Mining of starch-degrading related genes in red-fleshed dragon fruit and expression analysis based on transcriptome sequencing

【Objective】 To explore genes related to starch degradation in red-fleshed dragon fruit and analyze their expression patterns at different developmental stages of the fruit,which could provide theoretical basis for elucidating the starch degradation pathway in the ripening process of red-fleshed dragon fruit.【Method】The tested red-fleshed dragon fruit variety was Ruanzhidahong.Four different developmental stages （19 d after flowering,22 d after flowering,25 d af‐ter flowering and 28 d after flowering） were selected for transcriptomic sequencing,and the Fold Change≥2 and error discovery rate （FDR）＜0.01 were used as the standard.Differentially expressed genes （DEGs） in fruits at different developmental stages were screened for GO functional annotation and KEGG signaling pathway enrichment analysis.Realtime fluorescence quantitative PCR was used to verify the reliability of transcriptome sequencing data and analyze the ex‐pression patterns of candidate genes. 【Result】 A total of 22.84 Gb of clean data were obtained by transcriptome sequencing,with 76618317 clean reads,GC content of 44.78%-46.83%and Q20 ranging from 98.89%-99.74%,Q30 ranging from 96.73%to 98.53%.Compared with 19 d after flowering,there were 4194 DEGs on 28 d after flowering,of which1728 were up-regulated and 2466 were down-regulated.The results of GO functional annotation analysis showed that the DEGs annotation in the comparison group at 28 d after flowering and 19 d after flowering were classified into 3 catego‐ries:biological processes,cell components and molecular functions.In biological processes,the number of DEGs in‐volved in cellular processes was the largest,followed by metabolic processes.The results of KEGG signaling pathway en‐richment analysis showed that DEGs of the comparison group at 28 d after flowering and 19 d after flowering were signifi‐cantly enriched in starch and sucrose metabolic pathways.Ten genes related to starch and sucrose metabolic pathways were screened,including glucan water dikinase （GWD） gene （HU02G00177）,phosphoglucan water dikinase （PWD） gene （HU09G02021）,phosphoglucan phosphatase （SEX） gene （HU07G01227）,β-amylase （BAM） gene （HU10G00833,HU10G00777）,α-amylase （AMY） gene （HU05G01323,HU02G00293,HU02G01323）,isoamylase （ISA） gene（HU11G01417）,and disproportionating enzyme （DPE） gene （HU09G01260）.Real-time fluorescence quantitative PCR showed that the expression trend of 10 starch degrading genes was consistent with the transcriptome sequencing data.Rela‐tive expression levels of HU02G00177,HU07G01227,HU10G00833,HU10G00777,HU02G00293 and HU11G01417genes in the later stages of fruit development was higher than the early stage of fruit development. 【Conclusion】 The expression patterns of genes related to starch degradation in red-fleshed dragon fruit are different at different developmental stages.Among them,GWD gene （HU02G00177）,SEX gene （HU07G01227）,BAM gene （HU10G00833,HU10G00777）,AMY gene （HU02G00293）,ISA gene （HU11G01417） may play an important role in the later stage of fruit development.