Under flooded conditions, the leaves and internodes of deepwater rice can elongate above the water surface to capture oxygen and prevent drowning. Our previous studies showed that three major quantitative trait loci (QTL) regulate deepwater‐dependent internode elongation in deepwater rice. In this study, we investigated the age‐dependent internode elongation in deepwater rice. We also investigated the relationship between deepwater‐dependent internode elongation and the phytohormone gibberellin (GA) by physiological and genetic approach using a QTL pyramiding line (NIL‐1 + 3 + 12). Deepwater rice did not show internode elongation before the sixth leaf stage under deepwater condition. Additionally, deepwater‐dependent internode elongation occurred on the sixth and seventh internodes during the sixth leaf stage. These results indicate that deepwater rice could not start internode elongation until the sixth leaf stage. Ultra‐performance liquid chromatography tandem mass‐spectrometry (UPLC‐MS/MS) method for the phytohormone contents showed a deepwater‐dependent GA1 and GA4 accumulation in deepwater rice. Additionally, a GA inhibitor abolished deepwater‐dependent internode elongation in deepwater rice. On the contrary, GA feeding mimicked internode elongation under ordinary growth conditions. However, mutations in GA biosynthesis and signal transduction genes blocked deepwater‐dependent internode elongation. These data suggested that GA biosynthesis and signal transduction are essential for deepwater‐dependent internode elongation in deepwater rice.
在水淹環(huán)境下，深水稻的葉和節(jié)間能夠伸長到水面之上來捕獲氧和防止水淹。我們以前的研究發(fā)現(xiàn)在深水稻中存在3個(gè)調(diào)控深水依賴的節(jié)間伸長的主效數(shù)量性狀位點(diǎn)（QTL）。本文我們研究了深水稻年齡依賴的節(jié)間伸長。通過對近等基因系（NIL）的生理和遺傳研究，我們還研究了深水依賴的節(jié)間伸長與植物激素赤霉素之間的關(guān)系。水淹條件下，深水稻六葉期前節(jié)間不能伸長。此外，水淹依賴的節(jié)間伸長發(fā)生在六葉期的第六和第七節(jié)間。這些結(jié)果表明深水稻在六葉期之前節(jié)間伸長不能起始。超高效液相色譜串聯(lián)質(zhì)譜（UPLC-MS/MS）檢測到深水稻中赤霉素GA1和GA4的積累是水淹依賴的。此外，GA抑制劑能夠終止深水稻水淹依賴的節(jié)間伸長。相反，外施GA使得正常條件下的節(jié)間伸長跟水淹相似。然而，GA生物合成(OsGA20ox2)和信號傳導(dǎo)基因(SLR和GID1)的突變能夠阻斷深水依賴的節(jié)間伸長。這些數(shù)據(jù)表明GA生物合成和信號傳導(dǎo)對于深水稻在水淹環(huán)境下的節(jié)間伸長過程發(fā)揮著重要作用。