Dwarfing is a pivotal agronomic trait affecting both yield and quality.Citrus species exhibit substantial variation in plant height,among which internode length is a core element.However,the molecular mechanism govern...Dwarfing is a pivotal agronomic trait affecting both yield and quality.Citrus species exhibit substantial variation in plant height,among which internode length is a core element.However,the molecular mechanism governing internode elongation remains unclear.Here,we unveiled that the transcriptional cascade consisting of B-BOX DOMAIN PROTEIN 22(BBX22)and ELONGATED HYPOCOTYL 5(HY5)finely tunes plant height and internode elongation in citrus.Loss-of-function mutations of BBX22 in an early-flowering citrus(Citrus hindsii“SJG”)promoted internode elongation and reduced pigment accumulation,whereas ectopic expression of BBX22 in SJG,sweet orange(C.sinensis),pomelo(C.maxima)or heterologous expression of BBX22 in tomato(Solanum lycopersicum)significantly decreased internode length.Furthermore,exogenous application of gibberellin A3(GA3)rescued the shortened internode and dwarf phenotype caused by BBX22overexpression.Additional experiments revealed that BBX22 played a dual role in regulation internode elongation and pigmentation in citrus.On the one hand,it directly bound to and activated the expression of HY5,GA metabolism gene(GA2 OXIDASE 8,GA2ox8),carotenoid biosynthesis gene(PHYTOENE SYNTHASE 1,PSY1)and anthocyanin regulatory gene(Ruby1,a MYB DOMAIN PROTEIN).On the other hand,it acted as a cofactor of HY5,enhancing the ability of HY5 to regulate target genes expression.Together,our results reveal the critical role of the transcriptional cascade consisting of BBX22 and HY5 in controlling internode elongation and pigment accumulation in citrus.Unraveling the crosstalk regulatory mechanism between internode elongation and fruit pigmentation provides key genes for breeding of novel types with both dwarf and health-beneficial fortification in citrus.展开更多
基金supported by funding from the National Natural Science Foundation of China granted to Q.X.(number 31925034)the National Key Research and Development Program of China granted to Q.X.(number 2022YFF1003100)+3 种基金Major Special Projects and Key R&D Projects in Yunnan Province granted to Q.X.(202102AE090054)the Key Research and Development Program of Hubei granted to X.W.(number 2022BBA155)the Foundation of Hubei Hongshan Laboratory granted to Q.X.(number 2021hszd016)Key Project of Hubei Provincial Natural Science Foundation granted to Q.X.(number 2021CFA017)。
文摘Dwarfing is a pivotal agronomic trait affecting both yield and quality.Citrus species exhibit substantial variation in plant height,among which internode length is a core element.However,the molecular mechanism governing internode elongation remains unclear.Here,we unveiled that the transcriptional cascade consisting of B-BOX DOMAIN PROTEIN 22(BBX22)and ELONGATED HYPOCOTYL 5(HY5)finely tunes plant height and internode elongation in citrus.Loss-of-function mutations of BBX22 in an early-flowering citrus(Citrus hindsii“SJG”)promoted internode elongation and reduced pigment accumulation,whereas ectopic expression of BBX22 in SJG,sweet orange(C.sinensis),pomelo(C.maxima)or heterologous expression of BBX22 in tomato(Solanum lycopersicum)significantly decreased internode length.Furthermore,exogenous application of gibberellin A3(GA3)rescued the shortened internode and dwarf phenotype caused by BBX22overexpression.Additional experiments revealed that BBX22 played a dual role in regulation internode elongation and pigmentation in citrus.On the one hand,it directly bound to and activated the expression of HY5,GA metabolism gene(GA2 OXIDASE 8,GA2ox8),carotenoid biosynthesis gene(PHYTOENE SYNTHASE 1,PSY1)and anthocyanin regulatory gene(Ruby1,a MYB DOMAIN PROTEIN).On the other hand,it acted as a cofactor of HY5,enhancing the ability of HY5 to regulate target genes expression.Together,our results reveal the critical role of the transcriptional cascade consisting of BBX22 and HY5 in controlling internode elongation and pigment accumulation in citrus.Unraveling the crosstalk regulatory mechanism between internode elongation and fruit pigmentation provides key genes for breeding of novel types with both dwarf and health-beneficial fortification in citrus.
