Mechanism Of Seed Development Regulated By HRD3A Gene In Arabidopsis

Seed size is one of the major factors affecting crop yield.It will be helpful for crop high-yield breeding to indentify the key genes controlling seed size and explore the molecular mechanism of seed size regulation.HRD3A is involved in endoplasmic reticulum-related plant stress response and is an important E3 ubiquitin ligase in unfolded protein reaction(UPR).It plays a key role in refolding of unfolded proteins and degradation of misfolded proteins.Mutation of HRD3 A gene results in smaller seeds and 1000-grain weight of hrd3a-1 mutant decreased by 20% compared to wild type(WT).The results of differential interference contrast microscope(DIC)observation showed epidermal cells and embryonic cotyledon epidermal cells were smaller than those of WT.The reciprocal cross-hatch experiments of hrd3a-1 and wild type were carried out and it was suggested that HRD3 A has a maternal tissue effect.To further determine HRD3 A gene function,we constructed PHRD3A::HRD3A-GUS and 35S::HRD3A-GUS vectors,and transferred them into hrd3a-1 mutants,respectively.The hrd3a-1 mutant small seed phenotype was restored.The expression pattern of HRD3 A gene was also analyzed through the GUS activity determination of PHRD3A::HRD3A-GUS transgenic plants.The results showed that HRD3 A was expressed in seedlings,young styles,pollen grains,ovules,and seeds at 3 days after pollination(DAP),6 DAP,and 9 DAP.Of mutant hrd3a-1 the transcriptome sequencing results were analyzed,and found that some of the differentially expressed genes related to cell elongation,including members of the family of auxin synthetic factor YUC,members of the family of auxin response factor ARF members of the family,the TCP and cytochrome P450 family,the differentially expressed genes in ARF members of the family of KEGG analysis,found hrd3a-1 mutant transcription of auxin response factor ARF lowered significantly and ARF promote plant cell elongation.KLU/CYP78A5 is one member of the cytochrome P450 family.It promotes the division and elongation of the bead cells through the maternal effect and plays an important role in regulating seed size.We obtained the hrd3a-1 klu double mutant through cross experiment.The phenotypes of hrd3a-1 klu double mutant were more severe than two single mutants.CYP78A7 and KLU genes are functionally redundant for seed growth and development.CYP78A7 gene is transcription down-regulation in the background of hrd3 a mutant.In conclusion,we believe that HRD3 A may be promoted by promoting the transcription of CYP78A7 and the elongation of the integument by the cells,thus allowing the seeds to develop normally.