玉米小籽粒突变体mn-Mu的基因克隆与转录组分析

Map-based cloning and transcriptomic analysis of a maize miniature kernel mutant mn-Mu

玉米籽粒大小是影响产量形成的关键因素。本研究鉴定了一个转座子随机插入的小籽粒突变体mn-Mu;该突变体相较野生型籽粒变小、种皮皱缩、淀粉含量下降,而醇溶蛋白含量升高。石蜡切片观察发现mn-Mu突变体胚乳发育迟缓,胚乳基底转移层细胞发育缺陷。遗传分析表明mn-Mu是由隐性单基因控制的突变,通过图位克隆将突变基因定位在2号染色体57.83-61.91 Mb的区间,其中已克隆的编码细胞壁转化酶的Zm00001d003776(Miniature 1,Mn1)基因在第5个外显子上存在一个1442 bp的转座子插入。等位测试证实,mn-Mu为一个新的Mn1基因等位突变体。转录组分析表明,Mn1基因功能缺失影响碳水化合物代谢、储藏物质积累、糖基转移酶活性、细胞壁生物合成和细胞周期调控等生物学过程。本研究鉴定的新的mn1等位突变体为深入解析籽粒发育的分子调控网络提供了新的遗传材料。

Kernel is the main storage organ,which accumulates nutritional compounds and determinates maize yield.In this study,we identified a miniature kernel mutant,mn-Mu,caused by a random mutator’s insertion.Compared with wild type,mn-Mu had smaller kernels,shrunken pericarp,and decreased significantly kernel weight.Compared with wild type,starch content of mn-Mu kernels decreased slightly,while zein content increased.Cytological observation showed that the development of the central endosperm and the basal endosperm transfer layer(BETL)was impaired in mn-Mu mutant compared with the wild type.Genetic analysis revealed that mn-Mu was a single gene-controlled recessive mutant.Map-based cloning indicated that the mutant gene was positioned in 57.83–61.91 Mb on chromosome 2.In this interval,Zm00001d003776 gene,which encoded CELL WALL INVERTASE 2(INCW2,Miniature 1,Mn1)previously reported,was found that a 1442 bp transposon derived from Bronze 1 locus inserted into its 5th exon.Allelic test validated that mn-Mu was a new allelic mutant of mn1.Furthermore,transcriptomic analysis revealed that the loss of Mn1 affected gene expression in the processes of carbohydrate metabolism,storage material accumulation,glycosyltransferase activity,cell wall biosynthesis,and cell cycle regulation.In conclusion,a new allelic mutant of maize Mn1(mn-Mu)was identified and transcriptomic analysis was further performed,which providing a novel maize germplasm and clues toward comprehensive understanding of molecular regulation mechanism of Mn1 on kernel development.