The Plant Cell:餘迪求等擬南芥WRKY57轉錄因子研究獲進展

植物葉片衰老受到多種發育因子和環境因子所調控。外源植物激素茉莉酸（JA）處理可以誘導葉片細胞迅速進入衰老程序，而生長素（Auxin）卻可以有效地抑制該過程發生。眾所周知，植物激素JA和auixn介導的信號途徑之間存在著交叉調控通路，並在植物發育和抵抗病原菌侵染等生理過程中發揮著重要調控功能。但是JA和auixn在植物葉片衰老過程中的交叉調控機制及其信號通路，目前尚不了解。

中科院西雙版納熱帶植物園植物分子生物學組組長餘迪求研究員指導的青年研究骨幹姜豔娟博士研究發現，擬南芥WRKY57轉錄因子參與調控了植物激素JA和auixn所介導的植物葉片衰老信號途徑之間的交叉調控通路，並發揮重要的調控功能。WRKY57基因的表達分析表明，WRKY57基因顯著受JA誘導表達，並在衰老葉片中具有較高的表達水平。JA處理3天和5天後，兩個wrky57基因突變體表現出典型的衰老表型，即葉片嚴重黃化、葉片內葉綠素含量減低和葉片具有更高的細胞死亡速率。進一步研究表明，一些衰老相關基因（特別是SAG12和SEN4基因）的表達量在wrky57基因突變體內顯著增強。染色質免疫共沉澱實驗證實WRKY57蛋白可以直接結合到SAG12和SEN4基因啟動子上，並抑制了它們的轉錄水平。此外，體外和體內實驗均證明，WRKY57蛋白能有效地與JA信號途徑中的抑制子JAZ4/JAZ8和auxin信號途徑中的抑制子IAA29之間發生相互作用。與植物激素JA和auxin在分別調控植物葉片衰老的相反功能一致，JAZ4/8和IAA29在JA誘導的葉片衰老過程中也表現出相反的表型，而且JAZ4/8和IAA29蛋白是通過競爭性方式與WRKY57蛋白發生相互作用。

綜上所述，研究結果說明了植物激素生長素（Auxin）所介導的信號途徑可以通過WRKY57蛋白而拮抗調控茉莉酸（JA）誘導的葉片衰老過程。相關研究以Arabidopsis WRKY57 functions as a node of convergence for Jasmonic acid- and auxin-mediated signaling in Jasmonic acid-induced leaf senescence為題在線發表於國際學術期刊Plant Cell上。該課題得到了國家自然科學基金-青年科學基金項目的資助。  （生物谷Bioon.com）

生物谷推薦的英文摘要：

Plant Cell    doi：10.1105/tpc.113.117838

Arabidopsis WRKY57 Functions as a Node of Convergence for Jasmonic Acid– and Auxin-Mediated Signaling in Jasmonic Acid–Induced Leaf Senescence[W]

Yanjuan Jiang， Gang Liang， Shizhuo Yang and Diqiu Yu1

Leaf senescence is regulated by diverse developmental and environmental factors. Exogenous jasmonic acid (JA) can induce leaf senescence， whereas auxin suppresses this physiological process. Crosstalk between JA and auxin signaling has been well studied， but not during JA-induced leaf senescence. Here， we found that upon methyl jasmonate treatment， Arabidopsis thaliana wrky57 mutants produced typical leaf senescence symptoms， such as yellowing leaves， low chlorophyll content， and high cell death rates. Further investigation suggested that senescence-associated genes were upregulated in the wrky57 mutants. Chromatin immunoprecipitation experiments revealed that WRKY57 directly binds to the promoters of SENESCENCE4 and SENESCENCE-ASSOCIATED GENE12 and represses their transcription. In vivo and in vitro experiments suggested that WRKY57 interacts with JASMONATE ZIM-DOMAIN4/8 (JAZ4/8) and the AUX/IAA protein IAA29， repressors of the JA and auxin signaling pathways， respectively. Consistent with the opposing functions of JA and auxin in JA-induced leaf senescence， JAZ4/8 and IAA29 also displayed opposite functions in JA-induced leaf senescence and competitively interacted with WRKY57. Our results suggested that the JA-induced leaf senescence process can be antagonized by auxin via WRKY57. Moreover， WRKY57 protein levels were downregulated by JA but upregulated by auxin. Therefore， as a repressor in JA-induced leaf senescence， WRKY57 is a common component of the JA- and auxin-mediated signaling pathways.