反义Trxs基因导入对弱筋小麦豫麦18淀粉积累及淀粉合成关键酶表达的影响

Effects of Antisense Thioredoxin s on Starch Accumulation and Expressions of Enzymes Related to Starch Synthesis in Weak-gluten Wheat Cultivar Yumai 18

以转反义硫氧还蛋白基因小麦TY18-99和TY18-100及其相应未转基因对照为材料,于2007—2009年通过盆栽试验系统研究了反义Trxs基因(anti-Trxs)导入对弱筋小麦豫麦18籽粒灌浆过程中淀粉积累、淀粉合成关键酶活性以及淀粉合成酶基因表达的影响。结果表明,反义Trxs基因对小麦籽粒淀粉积累有一定的正效应。2个转基因株系的总淀粉和支链淀粉的积累速率较对照显著提高;在整个籽粒形成过程中,反义Trxs基因导入显著提高了淀粉分支酶(SBE)活性。在籽粒灌浆中期和后期,反义Trxs基因导入显著提高了腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)和可溶性淀粉合酶(SSS)活性,降低了颗粒束缚型淀粉合酶(GBSS)活性。实时荧光定量RT-PCR分析表明,反义Trxs基因促进了AGPase、SBE I和SSS(SSS I、SSS II和SSS III)基因的表达,抑制了GBSS I基因的表达。上述结果说明,反义Trxs基因导入后促进了AGPase、SBE I和SSS基因的转录,从而使籽粒灌浆期间的淀粉积累速率发生了改变,最终显著提高了总淀粉和支链淀粉的含量,降低了直链淀粉含量,进而提高了淀粉的支/直比,这可能是转基因小麦淀粉品质改善和产量提高的主要原因。

To clarify the functional mechanisms of starch accumulation by the antisense-thioredoxin s（anti-Trxs）gene into wheat,we conducted a pot experiment using two transgenic wheat lines,TY18-99 and TY18-100,and their wild type ＂Yumai 18＂ from October 2007 to June 2009.The effects of the anti-Trxs on starch accumulation and key enzymes involved in starch synthesis were compared between the transgenic lines and the wild type.Results indicated that the rates of starch and amylopectin accumulations in grain were significantly higher in the transgenic lines than in the wild type.During the whole grain-filling period,activity of starch-branching enzyme（SBE）in the transgenic lines increased significantly by 49.2% compared with that in the wild type.At late grain-filling stage,activities of ADP-glucose pyrophosphorylase（AGPase）and soluble starch synthase（SSS）in the transgenic lines increased by 45.8% and 16.0%,respectively.However,activity of granule-bound starch synthase（GBSS）in the transgenic lines had no significant variation.The real-time RT-PCR assay indicated that the introduction of anti-Trxs resulted in increased expressions of SSS（SSS I,SSS II,and SSS III）,SBE I,and AGPase genes and reduction of GBSS I transcription.Therefore,the enhanced expressions of AGPase,SBE I,and SSS may be the main reason for increase in starch synthesis in anti-Trxs transgenic lines.