Low temperatures during the booting stage reduce rice yields by causing cold-induced male sterility. We previously mapped a quantitative trait locus for cold tolerance, Ctb1, to a 56-kb region containing 7 putative genes. In this study we further mapped Ctb1 to a 17-kb region containing two genes that encode an F-box protein and a ser/thr protein kinase. The F-box protein gene was preferentially expressed in young panicles, while the ser/thr protein kinase gene was expressed in leaves and young panicles. Both genes were cloned from a cold-tolerant variety, Norin-PL8, and introduced into a cold-sensitive variety, Hokkai241, and a cold-sensitive line, BT4-74-8. The cold tolerance of T2 and T3 progenies was assessed by measuring the degree of spikelet fertility in plants treated with cool water irrigation (19 °C, 25 cm) or cool air (12 °C, 4 days). The results indicated that the F-box protein gene confers cold tolerance. Cold tolerance is associated with greater anther length, and the transgenic plants had longer anthers than non-transformed controls. The F-box protein interacts with a subunit of the E3 ubiquitin ligase, Skp1, suggesting that an ubiquitin–proteasome pathway is involved in cold tolerance at the booting stage.
水稻在孕穗期如果遇上低溫會導致雄性不育，進而造成減產(chǎn)。作者在以前的研究中定位到一個耐冷QTL Ctb1，并將其精細定位到56kb的范圍內(nèi)，該區(qū)間共有7個候選基因。在本文中作者進一步將基因定位到17kb的范圍內(nèi)，其中包含兩個候選基因，一個編碼F-box蛋白，另一個編碼絲氨酸/蘇氨酸蛋白激酶。其中F-box蛋白基因主要在幼穗表達，絲氨酸/蘇氨酸蛋白激酶基因在葉片和幼穗表達。從耐冷品種Norin-PL8中克隆到這兩個基因，分別轉(zhuǎn)進一個冷敏感的品種Hokkai241和一個冷敏感株系BT4-74-8中。通過考察冷水灌溉(19℃, 25 cm)和冷氣 (12℃, 4 days) 處理的T2、T3轉(zhuǎn)基因后代的結實率，獲得了耐冷轉(zhuǎn)基因植株，證明F-box蛋白基因是耐冷基因。耐冷性是和花藥長度相關聯(lián)的，轉(zhuǎn)基因植株和對照相比花藥長度較長。F-box蛋白和一個E3泛素連接酶亞基Skp1互作，表明泛素-蛋白酶體途徑可能參與了孕穗期的冷耐受過程。