Candidate Gene Analysis Of QSW.C9,a QTL For The Thousand Seed Weight In Brassica Napus L.

Brassica napus L.is one of the most important oil crops in the world.Yield improvement is an important goal of rapeseed breeding.The yield of rapeseed was determined by planting density and yield per plant,and the planting density was closely related to the plant architecture.The yield per plant was dependent on the coordination effect of the number of pods per plant,the number of per pod and the seed weight.So far,a large number of QTLs on the yield components have been reported,but only two QTLs have been cloned by the method of map-based cloning,i.e.,the QTLs(BnaA09.ARF18)and the QTLs(BnaC9.SMG7b).In the process of cloning QTL qSS.C9(BnaC9.SMG7b)by Shipeng Li[2],it was find that the seeds number of per pod increased and the seed weight decreased in NIL(Y106)simultaneously.This phenomenon may be due to pleiotropic effect of BnaC9.SMG7 b,or the interference of other genes.Further analysis revealed that the BnaC9.RINGb gene in the qSS.C9 locus may be directly involved in regulating seed weight.On the basis of this study,the candidate genes in qSS.C9 locus were analyzed by comparative genomics and molecular biology methods.The main results are as follows:1.BnaC9.SMG7 b gene complementary test: Transgenic complementary experiments showed that BnaC9.SMG7 b gene had no significant effect on seed weight.It suggested that other genes might play a role in regulating seed weight of the NIL(Y106).2.Candidate gene analysis: A comparative analysis of the candidate genes in the qSS.C9 locus showed that BnaC9.RINGb had significant genomic sequence differences between NILs and may be the target gene.The preliminary transgenic complementary test showed that BnaC9.RINGb gene negatively regulated seed weight,because it decreased the seed weight of the receptor parent HZ396 seed weight significantly.So BnaC9.RINGb probably is the target gene.3.BnaC9.RINGb homologous gene analysis: Sequence comparison showed that BnaC9.RINGb had one homologous gene in Arabidopsis thaliana,eight in Brassica napus,three in Brassica oleracea and three in Brassica rapa.4.The expression pattern of BnaC9.RINGb: GUS staining results showed that BnaC9.RINGb was expressed in cotyledons,leaves,silique wall,pistils and stamens of Arabidopsis thaliana.Subcellular localization of protein indicated that BnaC9.RINGb was located in the nucleus.5.Functions investigations of the BnaC9.RINGb homologous gene in Arabidopsis: Some of mutants were significantly higher than the wild type in the length,the width and the seed number of per pods.Although the mutant had a certain increase in the seed weight compared with the wild type,but the difference did not reach a significant level.