近日，華中農(nóng)業(yè)大學果蔬園藝作物種質創(chuàng)新與利用全國重點實驗室、華中農(nóng)業(yè)大學園藝林學學院桃課題小組研究成果以“Two interacting ethylene response factors negatively regulate peach resistance to Lasiodiplodia theobromae”為題在Plant Physiology發(fā)表。研究揭示了乙烯響應因子PpERF98和PpERF1相互作用調控桃樹響應流膠病菌侵染的分子機制，為桃樹的抗病分子育種提供了重要的基因資源。
流膠病是桃樹栽培過程中常見的主要病害之一，多發(fā)生于我國長江流域及其以南的高溫高濕地區(qū)。該病主要危害桃樹的主干、主枝等部位，造成組織壞死并伴隨大量膠體外溢，導致樹勢衰弱、果實產(chǎn)量和品質下降，嚴重影響桃的經(jīng)濟價值。葡萄座腔菌科（Botryosphaeriaceae）真菌可可毛色二孢（L. theobromae）是一種強致病力的半活體營養(yǎng)型真菌，是引起桃流膠病的主要致病菌之一，也可引起葡萄和楊樹潰瘍病、蘋果輪紋病以及茶樹葉斑病等。
課題組前期研究結果表明外源乙烯和茉莉酸甲酯增加桃對流膠病菌L. theobromae的敏感性，而水楊酸增加桃的抗性（Zhang et al., 2021, Horticulture Research），但是其分子機制尚不明晰。作者對接種L. theobromae的桃枝條進行轉錄組和基因表達分析，發(fā)現(xiàn)與擬南芥ERF98同源的兩個基因PpERF98-1和PpERF98-2受流膠病菌和外源乙烯處理顯著誘導，且在流膠病敏感的桃品種中轉錄水平更高。為了探究PpERF98在桃應答流膠病菌中的作用和調控網(wǎng)絡，對PpERF98-1/2沉默和過表達桃苗和番茄植株的抗性分析，證實了這兩個轉錄因子負調控桃對L. theobromae的抗性。進一步發(fā)現(xiàn)PpERF98-1和PpERF98-2可以自身形成同源二聚體或相互作用形成異源二聚體，結合到茉莉酸/乙烯信號通路上的關鍵轉錄因子PpERF1的啟動子上并激活其表達；同時PpERF98-1/2也可以與PpERF1蛋白形成異源二聚體共同介導茉莉酸/乙烯信號通路的ERF分支，最終削弱水楊酸依賴的抗病防御反應。本研究揭示了乙烯基于PpERF98-PpERF1轉錄級聯(lián)參與調控桃對L. theobromae易感性的分子機制，為桃的抗病分子育種提供了重要的可編輯基因和靶點。
果蔬園藝作物種質創(chuàng)新與利用全國重點實驗室、我校園藝林學學院博士后張東梅為論文第一作者，劉軍偉副研究員為該論文的通訊作者。華中農(nóng)業(yè)大學李國懷教授和劉繼紅教授、意大利都靈大學Francesca Cardinale教授參與并指導了這項研究工作。本研究得到了國家自然科學基金（32202410和32172516）、國家現(xiàn)代桃產(chǎn)業(yè)技術體系（CARS-30）的經(jīng)費資助。
【英文摘要】
Gummosis is one of the most common and destructive diseases threatening global peach （Prunus persica） production. Our previous studies have revealed that ethylene and methyl-jasmonate enhance peach susceptibility to Lasiodiplodia theobromae, a virulent pathogen inducing gummosis; however, the underlying molecular mechanisms remain obscure. Here, two ethylene response factors, PpERF98 and PpERF1, were identified as negative regulators in peach response to L. theobromae infection. expression of two putative paralogs, PpERF98-1/2, was dramatically induced by ethylene and L. theobromae treatments and accumulated highly in the gummosis-sensitive cultivar. Silencing of PpERF98-1/2 increased salicylic acid （SA） content and pathogenesis-related genes PpPR1 and PpPR2 transcripts, conferring peach resistance to L. theobromae, whereas peach and tomato （Solanum lycopersicum） plants overexpressing either of PpERF98-1/2 showed opposite changes. Also, jasmonic acid markedly accumulated in PpERF98-1/2-silenced plants, but reduction in PpPR3, PpPR4, and PpCHI （Chitinase） transcripts indicated a blocked signaling pathway. PpERF98-1/2 were further demonstrated to directly bind the promoters of two putative paralogous PpERF1 genes and to activate the ERF branch of the jasmonate/ethylene signaling pathway, thus attenuating SA-dependent defenses. The lesion phenotypes of peach seedlings overexpressing PpERF1-1/2 and PpERF98-1/2 were similar. Furthermore, PpERF98-1/2 formed homo-/hetero-dimers and interacted with the two PpERF1 proteins to amplify the jasmonate/ethylene signaling pathway, as larger lesions were observed in peach plants co-overexpressing PpERF98 with PpERF1 relative to individual PpERF98 overexpression. Overall, our work deciphers an important regulatory network of ethylene-mediated peach susceptibility to L. theobromae based on a PpERF98-PpERF1 transcriptional cascade, which could be utilized as a potential target for genetic engineering to augment protection against L. theobromae-mediated diseases in crops and trees.
論文鏈接：https://academic.oup.com/plphys/advance-article/doi/10.1093/plphys/ kiad279/715981 4?searchresult=1
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