AtRAN1在拟南芥种子发育过程中的功能研究

北京师范大学博士学位论文ABSTRACTArabidopsis (Arabidopsis thaliana)life cycle experienced the vegetative growth and thereproductive growth.Arabidopsis seeds could be divided into three parts:the embryo,endospermand testa.Seed development in Arabidopsis thaliana undergoes an initial phase of endospermproliferation while the embryo grows slowly followed by a second phase in which the embryogrows fast by taking advantage of the endosperm nutrient.Parental genome interaction isimportant for seed growth,reflected by 1:2 proportion of the paternal to maternal genome mustbe maintained in endosperm development otherwise the seeds would developed abnormaly.Themolecular mechanisms of the parental genome interaction stillneed to be clarified.Parentalgenome interaction is associated with gene imprinting.Imprinted genesare genes expressedprimarily or exclusively from either the maternal or paternal allele,which is essential for embryodevelopment in flowering plants and mammals.However,the function of genomic imprinting isunclear.In this study,a small RAN-likeGTPase from Arabidopsis,AtRAN1,was found to express ingametophyte and developing seed in Arabidopsis.In sub-cellular localization,AtRANlis anucleus protein in interphase,in mitosis it is colocalized withspindle andphragmoplast.AtRAN/isubiquitously expressed during vegetative growth in Arabidopsis.Down regulation of AtRANIleads to smaller-size flowers and seeds,indicating that AtRAN/has a role in seed development.However,in AtRAN/knock-down line (r/-2)crossed with WT pollen,the seeds abort.On thecontrary,when WTis crossed withr/-2 pollen,the seeds aresignificantly small.The reciprocalcrosses of WT and different AtRAN/overexpression lines indicate the parental AtRAN/ratiowould be important for endosperm development.The reciprocal crosses of WT and AtRANIpromoter driving GUS line (pRAN/::GUS)show that the paternal expression of pRAN/::GUSisprohibited in endosperm in later endosperm development stage,which indicatesthat AtRAN/is apredominantly-maternally expressed imprinted gene.The proper expression of AtRAN/inendosperm is critical forthe onset of cellularization.Inr/-2crossed with WT pollen,theAtRAN/expression is abnormally high,and cellularization is delayed.In WTcrossed withr/-2pollen,the AtRAN/expression is low,and cellularization happens earlier than WT.Afterexpression examination,AtMINISEED3(AtMINI3)is positively related with AtRANI and maybethe downstream factor of AtRAN/.In conclusion,our studies demonstrate the parental AtRAN/ratio and proper expressionof AtRAN/in endosperm is critical for seed maturation.KEY WORDS:seed;AtRAN/;parental ratio;imprinting;endosperm;cellularization