利用微生物共生來增強植物的抗病力為目前重要的農業栽培對策，而根際環境為主要與共生菌相互作用的場所，前人研究指出根部液胞膜的糖轉運蛋白 AtSWEET2 透過調節根部細胞中糖平衡控制流向根際的糖，這些糖是微生物附著的關鍵。此外，發現轉錄因子 AtAHL29 會抑制 AtSWEET2 表達。然而在益生菌感染下 AtAHL29 是否参與 AtSWEET2 的調控，值得進一步研究。本研究旨在探討 AtAHL29、AtSWEET2 與商業有益微生物枯草芽孢桿菌（Bacillus subtilis）之間的分子關系。通過阿拉伯芥原生質體瞬時表達，結果顯示，處理 Flg22（來自 B.subtilis 主要感染信號）、賀爾蒙茉莉酸甲酯、離層酸和水楊酸，除了水楊酸之外，都會上調 AtSWEET2 的表現量。然而，AtAHL29 對 AtSWEET2 的抑制並沒有改變。此外，AtAHL29 的 AT hook motif 是其抑制 AtSWEET2 的關鍵。為了證實在植物中 AtAHL29 對 AtSWEET2 的負調控，實驗室獲得 AtAHL29 的功能缺陷突變株（ahl29-6）。與 WT 相比，ahl29-6 突變株中 AtSWEET2 的表達水平在 B.subtilis 感染後顯著升高。同樣，在根部定殖分析中，本研究觀察到 ahl29-6 突變株根部B.subtilis 定殖量顯著減少。綜合以上結果，本研究提出 AtAHL29 負調控 AtSWEET2 表達增加糖分泌，以促進根系和有益微生物之間的相互作用。

Application of beneficial microbial symbiosis is an important strategy to enhance pathogen resistance for agricultural cultivation. Previous studies indicate root-expressed vacuolar sugar transporter AtSWEET2 can regulate sugar homeostasis in cells to titrate secreted sugars that are the key for the attachment of microorganisms, both pathogenic and beneficial microbes. In addition, the transcription factor AtAHL29 was identified to be a repressor to inhibit AtSWEET2 expression. Whether AtAHL29 is involved in regulate AtSWEET2 expression under infection of a beneficial microbe deserves further investigation. In this study, we intend to address the molecular relationship between AtAHL29, AtSWEET2 and the Bacillus subtilis, a commercial beneficial microbe. By using transient expression in Arabidopsis protoplasts, our results showed that the expression of AtSWEET2 was increased with treatments of Flg22 (the major infection signal from Bacillus) and hormone MJ (methyl jasmonate), ABA (abscisic acid), but not SA (salicylic acid). However, overexpression of AtAHL29 constantly inhibited AtSWEET2 expression in all cases. In addition, the AT hook motif of AtAHL29 was crucial to its inhibition of AtSWEET2. And AtSWEET2 transcriptional activity was significantly decreased when 100bp of the upstream of the AtSWEET2 promoter was deleted. To confirm the molecular regulation of AtAHL29 on AtSWEET2 expression in vivo, the functional defective mutant of AtAHL29 (ahl29-6) was obtained. Compared to WT, the expression level of AtSWEET2 in the ahl29-6 mutant was significantly increased in response to Bacillus subtilis infection. Consistently, in the colonization analysis, we observed that roots of ahl29-6 mutant had significantly fewer colonization of Bacillus subtilis. Based on all these results, we propose that AtAHL29 negatively regulates AtSWEET2 expression to increase sugar efflux in order to promote the interaction between roots and beneficial microbes.

蔣宇軒，探討SWEET糖轉運蛋白對植物與枯草感菌共生的影響，國立成功大學生物科技與產業科學系碩士學位論文，2019。

詹雅棻，探討阿拉伯芥SWEET2糖轉運蛋白的分子調控機制，國立成功大學熱帶植物科學研究所碩士學位論文，2018。

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