近日，華中農業大學園藝植物生物學教育部重點實驗室劉繼紅教授團隊研究成果以“CHH methylation of genes associated with fatty acid and JA biosynthesis contributes to cold tolerance in autotetraploids of Poncirus trifoliata”為題的研究論文在Journal of Integrative Plant Biology發表，該研究從DNA甲基化和轉錄水平上揭示了柑橘多倍體抗寒的分子調控機制。   　　柑橘是世界第一大水果，也是我國南方最重要的水果，但柑橘產業受到多種非生物逆境的制約。因此，研究柑橘資源非生物逆境應答的分子調控機制具有重要理論意義和潛在應用價值。枳（Poncirus trifoliata （L.） Raf. ）是柑橘上最常用的砧木，抗寒性較強，是研究低溫應答的重要柑橘資源。已有研究表明，相對二倍體來說，四倍體常常具有更好的遺傳適應性和抗逆性。植物全基因組加倍往往會引起表觀遺傳和轉錄水平的改變，但是這些變化如何調控多倍體抗性尚不清楚。   　　課題組前期通過自然群體篩選獲得了一批枳同源四倍體資源，抗性評價表明，枳四倍體植株比二倍體更抗寒。對低溫處理前后的二倍體和四倍體植株進行了轉錄組和全基因組甲基化測序，結果表明在低溫處理后，二倍體和四倍體均發生了全基因組去甲基化，但四倍體甲基化水平下降更大，低溫脅迫相關基因更大程度地被激活。轉錄組和甲基化組聯合分析表明，低溫條件下，多個不飽和脂肪酸和茉莉酸合成通路的關鍵基因（如FAD和LOX）在四倍體中都顯著高表達，并且這些基因的上游或者下游區域CHH甲基化在四倍體和二倍體之間存在差異。代謝和生理測定表明，四倍體在低溫脅迫下積累了更多的不飽和脂肪酸和茉莉酸。本研究首次解析了多倍體柑橘抗寒性增強的表觀遺傳機制，為多倍體枳的應用提供了重要理論基礎，也為多倍體植物抗逆機理研究提供了重要參考。   　　華中農業大學園藝林學學院在讀博士研究生王月為該論文第一作者，劉繼紅教授為通訊作者。我校畢業碩士生左蘭蘭和李春龍教授也參與了該研究。本研究受到國家重點研發計劃項目和國家自然科學基金資助。   　　[英文摘要]   　　Polyploids have elevated stress tolerance, but the underlying mechanisms remain largely elusive. In this study, we showed that naturally occurring tetraploid plants of trifoliate orange （Poncirus trifoliata （L.） Raf.） exhibited enhanced cold tolerance relative to their diploid progenitors. Transcriptome analysis revealed that whole-genome duplication was associated with higher expression levels of a range of well-characterized cold stress-responsive genes. Global DNA methylation profiling demonstrated that the tetraploids underwent more extensive DNA demethylation in comparison with the diploids under cold stress. CHH methylation in the promoters was associated with up-regulation of related genes, whereas CG, CHG and CHH methylation in the 3'-regions was relevant to gene down-regulation. Of note, genes involved in unsaturated fatty acids （UFAs） and JA biosynthesis in the tetraploids displayed different CHH methylation in the gene flanking regions and were prominently up-regulated, consistent with greater accumulation of UFAs and JA when exposed to the cold stress. Collectively, our findings explored the difference in cold stress response between diploids and tetraploids at both transcriptional and epigenetic levels, and gained new insight into the molecular mechanisms underlying enhanced cold tolerance of the tetraploid. These results contribute to uncovering a novel regulatory role of DNA methylation in better cold tolerance of polyploids.   　　原文鏈接：https://www.jipb.net/EN/10.1111/jipb.13379