苦瓜花性之轉錄體分析

Abstract

苦瓜 (Mormordica charantia L.) 為雌雄同株異花 (monoecious) 作物，外施激勃素 (gibberellin, GA) 可誘導其雌花生成，有別於其他葫蘆科 (Cucurbitaceae) 作物。次世代定序 (next generation sequencing, NGS) 不需序列資訊等，有利於非模式物種 (non-model organism) 之轉錄體 (transcriptome) 定序。外施GA3於苦瓜品種‘月華’六至八葉期苗株，會使花性雄雌比由37降至23，促進雌花生成。經萃取激勃素處理苦瓜苗株之總RNA，以次世代定序技術進行轉錄體分析，組成106,057 條contigs，其中40,854條可被註解 (annotate) 為推定基因 (putative gene)，其中8,948個開放解讀框架 (open reading frame) 註解的基因於處理組與對照組中表現量差異達兩倍以上。次世代定序結果顯示，外施激勃素會使苦瓜中激勃素生合成相關基因表現量下降；激勃素受體基因McGID1s、激勃素訊息傳遞基因McXERICOs、乙烯訊息傳遞基因McEIN3/EILs及茉莉酸 (jasmonic acid, JA) 生合成基因McLOX1表現量上升；McDELLAs、ARF6s及ARF8s等基因表現量下降，其中雄蕊 (stamen) 發育相關基因McMYB24.1於激勃素處理表現量較低，可能抑制雄蕊發育；而McXERICOs之表現量增加可能促進離層酸之生合成以改變花性。外施激勃素使ARF6s及ARF8s表現量降低，造成茉莉酸之生合成下降進而抑制McMYB24表現，抑制雄蕊發育；外施激勃素可能藉由誘導McXERICOs之表現進而促進離層酸生合成關鍵基因McNCEDs之表現而累積離層酸，並誘導乙烯生合成共同促進植株雌性化。

Bitter gourd (Momordica charantia L.) is one of monoecious species belonging to the family Cucurbitaceae. Unlike other Cucurbitaceae crops, gibberellin (GA) promotes female flower formation in bitter gourd. Next generation sequencing (NGS) provides a platform to analyze transcriptome for non-model organisms. Application of 100 mg·L-1 GA3 on seedlings of bitter gourd ‘Moon Light’ at 6~8-leaf stage reduced the ratio of male to female flower from 37 to 23. RNA isolated from GA-treated bitter gourd was conducted for comparative transcriptome analysis using NGS technology. 40,854 among 106,057 contigs were annotated as putative genes. Approximately 8,948 open reading frame-annotated genes showed a 2-fold differential expression between RNA of control and treatment. Gene expression of McGIDs, McXERICOs, McEIN3/EILs, and McLOX1s were up-regulated and that of McDELLA, McARF6s, and McARF8s were down-regulated after GA treatment. McMYB24.1 showed down regulated following GA application and it might play the role in inhibition of stamen development. Up regulation of McXERIOs might play a crucial role in GA-induced femaleness by promoted ABA accumulation in bitter gourds. McARF6s, and McARF8s were down-regulated after GA application which caused the reduction of jasmonate biosynthesis and repressed the expression level of McMYB24. These might inhibit the stamen development. McXERIOs might be induced following GA treatment which promoted the expression of McNCEDs and ABA accumulation. It also induced thylene biosynthesis in bitter gourds following GA application. These might promote the femaleness level of bitter gourd together.