Fine Mapping The Fertility Restorer Gene Rf5 For C-cytoplasmic Male Sterility In Maize

Maize is an important food and feed crop which plays an invaluable role in the development of the world economy.In 2012,China’s corn acreage and yield rank first among food crops.Corn plays a vital role in solving the problem of food security.Since the use of hybrid corn in the mid-1930s,hybrid maize has become an important measure of world corn yield.In China,the popularizing rate of hybrids has reached more than 95%.Because of the stable fertility restoration,diseases invasion for cytoplasmic specificity and many other factors,seed production work needs artificial and mechanical emasculation,which increase the cost of producing.In the present production condition,"three-line system" of cytoplasmic infertility still has great potential in seed production.Male sterility can be divided into nucleic and cytoplasmic sterility.Because cytoplasmic infertility can achieve "three-line system ",it is the main type of application on production.According to the principle of specificity restorer gene for fertility restoration of male sterile line,cytoplasmic male sterility can be divided into T,S,C three types.C-type cytoplasmic male sterility is sporozoites infertility,with highly stable sterility,easy restoration and other advantages in production which has been widely applied.However,the molecular mechanism of the restoration of C-type cytoplasmic male sterile is so far from clear that the molecular mechanism of infertility and restoration is not deeper than T-type and S-type,which is still at the level of the mechanism of the restoration of classical genetics and gene mapping.In this study,we used the male sterility line Cms-CMo-17(rf5rf5)and the restorer line Cms-C6233(Rf5Rf5)as experiment materials to construct a BC1 segregation group.B73 genomic information was used to develop a large number of SSR and Indel molecular markers for the restorer gene fine mapping.Based on fine mapping and the use of B73 genome sequence information,restorer gene Rf5 candidate genes were obtained.The main findings are as follows:1、By using sterile line Mo-17(rf5rf5)and restorer line 6233(Rf5Rf5),we constructed a BC1 segregating population which were under fertility survey conducted in the field.And infertility and fertility plant conform to the ratio of 1:1,in line with Mendelian inheritance,indicating that differences in fertility study materials were controlled only by a pair of genes,Rf5.2、On the basis of preliminary studies on the screening of all-known markers on maize chromosome 2 2.08、2.09 and 2.10 bin,the polymorphic markers obtained were used for screening segregating populations.According to the results of the analysis,the restorer gene Rf5 were positioned between primers bnlg1520 between umc1736.By expanding segregation population to 32,000 individuals and using the maize genome sequence,278 SSR and Indel markers were developed,and 23 pairs of polymorphic molecular markers were used for fine mapping of Rf5.The nearest markers between the target gene are chr2.09-36 and chr2.09-6+1,which Physical distance is 82,284 bp.3、Within the region of this chromosome and using B73 maize genome sequence information,6 structural gene were obtained.All the genes were under functional annotation and metabolic pathway analysis and in these six genes,two of PPR structural gene,a transcription factor-coding genes,two genes involved in signal transduction,and a gene of unknown function were detected.Since reported male sterility restorer gene in rice is now PPR structural gene,and therefore two PPR structural genes were identified as C-type cytoplasmic male sterility in maize fertility restorer gene Rf5 candidate genes.The structure of these two PPR genes were under structural analysis and were found to have a plastid localization signal gene sequences as well as the differences of the gene amplification in the sterile and restorer lines.So the gene is identified as a Rf5 candidate gene.