小麦光合功能期的遗传控制研究

Breeding for wheat varieties with improved photosynthetic efficiency is an important approach of high yielding wheat breeding. During the grain filling stage, suitably prolonging of photosynthetic duration is an important aspect of high photosynthetic breeding. Photosynthetic duration is largely determined by senescence processes. Wheat with shortened photosynthetic duration like early senescence or too extended photosynthetic duration for example late maturity will definitely not be extensively utilized in wheat production. However, late onset and fast rate of senescence that maintains long photosynthetic duration is one of the important characteristics for high photosynthetic breeding of wheat. Xiaoyan 81 released in 2005 is such a variety. Late onset of senescence make it have prolonged photosynthetic duration while fast rate of senescence make it remobilize more nutrition from leaves and stems to grains and results in high harvest index. Up to now, the genetic regulation of photosynthetic duration in wheat remains unclear. In this project, a sister line of Xiaoyan 81 with shortened photosynthetic duration named as EAL together with Xiaoyan 81 and other varieties will be used to explore the genetic control of photosynthetic duration. Single nucleotide polymorphism (SNP) array mapping, bulked segregant RNA-seq (BSR-Seq), association mapping, and virus-induced gene silencing (VIGS) via barley stripe mosaic virus (BSMV) will be used to study the genetic regulation of photosynthetic duration in wheat. This project is not only valuable for understanding the genetic control of photosynthetic duration but also it will produce molecular markers that may be potentially used for marker assisted selection of high photosynthetic wheat varieties with suitably prolonged photosynthetic duration.

光合功能期缩短的早衰与光合功能期过长的晚熟品系均会在育种早期被淘汰而难以在小麦生产中得到应用。衰老起始晚且衰老快进而维持较长时间的光合高值持续期是高光效小麦品种的重要特征。小偃81（冀审麦2005006号）具有这一特征，衰老起始晚光合功能期长，衰老快可使更多营养物质从茎叶转移至籽粒，进而获得较高收获指数。目前关于小麦光合功能期的遗传调控机制依然不清楚。本项目拟利用小偃81姊妹系光合功能期缩短的早衰系EAL和小偃81等研究小麦光合功能期的遗传调控机制。本项目计划利用全基因组小麦SNP芯片、BSR-seq等技术进行EAL精细定位，结合基因表达、EAL分子标记与120余份黄淮主栽小麦品种光合功能期的关联分析、病毒介导基因沉默、基因枪转化超表达等方法研究EAL候选基因及分子标记。本项目的开展将有助于解析小麦光合功能期的遗传调控机制，并为小麦高光效育种提供理论支撑和分子标记。

早衰往往导致光合时间缩短，进而引起作物减产。小麦育种群体中经常会发现早衰植株，这种表型是由遗传控制的。解析小麦早衰的分子基础，对认识小麦衰老的遗传调控和品种改良具有重要意义。本项目在前期“小偃54×8602”的育种群体中发现早衰系EAL的基础上，通过构建近等基因系和分离群体，结合BSA、BSR-seq和基因组重测序等方法对EAL基因开展了研究。结果显示，早衰系EAL除叶绿素含量、光合速率和光合代谢酶活力等下降外，激素合成基因的表达水平也发生了变化。例如，与赤霉素、脱落酸、油菜素内脂、生长素和细胞分裂素合成有关基因的表达受到抑制，而与乙烯、水杨酸、茉莉酸和独脚金内脂合成有关基因的表达受到诱导。早衰系与正常系混池的BSA和BSR-seq及“石新828×早衰系EAL”的F2分离群体的定位结果表明，EAL基因位于2D染色体26.41Mb区间。早衰系EAL和正常衰老系NL的重测序结果显示，早衰系EAL比正常衰老系NL增加了2473个SNP和21591个InDel，基因组序列变异主要发生于2D染色体区段。利用基于重测序开发的KASP和CAPS标记，将EAL基因定于2D染色体2.9Mb区间。序列分析发现，该区段内早衰系EAL的2D染色体序列存在大片段缺失，这与重测序结果一致。据此，我们推测2D染色体序列缺失是导致早衰发生的原因。此外，本项目还对一个类受体激酶基因TaRKL1进行了功能研究。结果显示，当该基因被沉默表达后，TaRKL1基因沉默株系的叶绿素含量和光合速率降低而衰老相关基因诱导表达。推测该基因参与调控小麦光合速率和过氧化氢代谢，还可能调控衰老基因表达。序列分析显示，TaRKL1在小麦品种中存在一个提前终止的SNP变异，该变异对小麦光合和衰老的影响还不清楚。