玉米籽粒皱缩突变体sh2021的表型分析和基因定位

Morphological characterization and genetic mapping of shrunken endosperm mutant sh2021 in maize

【目的】分析玉米籽粒皱缩突变体的表型特征并进行籽粒相关基因的精细定位,为揭示该基因调控玉米籽粒发育的分子机制奠定基础。【方法】以玉米自交系‘B73’种植过程中籽粒自发突变个体为材料,命名为shank2021(sh2021),对其形态学和细胞学特征进行观察;构建分离群体,通过混合群体分离分析法(Bulked segregant analysis,BSA)对基因进行初步定位,筛选交换单株进一步缩小定位区间,最后结合转录组测序及基因功能注释推测控制籽粒缺陷性状的候选基因。【结果】与野生型相比,sh2021籽粒凹陷皱缩、颜色加深、籽粒排列不规则,且百粒质量降低。扫描电镜观察发现,与野生型相比,sh2021胚乳细胞和淀粉粒均显著变小,且淀粉粒大小不均匀。遗传分析结果表明,sh2021是由单个隐性基因突变所致。利用BSA分析方法将目的基因定位在3号染色体末端约13.25 Mb区域。进一步扩大分离群体筛选交换单株,将目的基因定位在标记ID5与ID9之间的529.60 kb范围。通过sh2021和野生型的转录组测序,结合基因功能注释结果,预测Zm00001d044119、Zm00001d044120、Zm00001d044122、Zm00001d044129、Zm00001d044142这5个基因可能是影响玉米籽粒发育的重要候选基因。【结论】sh2021的发现与鉴定为进一步深入解析玉米籽粒发育的遗传机制提供了丰富的试验材料,同时也为后续相关基因的克隆和功能解析奠定了基础。

【Objective】To analyze the phenotypic characteristic of maize shrunk endosperm mutant and fine mapping of related genes,and lay a foundation for further understanding molecular mechanism of maize kernel development.【Method】The spontaneous shrunk endosperm mutant shank2021(sh2021)was isolated from maize inbred line B73.Morphological and cytological characteristics were observed.A segregating population was developed,and the bulked segregant analysis(BSA)was used for preliminary gene mapping.The recombinant plants were screened for further narrowing the mapping interval.Finally the candidate genes controlling grain defect traits were speculated by transcriptome sequencing combined with gene function annotation analysis.【Result】Compared with wild type,sh2021 displayed sunken and shrunken kernels,darker color,irregular grain arrangement,and lower 100-grain weight.The scanning electron microscope observation revealed that sh2021 had smaller endosperm cells and starch granules,and the starch granules were varied in size.The genetic analysis results indicated that sh2021 was caused by a single recessive gene mutation.The BSA indicated that the target gene was located on a 13.25 Mb fragment at the end of chromosome 3.By further expanding the segregating population and screening recombinant plants,the target gene was narrowed down to an interval of 529.60 kb between markers ID5 and ID9.Transcriptome sequencing and gene annotation of sh2021 and wild type indicated that Zm00001d044119,Zm00001d044120,Zm00001d044122,Zm00001d044129,and Zm00001d044142 mighted be candidate genes controlling maize kernel development.【Conclusion】The identification of sh2021 provides abundant experimental materials for the study of kernel development,and lays a foundation for further map-based cloning and functional analysis of sh2021.