Nature plant：醋能幫助作物抗旱

近日，日本Riken中心可持續資源科學（CSRS）的研究人員在國際著名植物雜誌Nature plant在線發表題為"Acetate-mediated novel survival strategy against drought in plants"研究論文, 揭示了一個重要的乾旱響應網路，即植物能通過控制糖酵解轉化為乙酸合成途徑開關，調控下游茉莉酸（JA）信號通路，賦予植物乾旱能力。

文章作者通過遺傳篩選方法，篩選到具有較強的抗旱能力的擬南芥突變體hda6。hda6突變體植物在充分澆水的條件下表現出與野生型植物相似的生長。而在乾旱脅迫下，hda6mutants顯示出增強的耐旱性。為了弄清抗旱的原因，文章作者通過分析了乾旱脅迫下hda6全基因表達pattern，發現在乾旱脅迫下，野生型植物中醋酸鹽生物合成途徑被上調，並且在hda6突變體中顯著上調。同時，該小組通過在乾旱條件下,並用乙酸,其它有機酸,或水處理生長正常植物驗證了這個假說。他們發現,用乙酸處理植物14天後超過70%的擬南芥植物都能活性下來，而非乙酸組的植物幾乎全部死亡。如圖Fig1所示。

Fig.1. Acetic Acid Improves Drought Tolerance

The effect of several organic acids on plant drought tolerance after 14 days. From left to right, water, HCl, formic acid, acetic acid, butyric acid, lactic acid, citric acid. Note, only plants treated with acetic acid survived.

為了了解HDA6是如何發揮抗旱機制。遺傳和表達分析表明，HDA6可以抑制PDC1 （編碼丙酮酸脫羧酶基因）和ALDH2B7（編碼乙醛脫氫酶基因）的表達。生化研究表明，HDA6可以結合PDC1和 ALDH2B7基因區域，促進乙酸的生物合成。而且文章提出HDA6是作為乙酸合成途徑開關，正常情況，HDA6可以抑制乙酸生物合成通路，而一旦乾旱條件下，該途徑又被激活，從而增強植物抗乾旱能力（圖Fig.4）。因此，適量的乙酸增加是植物抗旱所必須的。

Fig.2. Quantified survival rate corresponding to the image in Figure 1

目前，雖然轉基因技術可以用來創建更耐旱的植物，但是轉基因作物由於法律法規的限制，並沒有在所有國家推廣，因此，利用醋酸提高植物的耐旱性的一旦被利用，不失為有用，簡單，更便宜的方式。

Fig.3. Aceticacid confers drought tolerance on maize, rice, wheat and rapeseed plants.

Fig.4. Proposed mechanism for acetic acid-induced drought tolerance

Abstract:

Water deficit caused by global climate changes seriously endangers the survival of organisms and crop productivity, and increases environmental deterioration1,2. Plants resistance to drought involves global reprogramming of transcription, cellular metabolism, hormone signalling and chromatin modification3,4,5,6,7,8. However, how these regulatory responses are coordinated via the various pathways, and the underlying mechanisms, are largely unknown. Herein, we report an essential drought-responsive network in which plants trigger a dynamic metabolic flux conversion from glycolysis into acetate synthesis to stimulate the jasmonate (JA) signalling pathway to confer drought tolerance. In Arabidopsis, the ON/OFF switching of this whole network is directly dependent on histone deacetylase HDA6. In addition, exogenous acetic acid promotes de novo JA synthesis and enrichment of histone H4 acetylation, which influences the priming of the JA signalling pathway for plant drought tolerance. This novel acetate function is evolutionarily conserved as a survival strategy against environmental changes in plants. Furthermore, the external application of acetic acid successfully enhanced the drought tolerance in Arabidopsis, rapeseed, maize, rice and wheat plants. Our findings highlight a radically new survival strategy that exploits an epigenetic switch of metabolic flux conversion and hormone signalling by which plants adapt to drought.

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