HbSGT1基因家族成员差异调控橡胶树白粉菌抗性机制研究

Powdery mildew is one of main leaf disease in rubber tree which inhibit tree growth and dry latex yield. SGT1 gene is broad-spectrum resistance gene which negatively regulation of powdery mildew resistance in many species. The identification of SGT1 gene in rubber tree is key problem in disease resistant breeding program. Recently, we found 4 HbSGT1 gene share high similarities with known SGT1 gene with disease resistance and their expression were upregulated by powdery mildew treatment. Our results suggested these SGT1 gene take part in the disease resistance response in rubber tree. Our purpose were clone and characterization of SGT1 gene family member in rubber tree based on transcriptome database; Identification of disease resistant SGT1 gene through system analyzed gene family expression under powdery, plant hormone, and H2O2 stress treatment; Analyzed sequence diverse in disease resistant and susceptible clones; Proved disease related SGT1 gene function in powdery mildew resistance by means of overexpression and silence SGT1 gene in rubber tree leaves with transient expression. These provided fundamental knowledge for elucidation of powdery mildew mechanism and breeding disease resistant clones through transgenic technique.

SGT1主要作为分子伴侣或调控泛素化等参与植物抗病反应，是植物R基因抗病信号的重要调控基因。橡胶树白粉病是重要的叶部病害，但其抗病分子机制尚不清楚。我们最近从橡胶树中克隆了SGT1a和b基因，发现其受白粉菌诱导差异表达，说明其参与橡胶树抗白粉病反应，并受白粉菌诱导显著上调表达，推测这些基因可能参与橡胶树对白粉菌的抗性反应。本项目利用橡胶树转录组数据库全面地克隆并鉴定橡胶树SGT1基因家族成员; 采用Q-PCR技术系统分析SGT1基因成员在白粉菌、植物激素、H2O2等胁迫处理后的基因表达模式，确定抗病相关SGT1基因；以橡胶树抗、感白粉病种质为材料，分析抗病相关SGT1基因在抗、感材料中的序列差异；并采用瞬间表达技术在橡胶树叶片中过表达和沉默抗病相关SGT1基因，证明抗病相关SGT1基因在抗白粉病中的功能。为进一步阐明其抗病机制并通过转基因技术培育巴西橡胶树抗巴西橡胶树抗白粉病品系奠定基础。

SGT1(The suppressor of the G2 allele of skp1)是植物R基因抗病信号的重要调控基因，以分子伴侣等作用方式参与植物抗病反应。针对橡胶树对白粉病这一重要的叶部病害抗病分子机制不清楚的问题。基于前期克隆了SGT1a和b基因，发现其受白粉菌诱导差异表达，提出HbSGT1a和HbSGT1b是橡胶树白粉病抗性的关键环节这一科学问题。本项目利用橡胶树基因组和转录组克隆并鉴定橡胶树HbSGT1a和HbSGT1b基因，首先证明其定位在细胞核；其次采用qRT-PCR技术系统分析SGT1基因成员在不同组织、白粉菌侵染时期、植物激素和干旱等逆境胁迫处理后的基因表达模式，确定抗病相关基因为HbSGT1b；进一步以橡胶树抗、感白粉病种质为材料，分析抗病相关SGT1基因在抗、感材料中表达规律、相关性和序列差异，用于分子标记辅助选择育种材料筛选；随后采用转基因技术在拟南芥Col-0，atsgt1a和atsgt1b分别过表达HbSGT1a和HbSGT1b，证明其在橡胶树白粉病抗性和生长发育中的功能。与此同时，我们克隆筛选生长素、钙调蛋白依赖的蛋白激酶相关基因HbJAR1，HbCRK1和HbHSP90家族成员，并采用酵母双杂交证明HbSGT1a、HbSGT1b和HbHSP90家族成员体内两两互作。最后，我们提出白粉菌侵染通过机械伤害、SA等激素信号上调HbSGT1b基因表达，与HbHSP90互作后提高白粉病抗性和生长发育的分子机制。本研究为进一步阐明其抗病机制并通过转基因技术培育巴西橡胶树抗白粉病品系打下坚实基础。