Tolerance to abiotic stress is an important agronomic trait in crops and is controlled by many genes, which are called quantitative trait loci (QTLs). Identification of these QTLs will contribute not only to the understanding of plant biology but also for plant breeding, to achieve stable crop production around the world. Previously, we mapped three QTLs controlling low-temperature tolerance at the germination stage (called low-temperature germinability). To understand the molecular basis of one of these QTLs, qLTG3-1 (quantitative trait locus for low-temperature germinability on chromosome 3), map-based cloning was performed, and this QTL was shown to be encoded by a protein of unknown function. The QTL qLTG3-1 is strongly expressed in the embryo during seed germination. Before and during seed germination, specific localization of beta-glucuronidase staining in the tissues covering the embryo, which involved the epiblast covering the coleoptile and the aleurone layer of the seed coat, was observed. Expression of qLTG3-1 was tightly associated with vacuolation of the tissues covering the embryo. This may cause tissue weakening, resulting in reduction of the mechanical resistance to the growth potential of the coleoptile. These phenomena are quite similar to the model system of seed germination presented by dicot plants, suggesting that this model may be conserved in both dicot and monocot plants.
作物對非生物脅迫的耐受性是重要的農(nóng)藝性狀之一，由被稱為數(shù)量性狀基因座(QTL)的許多基因所控制。這些QTL的分離不僅有助于對植物生物學的認識，同時有助于提高作物的產(chǎn)量。之前我們定位到了3個控制水稻發(fā)芽期的低溫耐受性（稱為低溫發(fā)芽勢）的QTL。為了更好的認識其分子機理，我們對其中的一個QTL qLTG3-1進行了圖位克隆。qLTG3-1編碼一個功能未知的蛋白。在種子發(fā)芽過程中，qLTG3-1在胚強烈表達。在種子發(fā)芽之前及過程中，在覆蓋胚的組織如覆蓋胚芽鞘和種皮糊粉層的上胚層可以觀察到特異的β-葡糖苷酸酶染色。qLTG3-1的表達與覆蓋胚的組織的液泡化緊密相關(guān)。這可能引起組織松弛而導(dǎo)致胚芽鞘生長的機械阻力降低。這些結(jié)果與雙子葉植物的種子發(fā)芽模式十分類似，表明這樣的發(fā)芽模式在雙子葉植物和單子葉植物中都很保守。