百合转录辅激活因子LlMBF1c调控百合耐热性的机理解析

Lily holds a high market share in cut flowers industry worldwide, which is widely cultivated in China. As a general rule, lilies are well adapted to cool and humid climatic conditions and most of them are sensitive to high temperature. Exposure to high temperature during summer may lead to a reduction in cut-flower quality and degeneration of the bulb, consequently restrict the year-round production of lily. A growing literature confirms that MBF1c (Multiprotein Bridging Factor 1c), also known as Transcriptional co-activator, plays an important role in thermotolerance. Earlier studies have revealed that MBF1c was regulated by class A HSF, however our findings implied that MBF1c may be in the upstream of HSFA in response to heat stress. Here we want to isolate homologous MBF1c (LlMBF1c) from the thermotolerant cultivar ‘White Heaven’ of lily, and to detect its expression, to analyze the relationship of LlMBF1c and LlHSFA1 in the heat shock signal transduction network, to investigate its thermotolerant function through overexpression in Arabidopsis and lily, to find the downstream genes and target HSFs for LlMBF1c. Taken together, these results can provide evidences for function and mechanisms of LlMBF1c in thermotolerant regulation of lily. This work lays a foundation of theory and provides technique for improving thermotolerance of lily via genetic engineering.

百合是国际花卉市场中重要的切花，在我国被广泛栽培。百合性喜冷凉、湿润气候，不耐热。夏季高温会导致百合切花产量、品质下降和种球退化，是制约我国百合周年生产的主要限制因素。研究表明，植物转录辅激活因子MBF1c是植物热激信号转导网络中的关键节点，在植物耐热性的转录水平调控中发挥重要作用。以往的研究表明，MBF1c受A类HSF调控，但我们的研究发现MBF1c可能在A类HSF的上游参与了植物的热激响应。本研究拟从百合耐热品种‘White Heaven’中克隆MBF1c基因，检测其表达特性，分析LlMBF1c对LlHSFA1启动子的结合，在拟南芥中过表达验证其耐热功能，并确定LlMBF1c调控的下游基因和HSF靶基因，将鉴定功能的LlMBF1c基因转化百合进一步分析耐热性，从而明确LlMBF1c在百合耐热性调节方面的功能和解析其作用机制，为采用基因工程技术改良百合的耐热性奠定理论基础和提供技术支撑。

百合是国际花卉市场中重要的切花，在我国被广泛栽培。百合性喜冷凉、湿润气候，不耐热。夏季高温会导致百合产量、品质下降和种球退化，是制约我国百合周年生产的主要限制因素。本项目以植物热激信号转导网络中的关键节点MBF1c为切入点，分析其在百合耐热性方面的功能及转录调控机制。主要结果为：以麝香百合杂种系品种‘白天堂’为试验材料，从中分离得到LlMBF1c基因，LlMBF1c在叶中的表达量最高，根中次之，鳞茎中最低，LlMBF1c的表达受热激诱导。亚细胞定位结果表明LlMBF1c可能介导了热激信号由细胞质向细胞核的转导。过表达LlMBF1c基因拟南芥的耐热性明显强于野生型，热胁迫下转基因植株中AtHsfA1b的表达量显著高于野生型。酵母单杂交分析表明LlMBF1c与LlHsfA1、AtHsfA1b的启动子具有结合活性。研究结果表明MBF1c可能通过调控A类HSF的表达参与了百合的热激响应。本项目初步探明了LlMBF1c在百合耐热性调节方面的功能和解析了其转录调控机制，为采用基因工程技术改良百合的耐热性奠定了理论基础。