文冠果种仁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 Kernel Development of Xanthoceras sorbifolium

为探讨文冠果种仁油脂合成积累与源汇基因表达的关系,以品系‘12-03’4个不同发育期(6月22日,7月6日, 7月19日和8月1日)的种仁为材料,利用氯仿甲醇法测定含油率,q RT-PCR方法分析油脂合成源基因(GPD1)和汇基因(DGAT1, DGAT2)在种仁中的表达差异及其对文冠果油脂快速合成积累的影响。结果表明:(1)文冠果种仁发育期,含油率呈快速上升趋势,从6月22日到8月1日的40 d,由6.69%上升到45.10%;(2)源基因GPD1和汇基因DGAT1与DGAT2在种仁发育前期中的表达量均呈快速上升趋势,且GPD1和DGAT2的表达量在7月19日达到最高值;随后的种仁成熟期,GPD1表达量迅速降低,而DGAT1的表达量则略有上升。源基因GPD1在种仁发育前期高表达,促进合成更多的TAG前体G3P,而种仁发育成熟期高表达的汇基因DGAT1和DGAT2则促进了TAG的持续积累。文冠果种仁发育期的油脂快速合成积累源于调控油脂合成的关键源基因(GPD1)和汇基因(DGAT1)的协同高表达,源基因GPD1表达量增加2.11倍和汇基因DGAT1表达量增加4.63倍,促成种仁含油量增加6.2倍。本研究可为理解木本油料种子油脂快速合成积累机制提供理论依据。

The objective of this study was to explore the relationship between lipid biosynthesis and expression of source and sink genes during different developmental stages ofXanthoceras sorbifolium kernel. The kernels of line ＇12-03＇, harvested at June 22, July 6, July 19, and August I was selected as sample materials. The oil contents in the kernels were tested by the method of chloroform methanol, and the differential expressions of source gene （GPD1） and sink genes （DGA T1, DGA T2） involved in lipid biosynthesis and accumulation of kernels were determi- ned using qRT-PCR, and the effects of these three genes on lipid biosynthesis and accumulation were analyzed. The results showed that the kernel oil content had a rapid upward trend during kernel development, which incre-ased from 6.69% to 45.10% in only 40 days from June 22 to August 1. The expressions of source gene GPD1 and sink genes of DGA T1 and DGA T2 rose rapidly during early kernel development, and the expression of ＇DGA TI＇ and ＇DGA T2＇ reached the highest value at July 19. After this, in the mature period of kernel, GPD1 expression decreased rapidly, but the DGA T1 expression was up slightly. The high expressions of source gene GPD1 contribut- ed to the synthesis of more G3P of TAG precursor in early kernel development, and the high expressions of sink genes of DGA T1 and DGA T2 promoted rapid TAG accumulation in the mature period of kernel. The rapid lipid biosynthesis and accumulation in kernel of X. sorbifolium was from coordinated high expression of source gene GPD1 and sink genes of DGA T1 and DGA T2. The 2.11 times increase of relative expression value of source gene GPD1 and the 4.63 times increase of sink gene DGA T1 leaded to 6.2 times increase of kernel oil content. These results could provide scientific basis for understanding lipid rapid biosynthesis and accumulation mechanism in seeds of woody-oil trees.