| Liquidambar formosana Hance.is an important afforestation and landscape tree in south China which is famous for its colored leaves in autumn.In recent enthusiam increased for breeding new plant varieties of Liquidambar formosana,however,there is still a certain gap between China and North America regarding the number of available varieties.The literature research of domestic and foreign varieties of Liquidambar formosana found that domestic variety breeding mainly focuses on leaf color variation.Purple and red leaves made up most of the varieties.Thus,we chose one variety from purple and one from the red group as the main research objects and analyzed the main reason of colored leaf variations from the difference of phenotypes and cell structures,differential metabolic,the key control genes and genetic relationships.The variety of ‘Fuluzifeng’ maintains its purple leaves in spring,summer and autumn,whereas the leaves of ‘Nanlinhong’ are red in spring and autumn,turn green in summer,and turn red again in autumn.Many research studies focus on leaf color in autumn.This study mainly focuses on leaf color in spring of two variety and leaf color variations within different seasons of ‘Nanlinhong’.It was found that the main reason for seasonal leaf color changes was environmental factors.The leaf maitain purple in summer because of genetic variation.The main conclusions of this study can be divided into the following four points:1.Cell structure.The differences of pigment distribution and cell structure among four colored leaves were observed by means of freehand section,paraffin section and ultramicroscopy.It was found that the leaf cell structure of ‘Fuluzifeng’ was more compact and pigment was more widely distributed in mesophyll cells.2.Metabolism composition.Colorimetric method and high performance liquid chromatography were used to compare the differences of pigment components and contents in four different colored leaves.It was found that anthocyanins were the main pigment component in purple and red leaves,while carotenoid was the main color component in yellow leaves,which was affected by temperature.Then,the flavonoids metabolites in red leaves with three seasons and the purple leaves were analyzed qualitatively and quantitatively by means of large-scale metabolism.It was found that the main anthocyanin components of ‘nanlinghong’were peonidins and cyanidins,and the red leaves in spring and summer were due to the high content of anthocyanins.The different colors because of the different ratio of pigment composition.Photoperiod is the main factor affecting the seasonal variation of leaf color.The main anthocyanins of ‘Fuluzifeng’ can be divided into five types,including cyanidins,peonidins,delphinidins,pelargonidins and malvidins,and the concentrations of the five kind of anthocyanins were similar.Delphinidins and pelargonidins are the main reason for appearance of the purple leaves.3.Candidate key genes.The transcriptome and metabolome were used for a joint differential analyses on the anthocyanidin synthesis pathways of ’Nanlinghong’ and ’Fuluzifeng’.The q RT-PCRs were used to compare the differences of key gene expression level between the two variety leaves and the season leaves of ‘Nanlinhong’.The results showed that the Lf F3’5’H gene was the main reason for the significant accumulation of delphinidins in the spring leaves of ‘Fuluzifeng’.The seasonal changes of leaf color may be co-regulated by transcription factors of Lf MYBS3,Lf MYBC,Lfb HLH48 and Lfb HLH63.Lf MYBS1 play the key role on the purple leaves of ‘Fuluzifeng’ in summer.4.Genetic difference.The DFR gene between ‘Fuluzifeng’ and ‘Nanlinghong’ had an amino acid mutation by using protein homology analyses.It indicated the reason of accumulation of pelargonidins in the spring and summer leaves of ‘Fuluzifeng’.Genetic relationship between the two varieties was analyzed by SSR markers.The result showed a far relationship between two varieties,while the relationship between ‘Fuluzifeng’ and a sample of Liquidambar acalycina was closer.Therefore,the chloroplast genome of ‘Fuluzifeng’ was used for genetic analyses among 30 species.The results showed that it might be a hybrid or a varietas of L.acalycina.It was proved that the reason for the purple leaves in summer was genetic variation.This study analyzed the key factors of color leaf variation of Liquidambar from physiological differences to molecular analysis,and laid a theoretical foundation for the breeding of new plant variety of Liquidambar. |
