Study Of Petal Loss Related Genes And Sexual Differential Associated Metabolites In Litchi

Litchi(Litchi chinensis Sonn.)has an apetalous attribute,whereas longan,from the Sapindaceae Family,has typical petal.Thus,‘Feizixiao' litchi and ‘Chuliang' longan were used as comparative materials,and the genes belong to ABCDE model were targeted to study the molecular mechanism,according to the analysis of gene expression,protein-DNA interaction and promoter.Additionally,the metabolites in leaves from the plants that firstly formed male flowers and the plants that firstly formed female flowers were analyzed using non-targeted metabolome measurement.The main results are as follow:(1)There were 16 genes from ABCDE model identified in litchi,including LcAP1,LcAP2-1 and LcAP2-2(A group),LcAP3-1,LcAP3-2 and LcPI(B group);LcAG(C group);LcSTK1,LcSTK2,LcSTK3 and LcSTK4(C group),LcSEP1,LcSEP2,LcSEP3,LcSEP4 and LcSEP5(E group).All genes except for AP2 are belong to MICK sub-family in MADS-Box super family,which contain highly conserved MADS and K domains and diverse I and C domains.(2)The petal formation is mainly regulated by genes in ABE group.The expression of above genes from male and female flowers at different stages were analyzed.The expression of A group genes like LcAP1 and LcAP2-1 decreased during litchi flower development,and the expression of AP1 and AP2-1 genes were much higher in longan male flower in comparison with litchi male flower.LcAP3-1,B group gene,also decreased during the litchi flower development,but showed relative lower expression in longan,which needs to be furtherly investigated.For E group genes,the expression of LcSEP3 and LcSEP5 significantly decreased during litchi flower development,and the expression of LcSEP4 was much higher in longan when compared to litchi.Thus,it is suggested the involvement of LcAP1,LcAP2-1,LcAP3-1,LcSEP3,LcSEP4 and LcSEP5 in litchi apetalous attribute.(3)To investigate that if the petal loss in litchi resulted from the insufficient interactions between ABE genes,transient co-expression in tobacco leaves was applied to study protein-DNA interaction.As results,LcAP3-1 and LcSEP5 accordingly activated the activity of the promoter of LcSEP5 and LcAP2-1,and LcAP2-1 repressed the promoter of LcAP3-1.(4)For the promoter of LcAP3-1 was furtherly investigated.According to the alignment of promoter sequences of LcAP3-1 and DlAP3-1,the similarity in nucleotide and amino acid sequences of them is 82.7% and 99.1%,respectively.The great difference in protein structure of the two homologues indicated the diversity in functions.(5)The metabolome in leaves from the plants that firstly formed male flowers and the plants that firstly formed female flowers were measured and analyzed.As results,the differential metabolites of each group were significantly enriched into glycerophospholipid metabolism.In the development process of plants that started with female flowers,the content of quinic acid,alpha-linolenic acid,coproporphyrin and kaempferol phenol decreased obviously,and the content of astaxanthin,cholestane,choline increased obviously in leaves.In the development process of plants that started with male flowers,the content of canthaxanthin,adonixanthin,guanidinobutanoic acid declined obviously,and the content of rosemary acid increased obviously.At the "white spots" stage,the content of thiamin pyrophosphate and arginine in the plant that started with male flowers were significantly higher than that of the plants that started with male flowers,and the content of faniol showed opposite pattern.At the late "white spots" stage,the content of methylimidazoleacetic acid and arginine in the plant that started with male flowers were significantly higher than that of the plants that started with male flowers,and the content of farnesol showed opposite pattern.