在溫帶、亞熱帶，以及高海拔地區的早春時期，水稻幼苗對於低溫特別敏感，因此改善水稻的耐寒能力將有助於增加稻米的產量。之前研究已知，水稻內屬於1RMYB的MYBS3轉錄因子會調控糖的訊息傳遞;目前的研究發現，MYBS3在水稻內，對於低溫環境的適應，扮演重要的角色。經由MYBS3蛋白質功能的增加與喪失研究發現， MYBS3對於增加水稻的耐寒能力，扮演著充份與必要條件的角色。持續表現MYBS3蛋白的轉殖水稻，可抵抗4℃環境至少一個星期，而且在正常環境下的田裡種殖，並不影響其產量。經由微矩陣基因晶片技術，研究MYBS3蛋白質功能增加與喪失的轉殖水稻之轉錄基因圖樣，將有助於確認許多參與MYBS3調控冷訊息傳遞的其他基因。在低溫環境下，受MYBS3活化的基因，已被證實會參與水稻及其他植物的各種不同的非生物性逆境反應。然而，在我們的研究發現，水稻於低溫環境下，MYBS3在轉錄層次上，會抑制DREB1/CBF所調控的冷訊息傳遞。當低溫來臨時，DREB1基因會快速且短暫的表現，然而MYBS3則是表現於後期；由此顯示，水稻內具有兩條訊息傳遞路線，以提供水稻適應長短期的低溫逆境。因此，我們的研究發現了水稻內，另一條調控適應低溫環境的新途徑。

Rice seedlings are particularly sensitive to chilling in early spring in temperate and subtropical zones and in high elevation areas. Improvement of chilling tolerance in rice may significantly increase rice production. MYBS3 is a single DNA-binding repeat (1R) MYB transcription factor previously shown to mediate sugar signaling in rice. In the present study, we observed that MYBS3 also plays a critical role in cold adaptation in rice. Gain- and loss-of-function analyses indicated that MYBS3 was sufficient and necessary for enhancing cold tolerance in rice. Transgenic rice constitutively over-expressing MYBS3 tolerated 4°C for at least 1 week, and exhibited no yield penalty in normal field conditions. Transcription profiling of transgenic rice over- or under-expressing MYBS3 led to identification of many genes in the MYBS3-mediated cold signaling pathway. Several genes activated by MYBS3 as well as inducible by cold have previously been implicated in various abiotic stress response and/or tolerance in rice and other plant species. Surprisingly, MYBS3 repressed the well-known DREB1/CBF-dependent cold signaling pathway in rice, and the repression appears to act at the transcriptional level. DREB1 responded quickly and transiently while MYBS3 responded slowly to cold stress, which suggests distinct pathways act sequentially and complementarily for adapting short- and long-term cold stress in rice. Our studies thus reveal a hitherto undiscovered novel pathway which controls cold adaptation in rice.

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