玉米籽粒突变体dek48的表型鉴定与基因定位

籽粒是玉米的主要营养储存器官,也是禾本科植物种子发育研究的模式器官。本研究对玉米自交系郑58进行甲基磺酸乙酯(EMS)诱变,获得一个稳定遗传的籽粒缺陷突变体,命名为defective kernel 48 (dek48)。该突变体籽粒皱缩扁小,百粒重显著降低,胚和胚乳发育严重缺陷,不能成苗。在玉米授粉后12 d即可观察到明显的发育缺陷,表明该突变发生在籽粒发育的早期阶段。扫描电镜观察发现dek48与野生型相比淀粉粒显著变小。石蜡切片显微观察发现dek48淀粉胚乳填充不饱满,糊粉层细胞发育不规则。遗传学分析表明,该突变性状受隐性单基因控制。进一步构建F2遗传定位群体,将该突变体基因精细定位于3号染色体7.39 Mb～7.52 Mb之间。生物信息学分析发现该区间内有6个开放阅读框,暂未发现与籽粒发育有关的已知基因,后续将通过测序和基因表达分析进一步确定候选基因。

Phenotype identification and gene mapping of defective kernel 48 mutant (dek48) in maize

Maize kernel is not only a main nutrient storage organ, but also a model organ for seed development research of gramineous plants. In this study, a stable defective kernel mutant 48 (dek48) was identified from a library of mutants of the maize inbred line Zheng58 treated with ethylmethane sulfonate (EMS). Compared with wild type, the hundred-kernel weight of the dek48 was decreased greatly due to shrunken appearance and small flat size. Moreover, the dek48 was incapable of growing into a plantlet owning to the severely defective embryo and endosperm. The obvious defective development of the mutant can be observed at 12 days after pollination (DAP), indicating that the mutation occurred at an early stage of kernel development. Microscopic observation by scanning electron microscopy (SEM) revealed that starch granule of the dek48 was significantly smaller than wild type (WT). The observation of the paraffin section demonstrated that the starch granule of dek48 endosperm was partially filled and the aleurone layer cells developed irregularly. Genetic analysis based on kernel form indicated that the mutant trait was controlled by a single recessive gene. Based on genetic F₂ population mapping, the gene of the mutant was located between 7.39 Mb-7.52 Mb on chromosome 3. The bioinformation analysis indicated that there were six new open reading frames (ORFs) and unknow genes related to kernel development in this region. Furthermore, candidate gene will be identified through sequencing and gene expression analysis in the future.