PtoWOX11/12a通过生长素诱导的磷酸化来调控杨树不定根向重力弯曲生长的机制研究

The growth angle between adventitious root and cutting in cottage propagation determines adventitious root growth direction that can affect anchorage to the soil as well as for water and minerals supply in forestry. Now, studies have shown that asymmetric distribution of auxin in the lower and upper part of root tip play critical role in the root gravitropic growth. However, the mechanism of auxin controlled root curvature growth is poorly understood. Recently, the applicant found that PtoWOX11/12a positively regulated adventitious root gravitropic growth in poplar, and PtoWOX11/12a was phosphorylated by auxin in vitro. So the applicant proposed that PtoWOX11/12a was phosphorylated by asymmetrical auxin in vivo to regulate adventitious root curvature growth response to gravity in poplar, but the mechanism is unclear. So, in this study the spatio-temporal expression pattern of PtoWOX11/12a will be uncovered to understand how auxin and gravity regulated PtoWOX11/12a expression on adventitious root curvature growth in poplar. Furthermore, the dynamic phosphorylation of PtoWOX11/12a and phosphorylation site will be analyzed to understand how auxin and gravity regulate phosphorylation of PtoWOX11/12a. Altogether, this project will elucidate the mechanism and function of PtoWOX11/12a phosphorylation to provide molecular basis and technical approaches for genetic improvement of poplar and other forest tree.

在林木扦插繁殖中，不定根和插穗间的夹角决定不定根的生长方向而影响林木固着土壤，摄取水分、矿质营养和抵御环境胁迫的能力。目前研究认为，不对称分布的生长素在不定根向重力弯曲生长中起关键作用，从而决定根的生长角度。但生长素调控根尖弯曲生长的机制尚不明确。申请者在前期研究中发现PtoWOX11/12a正调控杨树不定根的向重力生长，且生长素可诱导PtoWOX11/12a的磷酸化。故申请者提出PtoWOX11/12a通过生长素诱导的磷酸化来调控根尖向重力弯曲生长，但其机制有待深入研究。故本项目将深入研究杨树不定根向重力弯曲生长过程中PtoWOX11/12a的表达模式、生长素对PtoWOX11/12a磷酸化修饰及其功能。总之，本项目将阐明PtoWOX11/12a通过生长素诱导的磷酸化的功能及生物学机制，为林木根系的遗传改良提供理论和技术基础。

1基于前期研究，本项目提出了PtoWOX11/12a为生长素调控根尖弯曲生长的正调控因子，并且对其调控机制进行深入研究，主要包含了以下2个方面的内容：.1，PtoWOX11/12a在不定根弯曲生长的功能以及潜在机制。.通过对重力响应的关键调控因子LZY基因的共表达网络分析，鉴定出一批潜在可能参与不定根生长。通过公共数据库的表达差异分析，发现出PtoWOX11/12a具有特异表达的性质，表明了PtoWOX11/12a是潜在的不定根重力响应的调控因子。通过qPCR和GUS染色发现PtoWOX11/12a具有根冠表达特异性，其表达和不定根的弯曲相一致。表型和功能分析表明了过表达PtoWOX11/12a促进不定根向地生长，而RNAi和过表达PtoWOX11/12asrdx的不定根向地生长出现抑制；重力响应实验也表明了PtoWOX11/12a是重力响应的调控因子。组织解剖学观察表明PtoWOX11/12a维持了根冠细胞细胞柱状细胞处于未脱落状态，从而促进了柱状细胞对重力的响应。转录组分析表明了PtoWOX11/12a可能通过调控乙烯的合成参与不定根对重力的响应。总之，本项目研究了PtoWOX11/12a在不定根向重力生长中的功能和机制分析，PtoWOX11/12a为不定根对重力响应的关键调控因子。.2，PtoWOX11/12a在不定根弯曲生长过程中对侧根起始的功能和潜在机制。.不定根向地生长和不定根根系的形成是不定根发育中的两个问题，本项目进一步研究了PtoWOX11/12a在侧根的形成中的功能。通过表达模式分析发现，PtoWOX11/12a具在在中柱鞘中高表达，在弯曲部位表达逐渐减低，并且在侧根原基部位不表达，这表明了PtoWOX11/12a在不定根弯曲中抑制侧根的形成。表型功能分析进一步验证了PtoWOX11/12a到负调控侧根的形成，解剖学也表明了综合PtoWOX11/12a抑制侧根建成细胞向侧根原基转变。转录组和共表达网络分析表明了PtoWOX11/12a可能通过调控茉莉酸信号负调控侧根的形成。.总之，本研究阐明了PtoWOX11/12a调控不定根向地生长的生物学机理，并且进一步阐明了不定根弯曲生长时对侧根形成的影响。向地弯曲生长和侧根生长是植物根系生长的两个方面，对其协调机制的阐明具有重要的理论价值和实践意义。