Fine Mapping Of The Plant Height Gene ZmDLE1 In Maize

The plant height of maize is an important trait for ideal plant architecture breeding.Plant height not only affects the mechanization of harvesting,but also relates to lodging resistance and yield.Therefore,cloning related maize plant height genes and analyzing their functions have important theoretical and practical value.In this study,the dwarf low ear mutant dle1 obtained by EMS mutagenesis of the maize inbred line LY8405 was used as the material to investigate and analyze the phenotypic and cytological characters.Then,using a large isolated population combined with the development of polymorphic markers in the target segment and RNA-Seq sequencing methods,the dwarf mutation site was finely mapped,The key candidate gene was preliminarily determined which is named as ZmDLE1.The main results of this study are as follows:1.Identification of Agronomic Traits of dle1.Compared with wild-type LY8405,the plant height and ear height of mutant dle1decreased by 35.0%and 62.9%,respectively,and the difference reached a significant level（p<0.05）.Although the mutant dle1 had normal seed set,its grain length was significantly shorter（p<0.01）.the number of internodes under the panicle of dle1 was one less than that of LY8405.Cytological observation showed that the length of the internodes in the longitudinal section of the mutant dle1 was significantly shorter than that of LY8405（p<0.01）.These results suggested that the shortened longitudinal length of internode cells was the reason for the reduction of plant height and ear height of dle1.2.Fine mapping of ZmDLE1.Statistical analysis using the（dle1×Mo17）F₂ segregating population showed that the dwarf phenotype of dle1 was controlled by a single-site recessive gene（c²=2.854）,which was named as ZmDLE1.Using BSA-seq and RNA-seq,the ZmDLE1 gene was located between the maize chromosome 1 markers TIDP6556 and In Del-9;then the F₂ large segregated population obtained by（dle1×Mo17）was used to develop the target segment polymorphism markers.ZmDLE1 was further located within the approximately 620 Kb physical interval between markers In Del-11 and In Del-26.3.Identification of ZmDLE1 key candidate genes and analysis of mutation sites.Within the 620 Kb target segment,there were a total of 16 annotated genes;According to the differential expression analysis,there were 2 differentially expressed genes in this region.Using the genotypes and phenotypic data of plant height and ear height of 513associated populations,the candidate segment association analysis was carried out,and it was found that there were variation loci significantly associated with plant height and ear height in Zm00001d033231.The results of q RT-PCR showed that the expression level of Zm00001d033231 gene in dle1 was significantly lower than that in the wild.Zm00001d033231 encodes an Expansin family protein,and the Expansin-4 protein encoded by its homologous gene AT2G45110 in Arabidopsis is involved in hormone regulation,cell expansion and other plant growth processes.Therefore,it is preliminarily speculated that Zm00001d033231 is candidate gene of ZmDLE1.Through the sequence comparison analysis between the mutant and the wild type,it was found that the bases at positions 255,274,and 215 in the mutant dle1 were changed from G to A,The original arginine was changed to glutamine,and the variation was located in the conserved functional domain of the Zm00001d033231 protein.It is preliminarily speculated that the base change in the CDS region may be an important functional variation site of the gene Zmdle1 leading to the dwarf phenotype.