2009-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/682922摘要：水稻上位葉的葉鞘會於抽穗前開始大量累積澱粉，並於抽穗後快速分解做為提供穀粒充實所需之碳源。在抽穗前累積於葉鞘之澱粉含量與最終穀粒產量成絕對正相關，而此澱粉代謝產物 (例如:蔗糖) 於抽穗後轉運至充實中的穀粒之效率將直接影響穀粒之充實度及充實期長短，故水稻葉鞘中蔗糖於生殖生長期之轉運速率為影響水稻產量及稻米品質的重要因子之ㄧ。並且在環境逆境時，葉鞘暫存性醣類之生理功能則更顯重要，其可擔任補充光合作用同化物 (photoassimilate)不足之緩衝物質 (buffer)，以減少環境逆境對穀粒發育所產生之負面壓力。因此，如能改良水稻生殖生長期碳水化合物由葉鞘轉運至穀粒之效率，將可降低環境逆境對產量及穀粒品質之影響。然而，目前對於水稻葉鞘中調控醣類轉運之機制卻仍不了解。由於蔗糖轉運蛋白 (sucrose transporter; SUT) 為負責將蔗糖轉運至韌皮部，以進行長距離運送之主要蛋白分子，且由本實驗室先前之研究結果顯示，水稻之OsSUT1及OsSUT4基因在葉鞘中之表現會於生殖生長期大量表現，推測此其為主要負責蔗糖運輸之轉運蛋白。因此，本計畫將藉由分析OsSUT1, 4 基因表現之調控機制，探討水稻葉鞘中醣類轉運之調控機制，並以OsSUT1, 4基因做為標記基因，分析水稻上位葉葉鞘由抽穗前之儲存組織轉化成抽穗後之供源組織 (sink&#8722;source transition)的分子機制。另外，配合溫度因子對於葉鞘中OsSUT基因表現影響之探討，預期可將此些研究結果應用於改良水稻在生殖生長期及溫度逆境中，碳水化合物由葉鞘轉運至穀粒之效率。<br> Abstract: Rice leaf sheaths of upper leaves are the temporary storage sink tissues before heading, and the pre-store starch would be degraded immediately after heading. The amount of pre-store starch is highly correlated to the grain yield. In addition, efficiency of sucrose remobilization from leaf sheaths to developing grains affect the grain weight and grain-filling period, and this suggests that the rate of sucrose transport in leaf sheaths at reproductive stage plays an important role to determine the rice yield and quality. Pre-storage starch in upper leaf sheaths also serves as an alternative carbon buffer in unfavorable environment to compensate for insufficiencies of photosynthesis, and it help to reduce the negative effect on grain yield caused by environmental stresses. Therefore, improving the source function of leaf sheaths by controlling the carbohydrate remobilization would be a powerful approach to enhancing rice production. However, the regulatory mechanism of carbohydrate transport in rice leaf sheaths is still unclear. Sucrose transporter (SUT) is the key carrier for sucrose loading into phloem for carbohydrate long distance transport. In my previous studies, it has been found the rice OsSUT1 and OsSUT4 expressions were highly enhanced in rice leaf sheaths at post-heading period, and it suggested that these two SUT function as the major molecules to process sucrose loading into phloem. Therefore, in this research project, we will focus to study the regulatory mechanism of OsSUT1 and OsSUT4 gene in rice leaf sheaths to reveal the controlling of carbohydrate translocation in leaf sheaths. Moreover, OsSUT1 and OsSUT4 would be used as marker genes to study the molecular mechanism of sink-source transition in leaf sheaths during the heading period. Furthermore, the effect of temperature stress on OsSUT1 and 4 expressions would be analyzed. In long-term goal, it would be expected to improve the rice yield under environmental stresses by controlling or modifying the efficiency of carbohydrate transport from upper leaf sheaths to developing grains.水稻葉鞘蔗糖轉運蛋白riceleaf sheathsucrose transporter