genes Involved in Lipid Biosynthesis and Accumulation during Camellia oleifera Seed Development

为探讨油茶种子油脂的合成积累与源汇基因表达间的关系,以高油品系‘MY003’和低油品系‘MY008’的不同发育时期(6月2日、7月4日、8月5日、9月3日)种子为材料,利用氯仿甲醇法测定含油率,采用qRT-PCR技术分析油脂合成源基因(GPD1)和汇基因(DGAT1和DGAT2)在高低油种子间的表达差异及其对油脂合成积累的影响,为进一步研究油茶种子油脂合成积累的分子机制提供理论依据。结果显示:(1)油茶种子含油率均处于逐渐上升趋势(0.16%~24.1%),并在7月4日以后开始迅速上升,且‘MY003’种子含油率一直高于‘MY008’。(2)在‘MY003’种子中GPD1、DGAT1和DGAT2基因表达量均明显高于‘MY008’,DGAT1和DGAT2在源基因GPD1高水平表达后仍出现表达高峰;源基因GPD1在种子发育初期高表达,促进了TAG前体G3P的高效合成,而汇基因DGAT1和DGAT2在种子发育后期高表达,则促进了TAG的高效积累,GPD1与DGAT1、DGAT2之间呈正相关关系。研究表明,油茶种子油脂的合成积累来源于源基因GPD1和汇基因DGAT1与DGAT2的协同高表达。

The objective of this study is to explore the relationship between lipid biosynthesis and expression of source and sink genes during Camellia oleifera seed development.The line“MY003”with high oil content in the seeds and the line“MY008”with low oil content in the seeds were selected as sample trees.These seeds were harvested at June2,July4,August5,and September3.The oil contents in the seeds were determined by the method of chloroform methanol.The differential expression of source gene(GPD1)and sink genes(DGAT1and DGAT2)involved in lipid biosynthesis between high and low oil content lines were determined using qRT PCR,and the effects of these three genes on lipid biosynthesis and accumulation were analyzed.The results showed that:(1)the oil contents in the seeds of two lines were in a gradual upward trend(0.16%-24.1%),and it began to rise rapidly after July4.The oil contents in the seeds of“MY003”were higher than that of“MY008”at all stages;(2)The peak values of GPD1,DGAT1and DGAT2expression in the seeds of“MY003”were significantly higher than that of“MY008”during seed development.The expression of DGAT1and DGAT2still appeared peak values after the high level expression of GPD1,but the peaks of GPD1gene appeared in the early period of seed development,and the peaks of DGAT1and DGAT2genes appeared in the later period of seed development.The high expression of source gene GPD1contributed to promote the TAG precursor G3P high synthesis efficiency in the early of seed development,and the high expression of sink genes DGAT1and DGAT accelerated high TAG accumulation in later period of seed development.There were positively correlated relationships in expressions among GPD1,DGAT1and DGAT2genes.Thus,the coordinated expression of source gene GPD1and sink genes DGAT1and DGAT2resulted in the lipid biosynthesis and accumulation in C.oleifera seeds.These results could provide scientific bases for studying on molecular mechanism of lipid biosynthesis in the seeds of C.oleifera.