斑点叶突变体是指植物在正常生长条件下叶片或叶鞘上自发形成、且与病原菌侵染产生的病斑类似的一类突变体,筛选并研究斑点叶突变体对揭示植物抗病反应机理具有重要意义。为了进一步研究斑点叶的形成机制,本文通过EMS诱变品种宽叶粳(KYJ),筛选得到两个斑点叶突变体spl101和spl102。这两个突变体在生长发育晚期(抽穗期以后)形成严重的类病斑。遗传分析表明,spl101和spl102均受隐性单基因控制。利用Mutmap方法对候选基因进行克隆,结果显示,spl101和spl102的候选基因均为OsEDR1,该基因与类病斑发生有关。在spl101中,OsEDR1基因突变发生在第6外显子和第6内含子的交接处,该突变导致第6内含子的错误识别,最终造成移码突变。在spl102中,OsEDR1基因突变发生在第10外显子上,导致一个苯丙氨酸(F)变成半胖氨酸(C)。因此,本研究鉴定了两个新的OsEDR1等位突变,对OsEDR1抗病反应机理的进一步研究及丰富水稻种质资源具有积极意义。同时验证了利用Mutmap方法克隆水稻突变基因的有效性。

Spotted-leaf mutants form spots in leaves or leaf sheaths under normal condition. The spotted-leaf phenotypes are similar to hypersensitive reaction of plants attacked by pathogen. Identification and characterization of the spotted-leaf mutants are helpful for understanding the mechanisms of resistance to plant diseases. Here, we identify two spotted-leaf mutants spl101 and spl102 from an EMS-treated elite japonica cultivar KYJ (Kuanyejing). spl101 and spl102 form serious spots at the late heading stage. Genetic analyses show that the spotted-leaf phenotypes of both spl101 and spl102 are caused by a single recessive mutation, respectively. By employing the Mutmap method, we reveal that both spl101 and spl102 contain mutations in the OsEDR1 gene. The spl101 mutation occurs in the 5°-splicing site of the 6 ^th intron of OsEDR1, which causes abnormal recognition of the 6 ^th intron and leads to the frameshift mutation. The spl102 mutant contains a mutation in the tenth exon of OsEDR1, resulting in an amino acid change from the phenylalanine (F) to the cysteine (C). OsEDR1 has been reported to regulate pathogen-resistant reaction, and loss of OsEDR1 function produces similar phenotypes to those of spl101 and spl102. Here, two newly identified alleles of OsEDR1 will be benefit for further understanding the molecular mechanisms of the OsEDR1 gene in disease resistance, and will be helpful for enriching the rice germplasm resources. In addition, our results also validate the effectiveness of the Mutmap method in cloning the candidate mutations.