阿拉柏芥bHLH27和bHLH51基因參與遠紅光及茉莉酸訊息調控幼苗發育之功能性研究

Functional studies of bHLH27 and bHLH51 genes in regulation of seedling development under far-red light and JA signaling in Arabidopsis

黃友慧(You-Huei Huang)

指導教授 ： 謝旭亮

國立臺灣大學/生命科學院/植物科學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902511

摘要

植物透過光以及各種植物賀爾蒙協同感知外界環境變化，以促成生長與適應。在阿拉伯芥中，具有雙重功能的蛋白質FIN219/JAR1，會被遠紅光 (FR)激發並作為將茉莉酸 (JA)轉換成活化態茉莉酸-異白胺酸 (JA-isoleucine)之酵素，參與在茉莉酸訊息傳遞。為更加了解FIN219/JAR1如何調節遠紅光與茉莉酸訊息傳遞，透過微陣列分析(microarray analysis)顯示FIN219調控了許多鹼性螺旋-環-螺旋(basic helix-loop-helix, bHLH)轉錄因子的表現量。在這些被調控的基因之中，bHLH27 與bHLH51被FIN219所正調控。進一步的研究顯示，在低遠紅光、高遠紅光、藍光、紅光、白光與甚至黑暗當中，bHLH27 與bHLH51突變株的幼苗，對於外加的甲基化茉莉酸處理，表現出了與野生型相比顯著性地更低的下胚軸抑制率，顯示出bHLH27與bHLH51參與在光型態發生、暗型態發生與茉莉酸訊息傳遞當中。不僅是地上部的下胚軸延長，地下部的初級根根長的量測結果指出bHLH27與bHLH51突變株具有比野生型更短的根，顯示bHLH27與bHLH51作為初級根發育的正調控者。另外，如同對於茉莉酸抑制下胚軸較不敏感的反應，bHLH27與bHLH51突變株的也表現出了與Col-0相比，對甲基茉莉酸抑制根長現象較不敏感。此外，bHLH27與bHLH51正向調控了種子發育，兩者的突變株也有晚開花的現象。不僅如此，花青素累積、葉綠素含量以及許多茉莉酸反應的標識基因，也都受到bHLH27與bHLH51的突變、以及外加甲基茉莉酸與否的影響。這些證據都顯示，bHLH27與bHLH51參與在茉莉酸訊息傳遞鏈當中。除此之外，bHLH27與bHLH51次細胞定位位於細胞核，並具有彼此形成異型二聚體與同型二聚體的能力，這可能暗示了這兩個蛋白質、可能作為轉錄因子並透過不同結合形式調控不同目標基因。總結而言，bHLH27與bHLH51作為FIN219整合之光與茉莉酸訊息傳遞之下游因子，調控轉錄網絡與生理發育。

關鍵字

bHLH27 ； bHLH51 ； 光型態發生 ； FIN219/JAR1 ； 茉莉酸

並列摘要

Plants integrate light and several phytohormones to monitor environmental changes and accomplish growth for adaptation. In Arabidopsis, a dual function protein FIN219/JAR1 is activated by far-red (FR) light and also participates in the jasmonate (JA) signaling pathway by enzymatically converting JA to an active form JA-isoleucine. To further understand how FIN219/JAR1 mediates FR and JA signaling pathways, a microarray analysis was performed and revealed that FIN219 regulated the expression levels of many basic helix-loop-helix (bHLH) transcription factors. Among those affected genes, bHLH27 and bHLH51 were confirmed to be positively regulated by FIN219. Further studies indicated that hypocotyl length measurement of the seedlings under low FR, high FR, blue, red and white light and also in the dark, with MeJA treatments showed that bHLH27 and bHLH51 mutants exhibited significantly lower inhibition rates of hypocotyl elongation than wild type, suggesting the vital roles of bHLH27 and bHLH51 in photo- and skoto-morphogenesis and JA signaling pathways. In addition to the overground part of hypocotyl elongation, the underground root lengths were also measured. Both bhlh27 and bhlh51 mutants have much shorter root lengths than wild type, which indicates that bHLH27 and bHLH51 positively regulate primary root development. Besides, bhlh27 and bhlh51 displayed significantly lower MeJA-mediated inhibition of root elongation than Col-0, which showed a similar response of both mutants to MeJA-mediated inhibition of hypocotyl elongation. Additionally, bHLH27 and bHLH51 positively regulated seeds germination and both mutants showed a delayed flowering. Moreover, anthocyanin accumulation, chlorophyll content and several JA responsive marker genes, were all affected by bhlh27 and bhlh51 mutants with or without MeJA treatment. These results provide further evidence that bHLH27 and bHLH51 are involved in JA signaling pathways. In addition, bHLH27 and bHLH51 are localized in the nucleus and able to form not only homo- but also hetero-dimers with each other, which implies that they can act as active transcription factors and regulate their target genes in various ways. Taken together, bHLH27 and bHLH51 are important downstream components of FIN219-mediated light and JA signaling pathways in regulation of transcriptional networks and physiological development.

並列關鍵字

bHLH27 ； bHLH51 ； photomorphogenesis ； FIN219/JAR1 ； Jasmonates

參考文獻

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