Study On The Regulation Of Maize Biomass By Cell Cycle Switch Protein APC/C^ZmCCS52B

Maize is an important food crop in agricultural production,and its biomass is directly related to food security and economic development.Therefore,the cultivation of ideal new plant types and the improvement of biomass have extremely important significance for the improvement of corn economic value,and it has always been an important scientific issue of concern.In order to clarify the molecular mechanism of maize biomass regulation,we screened dwarf mutants from the EMS mutagenesis library of maize inbred line B73.By using the method of EcMutMp,we located the mutation site and proved that the mutant was caused by the mutation of ZmCCS52B,a component encoding gene of APC/C late cell cycle promoting complex.We obtained 5 alleles of the gene from the mutant library and named them zmccs52b-1-zmccs52b-5,respectively.In this study,phenotypic analysis was mainly performed using zmccs52b-1(strong mutant)and zmccs52b-4(weak mutant).Detailed phenotypic analysis showed that the dwarfing phenotype of zmccs52b mutant was caused by the shortening of stem segments,and each stem segment was uniformly shortened.By observing the size of the epidermal cells in the leaves,it was found that the phenotype of zmccs52b mutant was caused by the decrease of the number of cells per unit area of the mutant.After pollination for different days,seed sections were analyzed and it was found that zmccs52b mutant showed obvious defect phenotype in grain development,mainly the endosperm became significantly smaller.In pollination in the 12 days of endosperm cell size analysis found that zmccs52b mutant cell number per unit area decreases,the flow cytometry analysis results show that the mutation in the body copy,affected the normal cells to complete the cell division,resulting in complete from G2 to M phase reducing the number of cells,characterized by reduces total cell number,plant biomass decreased.ZmCCS52B is a homologous protein of human and animal Cdhl and an activator of APC/C complex in the cell cycle,which is involved in the process of specific APC/C substrate recognition.In order to analyze the molecular mechanism of ZmCCS52B regulating the biomass changes such as the height of maize plants,we screened the proteins with strong interactions with ZmCCS52B by yeast double hybridization,and found that ZmCCS52B and ZmWEE1 had strong intracellular interactions.As a protein kinase,ZmWEE1 can inhibit the kinase activity of CDK1 and thus inhibit the entry of cells into mitosis.ZmWEE1 contains KEN Box of the substrate specifically identified by APC/C complex.After the mutation of the base in KEN box,we found that ZmWEE1 could not interact with ZmCCS52B.At the same time,we found that the content of ZmWEE1 protein in zmccs52b mutant increased significantly,and the content of ZmWEE1 increased after treatment with MG132.These results suggest that ZmCCS52B is likely to participate in the regulation of cell cycle through the specific recognition and degradation of substrate ZmWEE1 by 26S proteasome,and ultimately affect the accumulation of corn biomass.To elucidate the biochemical relationship between ZmCCS52B and ZmWEE1 and explore its mechanism in cell cycle regulation,it will help us further analyze the molecular mechanism of ZmCCS52B involved in corn biomass accumulation,and provide theoretical basis and material support for improving cell biomass by regulating cell cycle.