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標題: | 光週期與養分限制對俄氏草成花反轉及時期轉換的效應與ToFT genes參與角色 Effects of photoperiod, resource limitation and the role of ToFT genes on floral reversion and phase transition in Titanotrichum oldhamii |
作者: | Hsin-Yi Huang 黃馨儀 |
指導教授: | 王俊能(Chun-Neng Wang) |
共同指導教授: | 鄭石通(Shih-Tong Jeng) |
關鍵字: | 俄氏草,珠芽,成花反轉,時期轉換,光週期,碳素資源,FLOWERING LOCUS T, Titanotrichum oldhamii,bulbils,floral reversion,phase transiton,photoperiod,carbon resource,FLOWERING LOCUS T, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 營養期至繁殖期之時期轉換受嚴密的調控,環境訊息為其中一個重要的因子。俄氏草為兼行有性生殖與無性生殖的珠芽植物,夏季時開花(有性生殖),秋季日照縮短時,其花序頂端之原基會反轉成珠芽序(變形花序),而原本花序上的花原基逆轉為由珠芽(無性生殖)組成的珠芽叢構造,稱為成花反轉。此外,俄氏草在原生環境條件中,若該個體生長於陰暗或是養分不充足條件下,俄氏草植株發育成熟進入繁殖時期,植株將不經歷有性生殖開花,莖頂將直接轉換發育為珠芽序。故弱光可能會誘導成花反轉。為了調查弱光(醣類受限)條件下是否促使成花反轉發生,進入繁殖期植物以正常光照(100 至 150 μmol m-2s-1)和弱光(5 至15 μmol m-2s-1)處理做為比較。弱光處理將造成花朵敗育,產生的敗育花可視為成花反轉之過渡產物。另外,持續正常光處理組別之花序最終仍發生成花反轉,也暗示著醣類限制可能會促使成花反轉。再者,進一步測量俄氏草花序發育時期醣含量較與珠芽時期為高。因此,藉由遮光處理模擬醣限制情況加以驗證。將第一朵花開時期之植株遮光90%葉面積(S90),並記錄花序上節位狀態至轉換發育珠芽序時期以評估資源限制的效應。於S90個體約10.5天達百分之五十開花,早於未遮光之對照組的13天。並且S90組於轉換發育珠芽期前約有25朵花(67個節位)較對照組32朵花(74個節位)少。這些結果支持在藉由遮光處理導致的醣限制條件下,花期受到限制而增加轉換珠芽發育的可能性。
另一方面,為了調查光週期對俄氏草時期轉換的效應,自珠芽開始分別培養於長日照(LDs, 8D: 16L)或短日照條件(SDs, 16D: 8L),其中短日照植株進入繁殖期時將不發育花而直接轉換發育珠芽,而長日照條件下將誘導更多花發育。因此,光週期調控俄氏草繁殖時期之時期轉換。FLOWERING LOCUS T (FT)是匯整光週期訊息調控開花重要因子,而俄氏草之FT同源基因可能與成花反轉或珠芽發育現象具關連性。俄氏草的2條ToFT genes皆受光週期調控,於長日照條件表現呈週期震盪(光照後16 hr時間點表現量較4hr高),短日照下兩個時間點(光照後0 hr和8 hr兩個時間點)表現量差異較長日照小。此外,ToFT genes皆於轉換珠芽時期大量表現,且ToFT1於莖頂表現量較ToFT2高。藉由將俄氏草ToFT genes至阿拉伯芥全株過量表現,皆顯示2條ToFT genes為提早開花之性狀,顯示其功能保守性。僅管2條ToFT genes為功能性重覆,但已逐漸出現分化情形。 The transition from vegetative to reproductive phase was strictly regulated: environmental signal is one of the important factors. Titanotrichum oldhamii utilizes a mixed sexual and asexual reproductive strategy, which is flowering in summer and generating bulbils to replace flowers on inflorescences, which called floral reversion, when day length shortens. In addition, it generates bulbils directly under weak light or nutritional inadequacy condition. To investigate whether light intensity and carbohydrate limitation condition promote floral reversion, pre-flowering plants were treated with normal (100 to 150 μmol m-2s-1) and weak (5 to 15 μmol m-2s-1) light intensity respectively. The weak light treatment led to aborted flowers, an intermediate form of floral reversion in T. oldhamii. Besides, the continuous normal light treatment ones, which inflorescence apex eventually transit to bulbil development. Moreover, the sugar content of transit to bulbil stage is lower than inflorescences stage. Those implies carbohydrate limitation might restrict flowering and trigger reversion to bulbils. Shading trial was proposed to mimic a carbohydrate limitation condition. Plants bloomed on the first day were shaded 90% leaf area and were recorded number of flower on inflorescence nodes generated before reversion to bulbils. Day to 50% flowering for shaded individuals (around 10.5 days) was earlier than non-shaded ones (around 13 days) and also number of fully developed flowers is less on shaded individuals (about 25 flowers from 67 nodes) before reversion compared to non-shaded control (about 32 flowers from 74 nodes). This supported that carbohydrate limitation restricts flowering and increases possibility of transition to bulbils. On the other hands, to investigate the effect of photoperiod on developmental switches of inflorescence transition, seedlings were grown under long days (LDs, 8D: 16L) or short days (SDs, 16D: 8L) photoperiod. SDs induced the inflorescence of plants transiting to bulbiliferous shoots directly without normal flowers, in contrast, LDs induced more flowers. FLOWERING LOCUS T (FT), a pivotal flowering pathway integrator for photoperiod signals, could possibly be involved in floral reversion to bulbils. Two ToFT genes are photoperiod-dependent with circadian oscillation expressed in LDs (expression levels are higher at 16 hr than 4hr after dawn), but the pattern is unclear in SDs (compare 0 hr and 8 hr after dawn). Moreover, ToFT genes had higher expression during transition stage to bulbil, and also ToFT1 epxerssion is higher than ToFT2 at apex in this period. In addition, functional studies via ectopically expressing ToFT genes in Arabidopsis can promote early flowering phenotype, which reveals a conserve function of two ToFT genes. Although two ToFT genes would be functional redundant, they might have sub-functionalization. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/59655 |
DOI: | 10.6342/NTU201700635 |
全文授權: | 有償授權 |
顯示於系所單位: | 植物科學研究所 |
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