Functional Analysis Of Floral Genes SOC1,SVP And LFY In Prunus Mume

Mei(Prunus mume)belonging to Rosaceae family,is a well-known and traditional Chinese flower with high ornamental value and rich cultural connotations.Compared with other Prunus species,mei can flower in early spring in south of the Yangtze river region.The flowering period of mei is important horticultural and cultivated characters.Flowering transition is a qualitative change in the life cycle of higher plants and an important turning point in the transition from vegetative to reproductive growth.Previous studies have shown that SOC1,SVP,LFY,and other flowering-integron genes play an important regulatory role in the processes of flowering transition.These genes have been isolated from many plants and studied in depth.However,floral genes of mei have been rarely reported.For these reasons,seven floral genes from mei were cloned by RT-PCR.Their expression patterns were determined by quantitative RT-PCR.Yeast two-hybrid system was used to study the protein interaction models of these genes.All these results together with the phenotype changes in Arabidopsis overexpressing these genes were used to elucidate the roles of these genes.The main results are as follows:1.RT-PCR was used to clone seven floral genes from mei.Among these genes,three were SOC1 homologous genes;two of them were SVP homologous genes,and the remaining two genes were LFY homologous genes.PmSOC1s gene and PmSVP1s gene belong to the SOC1/TM3 and STMADS11 subfamily of the MADS-box family,respectively.Two PmLFYs genes had high homology to their orthologous genes,suggesting that PmLFYs genes had high conservation as a flowering-related gene.However,unlike the single copy form of LFY gene in most of the diploid species,mei had two LFY homologous genes,indicating that PmLFYs genes underwent species-specific evaluation in mei.2.Expression analysis showed that PmSOC1s and PmSVPs genes were mainly expressed in vegetative organs,and almost completely unexpressed in reproductive organs.PmLFY1 gene was strongly expressed in pistil and seeds and also expressed in vegetative organs but with low expression levels,suggesting that they might be involved in the development of the ovules and seeds.Unlike the expression patterns in the adult trees of mei,PmSOC1-2 and PmLFY1 genes were not expressed in seedling stage,which might be one of the reasons why mei does not flower during juvenility.PmSOCIs and PmSVPs genes were generally down-regulated during the flower bud differentiation process,suggesting that they might play an important role in flowering transition in mei.PmLFY1 was highly expressed in the late stage rather than the early stage of flower bud differentiation in mei,suggesting that PmLFY1 might play a regulatory role in flower differentiation after flower primordium formation.3.The results of the interaction patterns showed that PmSOC1-1 and PmSOC1-2 had similar protein-protein interactions and both had strong interactions with PmSVP1 and PmAP1.PmSOC1-3 had no interaction with any of the detected proteins.PmSVP1 interacted with some genes but except PmSOC1-3.PmSVP2 only interacted with PmSVP1.In addition to its strong interaction,PmAP1 also interacted with PmSOC1-1,PmSOC1-2,and PmSVPl.Through the comprehensive analysis of gene expression and protein-protein interaction patterns,suggesting that PmSVP1 might interact with PMSOC1-1 and PmSOC1-2 in the vegetative organs or flower buds that are about to differentiate to inhibit the transition to flowering.Interactions between PmAP1 and PmSOC1-1,PmSOC1-2,and PmSVP1 genes might take place in mei flower buds that are about to differentiate or were differentiating.4.Seven floral genes of mei were overexpressed in Arabidopsis.Three PmSOC1s genes promoted flowering and affected the development of flower organs.PmSVPl delayed flowering and maintained vegetative growth and inhibited flowering transition.Whereas PmSVP1 could not delayed flowering but can promoted inflorescence branching.PmLFYs gene had the ability to advance flowering and convert the inflorescence meristem to flower meristem.However,the effect of PmLFY2 was weaker than that of PmLFY1.Together with the expression pattern analysis of these two genes,PmLFYs genes were not only limited to regulate flowering transition but may also play a role in all stage of inflorescence and flower development.In this study,seven floral genes were investigated first then the functions of genes related to flower transition were explored.The results of this study will help elucidate the molecular mechanisms involved in the transition from vegetative to reproductive development in mei,and will provide an effective and practical way to study flower transition of mei by molecular methods.