Identification Of Floral Traits And Self-crossing Seed Setting Rate Between Oryza Rufipogon And Oryza Sativa

Oryza rufipogon is a wild relative of cultivated rice,it has many excellent genes.Floral traits are one of the main factors affecting plant mating systems.The phenotypic morphological characteristics and flowering habits of floral organs are important factors affecting yield.During the long-term evolution of O.rufipogon,floral traits morphology and flowering habits have undergone significant changes,but the molecular regulation mechanism of floral traits morphological changes and floral organ development in O.rufipogon still not clear.The results of previous studies clarified that MADS-box transcription factor plays a key role in the regulating growth and development of floral traits.At present,only little research on O.rufipogon of MADS-box gene,and during the process of domestication of rice,and the gene type,quantity,evolutionary relationship of MADS-box and the function of floral organ development are not clear.In this study,we first investigated the phenotypic traits and flowering habits of O.rufipogon and Nipponbare cultivar of O.sativa（japonica group）floral traits,The fertility of pollens was detected by I₂-KI staining,Bioinformatics analysis for systematic identification and analysis of O.rufipogon and Nipponbare MADS-box gene families,MADS-box gene expression models were analyzed and verified by quantitative real-time PCR,Combining the difference in phenotypic traits of floral traits and the difference in gene expression,the reason why the rufipogon and Nipponbare floral traits evolved during the evolution process was clarified.The main results of this study of are as following:（1）To clarify the variation of floral traits between O.rufipogon and Nipponbare,we investigated 20 traits mainly about floral organ phenotypic shape,flowering habit,the seed setting rate,etc.It was found that the phenotypic shape of O.rufipogon and Nipponbare significant difference.The anther length and width,filament length and stigma length of O.rufipogon were much longer than those of Nipponbare.The opening angle of glume and the length of glume of O.rufipogon were also larger than those of Nipponbare.In addition,the appearance of the O.rufipogon glume is also significantly different.The ratio of length to width ratio of the O.rufipogon glume is 3:1,while that of the Nipponbare is 2:1.O.rufipogon n has obvious awn with a maximum length of8.3cm,but Nipponbare has no obvious awn.Among the traits investigated,the traits with great differences were stigma exhalation rate and self-crossing seed setting rate.The self-crossing seed setting rate of O.rufipogon only 5.8%,but that of Nipponbare was 99%.It can be see that the difference in floral traits of O.rufipogon and Nipponbare may be one of the main reasons cause the difference in seed setting rate.（2）Pollen fertility is a key factor for plant fertility.In order to detect the fertility of O.rufipogon and Nipponbare pollen,this experiment use I₂-KI staining to detect pollen fertility.According to the staining experiment of I₂-KI solution,it was found that the fertility of O.rufipogon powder was very low,only about 45%of the pollen grains were fertile,and all the Nipponbare pollen grains were successfully dyed dark blue,and the pollen grains were regular and full round.Therefore,pollen sterility or abortion may be one of the main reasons for the low seed setting rate of O.rufipogon.（3）MADS-box are important genes that regulates the development of floral traits.The variation of floral trait may be caused by the regulation and expression changes of MADS-box gene.In this study,71 numbers and 58 numbers of MADS-box genes were identified by analyzing the transcriptomic databases of O.rufipogon and Nipponbare.Through cluster expression analysis,it was found that the expression of MADS-box gene was significantly different in the panicle of O.rufipogon and Nipponbare,while the expression of genes with high expression in the panicle of O.rufipogon,such as the gene Os MADS1,Os MADS2,Os MADS18,Os MADS21,their expressions is completely opposite.（4）In order to test the accuracy of cluster expression analysis,10 genes with differentially expressed were randomly selected in this study,and the expression levels of these genes at different panicle stages were analyzed by q RT-PCR.In addition,the expression patterns of some genes such as Os MADS1,Os MADS2,Os MADS18,Os MADS21 between O.rufipogon and Nipponbare panicle found were contrary,this result is consistent with the results of cluster expression analysis.（5）In summary,during the domestication of O.rufipogon into cultivated rice,the phenotypic traits of flower vessels changed significantly,and the changes of awn length,glume shell length and width ratio,stigma exposure rate and self-crossing seed setting rate were significant.In the process of artificial selective domestication,the pollen fertility which affects the seed setting rate is obviously improved.Through the systematic analysis of the mads-box gene family which regulates the development of floral organ,it is found that the internal reason for the variation of floral organ may be caused by the change of the gene expression amount in the development of floral organ.