同源基因OsbHLH068和AtbHLH112參與阿拉伯芥鹽逆境耐受性及調控開花之研究

Studies of Homologous Genes, OsbHLH068 and AtbHLH112, on Salt Tolerance and Flowering Regulation in Arabidopsis

謝謙謙(Cian-Cian Hsieh)

指導教授 ： 張孟基

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601161

摘要

basic/Helix-Loop-Helix (bHLH) 為第二大的植物轉錄因子家族，參與調控植物的發育和生理作用。公開的微陣列數據顯示OsbHLH068受乾旱和鹽逆境誘導表現。由於OsbHLH068在調節水稻非生物逆境反應和生長發育下所扮演的角色仍然所知甚少，本研究主要探討OsbHLH068及其同源基因AtbHLH112的功能。組織化學GUS染色顯示，從營養生長期到生殖生長期的轉變過程中，OsbHLH068和AtbHLH112的表現部位有高度的相似性。此外，OsbHLH068的轉錄表現受黑暗所抑制。異質過量表現OsbHLH068在阿拉伯芥中會延遲種子發芽和促進根的伸長。然而AtbHLH112降低表現的突變植株則加速種子發芽，而對根的伸長沒有影響。在生殖生長期，異質過量表現OsbHLH068的阿拉伯芥和AtbHLH112降低表現的突變株皆顯示延遲開花的特性。此外，由遺傳互補實驗顯示，以內生AtbHLH112起動子驅動位於細胞核的GFP-OsbHLH068或OsbHLH068-GFP蛋白的表現，雖可恢復萌芽之缺陷，但卻使原先Atbhlh112突變體的開花更加延遲。另外，DNA微陣列和qPCR數據顯示，開花基因SOC1和FT在異質過量表現OsbHLH068的阿拉伯芥中表現量下降。而GA20ox1及GA3ox1表現量則上升，表示轉殖阿拉伯芥延遲開花可能是由於改變吉貝素代謝或合成的結果。以上數據說明OsbHLH068和AtbHLH112雖然同為F亞科中的同源基因，且在植物耐鹽逆境下扮演相似的角色，但在開花時間上的調控有著相反作用，此現象可能來自趨異演化的結果，並顯示bHLH可能在單雙子葉植物中扮演不同角色。

關鍵字

轉錄因子 ； bHLH ； 鹽逆境 ； 開花

並列摘要

The second largest transcription factor (TF) family, basic/Helix-Loop-Helix (bHLH), plays a regulatory role in plant developmental and physiological processes.Analysis of publicly available microarray data revealed that the expression ofOsbHLH068 was up-regulated under both drought and salt stress conditions. However,the roles of OsbHLH068 in regulating rice abiotic stress response and developmentalprocess remain poorly known. Therefore, in this study, we aimed to characterize theregulatory roles of OsbHLH068 and its homolog, AtbHLH112. Histochemical GUSstaining indicated that the spatiotemporal expression of OsbHLH068 was highly similar to that of AtbHLH112 during the juvenile-to- adult phase transition. Besides, the
transcriptional expression of OsbHLH068 was reduced under darkness conditions. Heterologous over-expression of OsbHLH068 in Arabidopsis delayed seed germinationand increased root elongation, while down-expression of AtbHLH112 in mutant accelerated seed germination but displayed no effects on root elongation. At reproductive stage, both the OsbHLH068-overexpessed transgenic Arabidopsis and Atbhlh112 mutant displayed a late-flowering phenotype. Moreover, complementary expression of OsbHLH068-GFP driven by an AtbHLH112 promoter could restore the germination deficiency of Atbhlh112 mutant but caused more severe delay flowering. Microarray and qPCR data revealed that the expressions of SOC1 and FT were down-regulated in OsbHLH068-overexpessed Arabidopsis. Interestingly, the expression of GA20ox1 and GA3ox1 were up-regulated, which indicated that the delay of flowering time in heterologous OsbHLH068 overexpression transgenic Arabidopsis maybe due to the alteration of GA biosynthesis or metabolism. Taken together, these data illustrate that OsbHLH068 and AtbHLH112, two homologs in F subfamily, play a similar role in plant response to salt stress but act oppositely in controlling flowering time, and which may result from divergent evolution. In other word, OsbHLH068 and AtbHLH112 may function differently either in rice or Arabidopsis.

並列關鍵字

Transcription factor ； OsbHLH068 ； AtbHLH112 ； Salt stress ； Flowering

參考文獻

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