The REM(Reproductive Meristem)gene family,a major clade of the B3DNA-binding domain superfamily,have a large number of genes and significant functional differentiation.It has been indicated to be mainly expressed in reproductive meristem and floral organs,however,their evolutionary and functional profiles during flower development and growth are still uncertain.In this study,we first identified and analyzed the REM gene families of 12 representative angiosperms.The phylogenetic analysis,subfamily classification,and chromosomal localization of REM gene familiy in Rosa chinensis were carried out.Secondly,rose genotypes Old Blush and Viridiflora were used as experimental materials to explore the specific expression patterns of REM gene family during different developmental stages and different tissues,and then a co-expression network with REM family as the center and biased to the genes related to flowering regulation,and flower development as well as cell proliferation or cell expasnsion,were constructed.Finally,we screened out the transcription factors of Rc REM18 with significant changes in expression from the REM family of Rosa chinensis.Through the combination of transgenic Arabidopsis thaliana technology and VIGS gene silencing technology,we further studied the function of Rc REM18 gene in rose,and preliminarily explored the molecular mechanism and its functional regulation.The main results were listed below:1.In order to understand the evolutionary history of REM gene family in angiosperms,we conducted the whole genome identification and phylogenetic analysis of B3 superfamily in 12 species of angiosperms including roses.The results showed that REM family genes significantly increased in Rosaceae plants,especially in Rosa multiflora,and Rosa chinensis genotypes Old blush and Viridiflora,with 91,79 and 90 copies respectively.These results indicated that REM family genes played an important role in the evolution,growth and development of Rosa plants.2.In order to further identify the member information and subfamily classification of REM gene family in rose,we conducted phylogenetic analysis of REM genne family in rose for the first time,and predicted the physicochemical characteristics of proteins.The results showed that the REM gene family could be divided into six subfamilies,among which REM I and REM II subfamily were significantly expanded while REM V subfamily was widely lost in rose.These results indicated that the REM family genes in Rosa plants underwent extensive differentiation,and REM I and REM II subfamily genes played a critical role in the growth and development of rose.3.In order to explore the mechanism of significant expansion of REM family,we further carried out chromosomal localization and genome-wide collinearity analysis of REM family genes.The results showed that the significant expansion of REM family in rose mainly contributed to tandem duplication.In addition,collinearity analysis of the B3 superfamily genes in 12 representative angiosperms showed that tandem duplication was widespread in angiosperms.Moreover,compared with other gene families of B3 superfamily,tandem duplication emerged significant specificity of REM gene family.4.In order to further explore the biological functions of REM family genes in rose,we analyzed the expression patterns of the REM gene at different stages of flower bud differentiation and in different floral organ tissues by using Old Blush and its relative floral organ mutant Viridiflora.The results revealed that most of the REM genes were indeed specifically expressed in reproductive meristem and floral organs and their expression boundaries were dramatically changed along with the floral organ mutation in rose.These results suggested that REM family genes were important in rose flower development and may be involved in the boundary regulation of floral organ identity genes.5.In order to investigate the regulatory role of REM family genes in the process of flowering and flower development,we constructed a co-expression network of rose genes with REM gene as the center,and the genes related to flowering regulation,flower organ development,cell proliferation or cell expansion as the bias.The results showed that REM family genes were significantly co expressed with genes related to flowering regulation,floral organ development,cell proliferation or cell expansion,and the co expressed genes were significantly higher than the average level of the whole genome.These results further illustrated that REM gene family played a significant role in flowering regulation,floral organ development,cell proliferation or cell expansion.6.In order to further verify the function of REM family genes,this study screened the Rc REM18 gene for functional identification.The function of Rc REM18 gene was verified by over-expression in Arabidopsis thaliana and VIGS interference in Old blush.The results showed that over-expression of Rc REM18 in Arabidopsis resulted in bigger size of flower,and silencing Rc REM18 led to the smaller flowers.This indicated its prominent roles in regulation of flower size.7.In order to preliminarily explore the molecular mechanism of Rc REM18 regulating flower size in rose,the protein-protein interaction assay with ABCDE model genes showed that Rc REM18 could interacted with Rc AP1 and Rc AP2(A type)and Rc PI(B type).In addition,combined with the summary of the interaction between ABCDE model genes and flower size regulatory genes in the literature,we proposed a molecular model of Rc REM18 involved in regulating rose flower size.Taking together,our study provided new insights into the evolution of REM family genes in woody plants and their functions in flower organ development and growth,as well as enriches the regulation theory of plant flower size. |