阿拉伯芥中溫度差異性反應

目前對於植物如何克服不同溫度逆境，維持其生長或生存的機制尚不清楚。先前的研究發現，阿拉伯芥中HSA32受熱誘導表現的溫度區間與其他熱休克蛋白質（HSPs）如HSP101不同。在處理時間均維持1小時的條件下，32°C誘導HSA32蛋白質的表現量為最高，而HSP101蛋白質最高表現量則出現在35°C到37°C之間。本研究試圖找出此溫度差異性反應的調控機制。定量RT-PCR分析顯示HSA32基因表現量在32°C時比其在37°C時高，而HSP101正好相反。Nuclear run-on實驗證明此差異性的調控發生在轉錄層次上。阿拉伯芥HSFA1的四個成員在此反應扮演的角色也有所不同。HSFA1a單獨存在時便足以引發HSA32及HSP101的溫度差異性反應，但若只有HSFA1b或HSFA1d存在時，其辨別不同溫度的能力則會消失。此外，我們也發現HSA32的啟動子區域足以引發熱誘導反應，但卻不足以啟動溫度差異性反應。進一步實驗結果暗示HSA32的內含子或蛋白質編碼區域可能參與了溫度差異性反應的調控。利用微陣列技術分析基因表現量後發現有269和226個基因分別對於32°C和37°C有偏好性。利用32°C/ 37°C溫度轉換測試基因表現的反應，可發現兩種主要反應模式：初始溫度相關和初始溫度不相關。對於HSA32而言，其基因表現量在32°C /37°C組別中與在只處理32°C中類似，反之亦然。對於HSP101則是其基因表現量在32°C /37°C和37°C /32°C的組別中為處理32°C和37°C組別中的平均值。總體而言，此研究幫助我們瞭解植物面對不同溫度逆境時會如何採取應對方式。

關鍵字

阿拉伯芥；溫度差異性反應

並列摘要

How plants respond to different degrees of high temperature is not clear. We previously observed that in Arabidopsis HSA32 and other heat shock proteins (HSPs) were induced by different optimal temperatures. HSA32 protein level was highest after heat treatment at 32°C in seedlings, while most other HSPs such as HSP101 reached highest level at 35°C to 37°C. In this study, we tried to elucidate the mechanism underlying the differential temperature response (DTR). The heat-induced transcript level of HSA32 was higher at 32°C than that at 37°C, while transcript level of HSP101 was opposite. Four members of A1-type heat shock factors (HSFA1s) in Arabidopsis played different roles in this response. HSFA1a alone was sufficient in conferring DTR, whereas HSFA1b or HSFA1d alone was insufficient in discriminating the temperature difference. Our data also suggested that the promoter region of HSA32 is insufficient in driving the DTR of a reporter gene. From nuclear run-on assay, we confirmed that DTR was caused by newly synthesized RNA and was regulated at transcriptional level. Furthermore, microarray analysis of transcriptomes at 22°C, 32°C or 37oC showed genes displayed DTR, with 269 and 226 genes favorably induced at 32°C and 37°C, respectively. Sequential heat treatment first at 32°C then shifted to 37°C or vice versa revealed two modes of heat stress response: initial temperature-dependent or independent. Taken together, we provide a new aspect for how plants react while they facing to different temperatures.

並列關鍵字

Arabidopsis thaliana ； differential temperature response

參考文獻

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阿拉伯芥中溫度差異性反應

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