Study On The Emerging And Development Of Endopolyploidy In Maize

Endopolyploidy is a phenomenon in which adjacent cells in the same individual have multiple ploidy nuclei type.Endopolyploidy is caused by DNA endoreplication,a special type of mitosis with normal DNA synthesis and a lack of cell division;it is a common phenomenon and plays an important role in plant development.In this study,in order to systematically investigate the temporal and spatial specificity of endopolyploidy in maize,flow cytometry was used to finely measure the endopolyploidy patterns in developing tissues and organs from seedling to maturity;the distribution pattern of endopolyploidy among 119 inbred lines from two different heterotic breeding populations,as well as the effect of drought stress on endopolyploidy were investigated.Some correlation analysis was used to study potential biological significances of endopolyploidy in maize.Meanwhile,a genome-wide association study(GWAS)was used to identify significant SNPs and screen candidate genes related to endopolyploidy.The main research results are:1.Endopolyploidy shows organ-specific and stage-specific patterns in maizeEndopolyploidy was observed in most organs at various developmental stages except in expanded leaves and filaments.Endoreplication in plants most commonly occurs in tissues that develop mass quickly and have high metabolic activity.Ploidy is also higher in some highly lignifed transport-associated tissues.During tissue development,the ploidy increased with maturity in all organs except the leaves.The roots have the highest degree of endopolyploidy in two stages(the albumen stage and the large trumpet stage)that are most vigorous.The endosperm showed the highest C value among all organs and most types of polyploid nuclei were found at 20 DAP.2.Drought stress has a significantly effect on endopolyploidization.Endopolyploidy of roots suffering from drought stress was significantly affected by both time under stress and PEG concentration,and there was a significant synergistic effect on endopolyploidy between time under stress and PEG concentration.3.The results of multiple comparisons showed no significant differences in C values among the seven subgroups,which demonstrated that the group structure of germplasm had no effect on the level of endopolyploidization(the C value).Endopolyploidy were significantly correlated with the length of the whole seedling and the length of the main root,but was not related to these agronomic characters or GY in maturity stage.4.A genome-wide association study(GWAS)identified a total of 9 significant SNPs associated with endopolyploidy(C value)in maize,and 8 candidate genes that participate in cell cycle regulation and DNA replication were uncovered in 119 maize inbred lines;however,their association with endopolyploidy requires further investigation.