Gene Mining And Analysis Of Maize Kernel Moisture Content And Dehydration Rate

Maize(Zea mays L.)kernel moisture content(KMC)during harvest stage is a key trait that restricts the development of mechanized kernel harvesting technology.The higher KMC will not only increases the kernel breakage rate and the drying cost,but also seriously affects the safe storage and quality of maize kernels.Maize kernel dehydration rate(KDR)is the key trait that determines KMC during maize harvest stages.KMC and KDR are complex quantitative traits controlled by multiple genes,which are susceptible to various environmental factors.Up to now,most genetic studies on KMC and KDR have focused on initial mapping,and few quantitative trait locus(QTLs)have been confirmed by fine mapping or cloning.To excavate the key genes of KMC and KDR,and analyze the genetic structure of KMC and KDR.In this paper,the genes mining and analysis of KMC and KDR were carried out by combining the dynamic changes of KMC,single nucleotide polymorphisms(SNP)genomic mapping,gene expression transformation and protein abundance changes of maize inbred lines.The main research results are as follows:1.Based on the association population constructed by 212 maize inbred lines selected from groups Shaan A and Shaan B,three maize KMC variation types were identified: fast dehydration type,progressive dehydration type and slow dehydration type.Comparative analysis showed that the KMC of maize inbred lines in Shaan B group was significantly lower than that of maize inbred lines in Shaan A group in late kernel development stage,and the changes of KMC and KDR in the late kernel development were affected by additive effect.It was found that 42 days to 49 days after pollination(DAP)was the key stage of KMC transformation.Genome-wide association analysis was performed using temporal KMC and KDR data,98 and 279 SNPs significantly associated with KMC and KDR were detected,respectively,among which 51 SNPs were associated with the changes of KMC after 42 DAP and 113 SNPs were associated with the changes of KMC after 42 DAP.643 KMC candidate genes and 1,809 candidate genes were further screened.2.Based on the spatio-temporal transcriptome data of 8 maize inbred lines selected from fast dehydration type and slow dehydration type,the spatio-temporal transcriptome atlas in the middle and late stages of maize kernel development was constructed,and the gene coexpression network in the middle and late stages of maize kernel development was established,5,307 KMC related genes and 4,191 KDR related genes were identified.Based on the temporal proteome data of 2 maize inbred lines selected from transcriptome sequencing materials,the spatio-temporal proteome atlas in the middle and late stages of maize kernel development was further constructed,and the protein co-expression network in the middle and late stages of maize kernel development was estcblished.1,078 KMC related proteins and 653 KDR related proteins were identified.Functional enrichment analysis showed that KMC and KDR related genes and proteins were significantly enriched in starch and fatty acid biosynthesis,dehydration response,seed dormancy and other biological processes.A total of 143 genes significantly associated with KMC and KDR were identified by multi-omics analysis,and most of these genes showed significant difference in expression level between fast and slow dehydration materials.It was found that the nonsense mutation of HSP5 significantly reduced KMC and increased KDR.3.It was found that the expression transitions of genes involved in starch biosynthesis were significantly correlated with the changes of KMC and KDR.The low expression level of SBEI and SBEIIb in the late stage of kernel development of fast dehydration maize inbred lines may be the main reason for the small amylose molecular and low content of amylopectin chains of DP 6-12 in fast dehydrated maize inbred lines.At the same time,it also further improves the starch retrogradation rate of fast dehydration maize inbred lines.In summary,we analyzed the genetic basis and regulatory network of KMC and KDR in maize by multidimensional omics,and found 143 functional genes that may have potential production and utilization value,which preliminary confirmed that HSP5 significantly affected the changes of KMC and KDR,and explored the potential mechanism of starch on the changes of KMC and KDR.The results provide an important theoretical basis for improving the dehydration characteristics of maize germplasm and breeding maize varieties suitable for mechanical harvesting.