華中農(nóng)業(yè)大學學者揭示乙烯-茉莉酸互作介導水稻根系響應鹽脅迫的調(diào)控機制

　　近日，華中農(nóng)業(yè)大學植物科學技術學院尹昌喜課題組揭示了乙烯-茉莉酸互作介導水稻根系響應鹽脅迫的調(diào)控機制。

 

　　鹽脅迫是限制全球糧食作物生產(chǎn)的主要非生物脅迫之一。據(jù)統(tǒng)計，全世界約有9.3億hm2的土地遭受鹽漬化，約20%的灌溉土地受到鹽漬化影響，其中我國的土壤鹽漬化面積大約有3600萬hm2，嚴重限制著我國糧食生產(chǎn)。水稻（Oryza sativa L.）是世界上最重要的糧食作物之一，全球約有一半人口以稻米作為主糧。然而，鹽脅迫會造成水稻生長發(fā)育受阻，最終導致水稻減產(chǎn)。因此，探究水稻耐鹽機制，有望為培育耐鹽水稻品種、提高鹽漬化土地的水稻產(chǎn)量提供理論依據(jù)和實踐指導，進而保障我國乃至全球的糧食安全。植物激素乙烯（ETH）和茉莉酸（JA）被稱為逆境激素，它們參與調(diào)控植物響應多種逆境。然而，ETH與JA互作調(diào)控水稻種子根響應鹽脅迫的分子機制尚不清楚。

 

 

　　該研究發(fā)現(xiàn)，鹽脅迫通過上調(diào)ETH生物合成基因OsSAMS、OsACS和OsACO的轉(zhuǎn)錄來促進ETH生物合成；然而，鹽脅迫誘導的乙烯不能直接抑制水稻種子根生長，而是通過促進JA的生物合成間接地抑制水稻種子根的生長。此外，鹽脅迫還可以通過ETH非依賴途徑促進JA的生物合成，進而抑制水稻種子根的生長（圖1）。進一步研究發(fā)現(xiàn)，鹽脅迫誘導的JA通過下調(diào)OsPLT和細胞分裂相關基因的轉(zhuǎn)錄來抑制根分生組織細胞的增殖，鹽脅迫誘導的JA還能通過下調(diào)OsXTH和OsEXP的轉(zhuǎn)錄來抑制根細胞的伸長，從而抑制水稻種子根的生長（圖1）。

 

　　圖2. JA通過介導根細胞增殖和細胞伸長調(diào)控水稻種子根生長

 

　　此外，通過比較JA缺失突變體cpm2與其相應野生型水稻的種子根在響應鹽脅迫方面的差異，證實了JA能夠調(diào)控水稻耐鹽性（圖2）。這意味著通過分子標記輔助選擇技術、轉(zhuǎn)基因與基因編輯等技術調(diào)控JA代謝或信號有望增強水稻耐鹽性。該研究成果為培育耐鹽水稻品種、提高鹽漬化土地的水稻產(chǎn)量提供了理論依據(jù)。可見，該研究成果具有廣闊的應用前景。

 

　　The phytohormones ethylene and jasmonate play important roles in the adaption of rice plants to salt stress. However, the molecular interactions between ethylene and jasmonate on rice seminal root growth under salt stress is unknown. In this study, effects of NaCl on the homeostasis of ethylene and jasmonate and on the rice seminal root growth were investigated. Our results indicate that NaCl treatment promotes ethylene biosynthesis by up-regulating transcription of ethylene biosynthesis genes, whereas NaCl-induced ethylene cannot inhibit rice seminal root growth directly, but rather inhibits growth indirectly by promoting jasmonate biosynthesis. NaCl treatment also promotes jasmonate biosynthesis through an ethylene-independent pathway. Moreover, the analysis results of quantitative real-time PCR and confocal microscopy demonstrate that NaCl-induced jasmonate restricts root meristem cell proliferation by reducing meristem cell number and cell division activity via down-regulated transcription of OsPLT and cell division-related genes, respectively. Additionally, NaCl-induced jasmonate inhibits root cell elongation by down-regulating transcription of cell elongation-related genes, which in turn inhibits seminal root growth. Overall, salt stress promotes jasmonate biosynthesis through ethylene-dependent and -independent pathways in the rice seminal root, and salt-induced jasmonate inhibits the rice seminal root growth by inhibiting root meristem cell proliferation and root cell elongation under salt stress.

 

　　論文鏈接：https://doi.org/10.1093/jxb/erab206