Functional Analysis Of AtSYP3 Family,the SNAREs Involved In Storage Protein Transport In Arabidopsis

Higher plant seeds deposit massive storage proteins to provide source of N and C during germination and early development.Seed storage proteins are synthetized as large precursors on the rough endoplasmic reticulum,and then are transported to vacuole where they are processed into mature forms.Storage protein transport mainly depends on vesicle trafficking.Vesicle trafficking includes vesicles budding,directional movement,tethering,anchoring and membrane fusion.Study on gene function of the factors working on storage protein transport pathways will help to understand mechanism of vesicle trafficking and influence factors on seed qualities.This will lay the theoretical foundation of molecular breeding to improve quality of seed storage proteins.SNARE proteins include Qa-,Qb-,Qc-and R-SNARE.They form SNARE complex and mediate membrane fusion,playing an important role on the process of membrane fusion.Qa-SNARE is the most important SNARE,it is essential to formation and stabilities of the SNARE complex.In yeast,Golgi-localized Sed5p interacts with other SNAREs and regulates membrane fusion between the ER and Gogli apparatus.In Arabidopsis,the Gogli-localized Qa-SNARE is unclear.According to amino acid homology analysis,AtSed5/AtSYP3 is predicted as Gogli-localized Qa-SNARE.AtSYP3 family includes AtSYP31 and AtSYP32,their function remains unclear?In this study,we isolated the T-DNA insertion mutants of AtSYPS1 and AtSYP32,and made transgenic plants of RNAi and overexpression,and used them to perform a serious analysis.We found that AtSYP31 and AtSYP32 are localized on the Golgi apparatus.AtSYP31 gene defect and overexpression affected transport of seed storage proteins,while AtSYP32 did not.AtSYP31 gene defect suppressed plant early development,but promote the development at later stages.AtSYP31 gene overexpression affected the whole stages of plants growth and development.AtSYP32 plays an essential role in regulating plant growth and development.AtSYP32 defect might affect development of embryo,resulting in homozygotes lethal.AtSYP32 knock down led to abnormal growth,while AtSYP32 gene overexpression suppressed the initial growth of the plant.Although we got progress on understanding AtSYP31 and AtSYP32,but which is the Golgi-localized Qa-SNARE is still unclear.It is necessary to make futher study to explore it.