Abstract: Rice coleoptile plays an important role in the emergence of rice seedlings from soil surface and is regulated by many hormones. To identify the factors involved in coleoptile growth, this paper  a screened  mutants with abnormal coleoptile growth from  mutagenesis. One  mutant, short coleoptile 1 (scp1), showed significant short coleoptile was isolated. Moreover, the expression level of ethylene biosynthesis genes and ethylene production decreased, and  salt and drought tolerance increased  in scp1 mutant  compared with wild type. The field-grown scp1 mutant exhibited dwarf and small-grain phenotypes. Map-based cloning indicated that SCP1 located in 32.01 kb range on chromosome 5, in which there contained 5 genes. Sequencing analysis demonstrated that OsRGA1 (LOC_Os05g26890) had large fragment deletion in coding region, leading to the loss-of-function of OsRGA1. In addition, a reported mutant of OsRGA1, dwarf-1 (d1), showed similar coleoptile and agronomic phenotype with scp1 mutant, indicating that scp1 was an allelic mutant of OsRGA1. These results would deepen the understanding of the function of OsRGA1, and provided materials for investigating the molecular mechanism of ethylene in rice growth and stress tolerance.

Key words: rice, coleoptile, ethylene, salt tolerance, drought tolerance

摘要： 水稻胚芽鞘在幼苗出土过程中发挥重要作用，其生长受到多种激素的调控。为了挖掘胚芽鞘生长的关键调控因子，对水稻突变体库进行筛选，获得了一系列胚芽鞘发育缺陷突变体。其中一个突变体（short coleoptile 1, scp1）的胚芽鞘明显短于野生型，且乙烯合成基因表达水平和乙烯释放量均低于野生型，其幼苗的耐盐性和耐旱性显著提高。成株期的scp1突变体表现出矮化、小粒的表型。通过图位克隆，将SCP1基因定位在5号染色体上32.01 kb区间，该区间有5个功能基因，通过扩增与测序发现OsRGA1基因在突变体中有大片段缺失，并且与已报道的osrga1等位突变体d1具有相似的胚芽鞘表型和农艺性状，说明scp1是osrga1的另一个等位突变体。相关研究结果加深了对OsRGA1基因功能的认识，为探究乙烯调控水稻生长发育及耐逆性的分子机理提供了研究材料。

关键词: 水稻, 胚芽鞘, 乙烯, 图位克隆, 耐逆性