Cloning And Functional Study Of Four Flowering Time Related Genes In Litchi Chinensis Sonn.

Litchi(Litchi chinensis Sonn.),a kind of specially commercial fruits in the south of China,is favored by consumers because of the nutrition and excellent quality.The prerequisite for high and stable production of litchi is accurately regulating the early flower bud differentiation.The research on the molecular mechanism in different flowering pathways of litchi could provide theoretical foundation about its flower buds division.There were few reports about the photoperiodic flowering pathway of litchi,however,the key gene in the flowering pathway,CONSTANS(CO),has been deeply studied in other species such as chrysanthemum,rice,and loguat.So the key factor Lc CO was studied.The early-flowering litchi ‘Sanyuehong' seedlings were used as plant materials to explore the relationship between light hours and flowering.The q RT-PCR was used to analysis the expression and circadian rhythm of the other genes such as Lc FT1,Lc CO,Lc GI,Lc SOC1-1 and Lc FD.Secondly,the function of Lc CO,Lc SOC1-1,Lc FD and Lc GI were initially verified by transformation of Arabidopsis.Dual luciferase reporter gene detection system was.The effects of the transcription activation of the transcription factor Lc GI,Lc CDF3,Lc ELF3 and Lc FKF1 to Lc CO,and that of the Lc CO to Lc FT1 and Lc SOC1-1 were studied.The results are as follows:(1)There was no difference of flowering time between the normal light and full-day light treated trees.However,the proportion of male and female flowers in ND was higher than that in FD.The expression of Lc FT1?Lc CO and Lc GI gradually increased during the flowering procedure,furthermore the expression of those genes in ND was higher than that in FD.The expression of Lc SOC1-1 and Lc FD were stable,but Lc FT1,Lc CO and Lc GI had a circadian rhythm.It was found that Lc FT1 expression increased during the day and decreased at night,while Lc CO had a completely reversed expression pattern.(2)Over-expression of Lc CO,Lc SOC1,Lc FD,and Lc GI in Arabidopsis leaded to early flower.The transgenic plants have fewer rosette leaves than wild type,suggesting that there function was conservative and could promote flowering.(3)Using the dual-luciferase transient expression assay,it was found that the LUC/REN value of Lc ELF3 was much lower than control,indicating that Lc ELF3 transcription factor might act as a transcription repressor of Lc CO.While the LUC/REN value of Lc CO was significantly higher than that control,indicating that Lc CO could activate the promoter activities of Lc FT1.Transcription factor Lc GI,Lc CDF3 and Lc FKF1 have no effect on Lc CO promoter,and the transcription factor Lc CO has no effect on Lc SOC1-1.