Functional Analysis Of A Flavonoad Glycosyltransferase Gene LGP And A Flower Developmental Gene CALLI In Medicago Truncatula

Flavonoids are secondary metabolities and widely distributed throughout the plant kingdom,involving in numerous physiological process,including signal transduction,response to stress,regulation of auxin transportation.Glycostransferases modify flavonoids and change their properties of biological activity and chemical stability.Through forward genetic screening,we have isolated four mutants with semi-dwarf phenotype from Medicago truncatula Mutant Database.These mutant lines exhibited reduction in the content of anthocyanin,down-curved leaves in addition to its semi-dwarf stature.A gene,LIMONOID UDP-GLUCOSYLTRANSFERASE-LIKE PROTEIN,co-segregates with the Tntl retrotransposon insertion in these mutant lines.We named the gene LGP for short.The expression of LGP was interrupted in Igp,as determined by RT-PCR.Overexpression of LGP rescued the developmental defects and recovered the anthocyanin content inlgp mutant,indicating that LGP was responsible for structure development and anthocyanin synthesis in Medicago.To study the expression pattern of LGP,we constructed the transformed line proLGP::GUS,and found LGP expressed in leaves specially.The recombination protein LGP-GST could catalyze the glycosylation of flavones and flavonols by using UDP-glucose as sugar donor,but anthocyanins.We measured the components and contents of flavonoid in mutants by HPLC.The data showed that flavonoid construct and level were significantly different from the control.We also found that Igp showed different pattern of nodule development.The datas suggested that LGP plays a role of flavonoid glycpstransferase,involved in the flavonoid biosynthesis,and affected the plant developmental progress in addition to the leaf development.Flower is the reproductive organ of the plant.The model plant Medicago truncatula had five sepals,five petals,ten stamens and one carpel.Research on the flower of Medicago truncatula will offer an opportunity to study the fertility of flower and increase the production of herbage.We screened the Medicago truncatula Mutant Database,and some mutants with abnormal flower in which stamens and carpel transformed into endless irregular petals were obtained.As the appearance of the mutants' flower was like a cauliflower,we named these mutants as calli.The gene contains a MYB-like DNA binding domain.Overexpression of CALLI rescued the flower developmental defect in calli CALLI-GFP was a nucleus-localized transcription factor.To study the expression pattern of CALLI,we constructed the transformed line proCALLI::GUS,and found that CALLI was highly expressed in the flower tissue.In order to study the developmental progress of flower in mutant,we observed the floral organ primordia using scanning electron microscopy,and found that the progress changed in mutant.The stamen primordia and carpel primordia were absent.The flower contains irregular petal primordia and sepal primordia in calli compared with the wild type during developmental stages.To explore the function of CALLI in flower development,we examined the expression levels of the floral genes in calli flowers,and found that the genes involved in A and B functions were up-regulated,while the genes involved in C function were down-regulated.To learn the relationship between CALLI and ABC genes,we also generated and analyzed double mutants,and found that CALLI was responsible for flower development,cooperated with ABC genes.These results suggested that CALLI was a MYB-like transcription factor and responsible for development of stamens and carpel in Medicago truncatula in the floral identity specification.