Identification and Fine Mapping of Semidwarf Gene iga-1 in Rice

To understand the genetic mechanism of the semidwarf rice (Oryza sativa L.) mutant, iga-1, isolated by mutagenesis of outer space treatment, the mutant gene was identified through genetic analysis and molecular marker-aided fine mapping. Two iga-1 lines, CHA-2 and CHA-2N, showed great variations in agronomic traits compared to their wild-type parent Texianzhan 13, but their internodes had normal ratio in length, which indicated that they are dn type of dwarfing. Exogenous gibberellic acid (GA3) could neither restore the wild-type plant height in CHA-2 and CHA-2N nor elongate plants of both lines as tall as Huiyang Zhenzhuzao and Aijiaonante treated with the same concentrations of GA3; the concentrations of endogenous GA3 in both iga-1 lines were not affected by the presence of iga-1 gene; and the activities of α-amylase in endosperm of both iga-1 lines were enhanced the same as their wild-type parent. Thus, iga-1 gene proved to be independent of GA3. Using a large F2 population (3000 individuals) derived from the cross between CHA-2 and a semidwarf japonica rice variety, 02428 (sd1sd1Iga-1Iga-1), the iga-1 gene was fine mapped between the insert/deletion (InDel) markers DL18 and DL19 on chromosome 5, with the physical distance of 32.01 kb. In this region, 5 open reading frames were predicted, including the gibberellin-insensitive dwarf mutant gene D1. However, D1 gene was not the candidate locus of iga-1 because there was no sequence difference between Texianzhan 13 and CHA-2 or CHA-2N.

摘要在前期通过空间诱变获得半矮秆隐性突变基因iga-1的基础上, 进一步对iga-1进行鉴定。农艺性状调查表明携带iga-1的矮秆株系CHA-2、CHA-2N与原种特籼占13相比存在明显变异。节间长度测量显示CHA-2、CHA-2N节间比例正常, 属dn型。外源GA3处理、内源GA3测定和α-淀粉酶活性检测揭示iga-1与GA3调控无关。利用CHA-2与粳稻品种02428杂交获得的F2群体将iga-1定位在水稻第5染色体两个InDel标记DL18和DL19间32.01 kb的物理距离内。该区域有5个阅读框架, 其中包括赤霉素信号传导调控基因D1。序列分析表明CHA-2、CHA-2N和特籼占13在D1位点上基因组序列不存在差异, 推测D1并非iga-1的候选基因。比较水稻第5染色体上其他矮秆基因发现iga-1可能与半矮秆基因sd-7来自同一位点。