Fang Jingjing, Zhu Weiqi, Tong Yiping
Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China.
National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Plants (Basel). 2020 Jul 3;9(7):840. doi: 10.3390/plants9070840.
Brassinosteroid (BR)-deficient or -insensitive mutants exhibited altered plant architecture with the potential to impact yield, the underlying physiological and molecular mechanisms are still to be explored. In this study, we cloned three BR receptor homologous genes and from hexaploid wheat ( L.) and further isolated the deletion mutants from the ion beam-induced mutants of variety Xiaoyan81, and in which the expression of total receptor was significantly decreased. The knock-down mutants exhibited relatively erect leaves and a significant decrease in the 1000-grain weight. Further studies showed that knock-down mutants showed a significant reduction in photosynthetic rate during the whole grain-filling stage. knock-down plants generated by deletion or using virus-induced gene silencing exhibited the reduction in the efficiency of photosystem II (PSII) (/, Φ and electron transport rate, ETR) especially under high light and high temperature stresses. The 24-epibrassinolide (EBR) treatment increased CO assimilation rate in the wild type under both normal and high light and high temperature stresses conditions, but this increasing effect was not observed in the knock-down mutants. Meanwhile, the expression levels of BR biosynthetic genes including , and is not decreased or decreased to a lesser extent in the knock-down mutants after EBR treatment. These results suggested that is required for maintaining photosynthesis and tolerance to high light and high temperature stresses both of which are important for grain yield and will be a possible engineered target to control plant photosynthesis and yields in wheat.
油菜素内酯（BR）缺陷或不敏感突变体表现出改变的植株形态，有可能影响产量，但其潜在的生理和分子机制仍有待探索。在本研究中，我们从六倍体小麦（Triticum aestivum L.）中克隆了三个BR受体同源基因TaBRI1-1、TaBRI1-2和TaBRI1-3，并从小偃81的离子束诱导突变体中进一步分离出TaBRI1-3缺失突变体，其中总受体TaBRI1的表达显著降低。TaBRI1敲除突变体表现出叶片相对直立，千粒重显著降低。进一步研究表明，TaBRI1敲除突变体在整个灌浆期光合速率显著降低。通过TaBRI1缺失或利用病毒诱导基因沉默产生的TaBRI1敲除植株在光系统II（PSII）效率（Fv/Fm、ΦPSII和电子传递速率，ETR）方面表现出降低，尤其是在高光和高温胁迫下。24-表油菜素内酯（EBR）处理在正常、高光和高温胁迫条件下均提高了野生型的CO2同化率，但在TaBRI1敲除突变体中未观察到这种增加效应。同时，EBR处理后，TaBRI1敲除突变体中包括DWF4、CPD和ROT3在内的BR生物合成基因的表达水平未降低或降低程度较小。这些结果表明，TaBRI1是维持光合作用以及对高光和高温胁迫耐受性所必需的，而这两者对籽粒产量都很重要，并且将是控制小麦植株光合作用和产量的一个可能的工程靶点。
