Study On The Changes Of Anthocyanins And The Differential Expression Of Related Genes During The Development Of ’Meihong’ Strawberry Petals

In this study,the red-flowered strawberry variety’Meihong’was used as the research material to observe the difference in the number of flower organs and the change of flower color phenotype during the development of flowers.We determined the pigment content in the petals of different developmental stages,and performed transcriptome sequencing on the petals of the four developmental stages to analyze the gene expression differences in strawberry flowers at different developmental stages and to select structural genes and regulatory genes related to anthocyanin biosynthesis at different developmental stages of strawberry flowers,and then we performed qRT-PCR verification on the expression patterns of these differential genes,the main findings as follows:1.’Meihong’strawberry was a strawberry variety with greater ornamental and edible value.The number of petals on’Meihong’strawberry varied greatly and has the potential to form double-petalled flowers.The number of petals of’Meihong’strawberry flowers was mainly 5,6 and 7;The number of sepals was mainly 10,11 and 12;The number of stamens was mainly between 20 and 30;There was a significant positive correlation between the number of sepals;The corolla diameter of the single flower was mainly concentrated between 20 and 30mm,and there was no correlation between the number of petals and the size of the corolla diameter;Most of the flower petals were overlapping;When the’Meihong’strawberry buds were 4 mm in size(the petals have not been colored),it only took another 6 days to fully expand the petals,and the flowers were fully bloomed.When the flowers were fully bloomed,the petals a~*were mainly distributed between 55.00～60.00;b~*were mainly distributed between 0.00～10.00;C~*were mainly distributed between 55.00～62.50;The C~*was mainly contributed by a~*.2.The accumulation of anthocyanins was the reason why the petal color of’Meihong’strawberry turns red.From buds to the half-expanded state of the petals,the content of anthocyanins in the petals continued to accumulate.When the flowers were fully bloomed,the anthocyanins in the petals were degraded and the content was reduced.By mass spectrometry analysis,two anthocyanin substances containing cyanidin-3-O-glucoside and pelargonidin-3-O-glucoside were identified in the petals.3.Transcriptome sequencing was performed on petals of four developmental stages(S1,S2,S3,and S6).The clean reads of all samples were more than 99.83%,and the effective reads were above 98.42%.The comparison rates with the reference genome(Fragaria x ananassa Camarosa Genome Assembly v1.0.a1)were all above 89%.Trend analysis of differential genes,a total of 34036 trend genes were obtained;7512 differential trend genes were annotated to the KEGG databases,of which 94 genes were involved in flavonoid biosynthesis and 6 genes(i.e.maker-Fvb7-1-augustus-gene-319.41,maker-Fvb7-4-augustus-gene-3.55,maker-Fvb7-2-snap-gene-316.69,maker-Fvb7-3-augustus-gene-14.53,maker-Fvb7-2-snap-gene-279.55 and maker-Fvb7-4-snap-gene-17.52)were involved in anthocyanin biosynthesis.From the differential trend genes,124 differential structural genes related to anthocyanin synthesis pathway(including genes related to modification and transport)can be identified,and 109 R2R3-MYB and 148 b HLH differential genes were also identified at the same time.This study selected 6 R2R3-MYB(i.e.Fa MYB82、Fa MYB6、Fa MYB90、Fa MYB305-1、Fa MYB305-2 and Fa MYB305-3)and 2 b HLH(i.e.Fab HLH35 and Fab HLH94)transcription factors that may be involved in anthocyanin synthesis.Phylogenetic tree analysis of 6 R2R3-MYB and 2 b HLH transcription factors revealed that they were aggregated with related transcription factors involved in anthocyanin regulation,such as Arabidopsis,indicating that these genes are highly likely to participate in anthocyanins biosynthesis.4.The qRT-PCR results showed that the relative expression levels of the 10 structural genes and 8 regulatory genes related to anthocyanin synthesis in the petals of’Meihong’strawberry were basically consistent with the changes in the expression levels obtained by transcriptome sequencing.4 structural genes(i.e.Fa4CL-1,Fa4CL-2 and Fa DFR and Fa3GT)had a strong positive correlation with anthocyanin content.Five R2R3-MYB(i.e.Fa MYB6,Fa MYB305-1,Fa MYB305-2,Fa MYB305-3 and Fa MYB90)and one b HLH(i.e.Fab HLH94)had significant positive correlation with the anthocyanin content,and had very significant positive correlation with the structural genes Fa PAL,Fa4CL,Fa DFR,and Fa3GT;The other two transcription factors(i.e.Fa MYB82 and Fab HLH35)were negatively correlated with anthocyanin content,and were significantly and strongly negatively correlated with Fa PAL,Fa4CL,Fa DFR,and Fa3GT.These results indicated that the selected eight transcription factors may affect the synthesis of anthocyanin in strawberry petals by regulating the expression of Fa PAL,Fa4CL,Fa DFR,and Fa3GT.