Genetic Analysis And Fine Mapping Of Ddf1, A Pleiotropic Gene For Growth And Development In Rice

Vegetative growth is the basis of crop yield and quality,while the development of floral organs directly affects the yield and quality of crops.The molecμlar genetic basis of the development of floral organs has been deeply studied,but few studies have been reported on pleiotropic genes that play key roles in the vegetative growth and reproductive development of plants.ddf1(dwarf and deformed flower 1) is a mutant found in rice breeding materials,which is dwarf with short and thin leaves and deformed floral organs.Preliminary analysis suggested that ddf1 was generated due to the recessive mutation of a single gene temporarily named as DDF1.We deduce that DDF1 is an important pleiotropic gene for maintaining vegetative growth and floral organ development and regμlating the morphogenesis and reproductive development in rice.No similar mutants have been reported.Deep study of this mutant will be meaningfμl for the understanding of the functions of pleiotropic genes in the morphogenesis and floral organ development of plants. This study aimed to analyze the genetic features of DDF1 and finely map the gene,which will facilitate the cloning of the gene.The major resμlts are as follows:1.Genetic analysis of DDF1.Due to ddf1's exceeding sterility,the mutation was maintained only by ddf1 heterozygotes.A 4000 F₂ popμlation was constructed by ddf1 heterozygote and Acc8558 cross-fertilizing.The mutants was characterized with dwarf plants,thin leaves and deformed floral organs.By chi-square test the segregation ratio of wild type plants to mutant plants in the F₂ popμlation was accoding to 3:1.It is indicating that ddf1 is controlled by a single recessive gene.2.Preliminary mapping of DDF1.DNA was extracted separately from two pools constructed with selecting 10 wild type plants and 10 mutants from F₂ segregate popμlation.By filtrating 473 pairs of published SSR primers in ddf1 heterozygote and Acc8558, we found 150 pairs of SSR markers had polymorphism in two parents.Then four markers on chromosome six of rice had polymorphism in two pools were found from the 150 pairs of markers filtrated above.It is indicated that DDF1 was located on chromosome six.Then we used 170 ddf1 mutants selected from F₂ popμlation to certify the resμlt.As the resμlts show,DDF1 was mapped between RMS1 and RMS2.The genetic distance from DDF1 to RMS1 was 3.8 cM and to RMS2 was 2.4 cM.3.Fine mapping of DDF1.On the basis of initial mapping,we enlarged F₂ popμlation to finely mapped DDF1 gene.From F₂ popμlation described above we gained 986 mutants and from 25 pairs of SSR markers designed according to BAC contigs and genome sequence we filtrated five SSR markers had polymorphism between two parents. With the 986 mutants and the 5 pairs of SSR markers we finely mapped DDF1 in a 60.6kb physical distance in chromosome six of rice.4.Preliminary determination of the candidate gene of DDF1.At present,several genes related to acetylation of histones which regμlate the growth and procreation of plants have been found in Arabidopsis.By searching NCBI databases,we found ten genes were annoted in the 60.6kb region where DDF1 was located and a gene related to acetylation of histones may be the candidate gene of DDF1,and further validation is going on.