Study On Key Genes Involved In Chlorogenic Acid Biosynthesis Of Pear Fruits Grown In Xinjiang Based On Transcriptomics

Xinjiang is an important pear producing area in China,and its planting area and yield are among the best in China.The famous cultivars include white pear system(Pyrus bretschneideri),sand pear system(P.pyrifolia),qiuzi pear system(P.ussuriensis)and P.sinkiangensis system unique to Xinjiang.Chlorogenic acid is the main characteristic polyphenol in pear fruits.In recent years,the development of RNA-Seq technology based on high-throughput sequencing has laid a foundation for studying the relationship between plant compound accumulation and key gene expression.In this study,Xinjiang characteristic pear(XCP)like“Yali”pear(YL),“Korla”fragrant pear(XL)and“Yuanhuang”pear(YH)were selected to study the developmental characteristics of pears at different developmental stages,analyze the differences of chlorogenic acid(CGA)content in pears at different developmental stages.Then the key enzyme genes of CGA biosynthesis pathway were explored by using De novo transcriptomics to provide theoretical basis for functional breeding of characteristic pear fruit in Xinjiang.1.Developmental characters,RNA extraction and sequencing analysis of XCPAccording to the variation trend of single fruit weight,58?88 days after full bloom(DAFB)was the young fruit stage,103?133 days was the expanding stage,148?163 days was the mature stage.The single fruit weight of YL,XL and YH at 163DAFB were 143.60 g,149.25 g and 254.70 g,respectively.The CGA contents in YL,XL and YH were 9560.62?g/g,6910.95?g/g and 1395.41?g/g at 58 DAFB in young fruit stage,and 2208.20?g/g,1037.20?g/g and 140.77?g/g at 163 DAFB in mature stage,respectively.Overall,the CGA content in YL was the highest,followed by XL,and YH was the lowest.In 27 RNA samples,the RNA concentration ranged from 50.6 ng/?L to 216.0ng/?L,the total RNA content ranged from 1.77?g to 7.56?g,the OD₂₆₀/OD₂₈₀ values were greater than 2.09,and the RIN values were greater than 9.5.A total of 1343719214clean reads were obtained from 27 RNA samples via RNA-seq and quality control.The total base number was 200.63 GB.The sequencing error rate was 0.0240%?0.0268%,and the percentage of Q30 was 92.4%?95.15%.In addition,CG%ranged from 46.35%to 50.02%,which indicated that the sequencing quality of each sample was excellent.2.Discovery of key enzyme genes in the CGA biosynthetic pathway in XLDe novo assembly was performed on 9 XL RNA samples of 88 DAFB(T1),103DAFB(T2)and 163 DAFB(T3)to obtain reference sequences.The average comparison rate of reference sequences for clean reads was 83.57%.The bioinformatics analysis of DEGs screened out 11 DEGs involved in the CGA biosynthesis in XL,including 1 PAL,2 C4H,3 4CL and 5 HCT.3.Discovery of CGA biosynthesis genes in XCP and gene co-expression analysis27 RNA samples of T1,T2 and T3 were De novo assembled to obtain reference sequences.The average comparison rate of clean reads was 73.42%.Bioinformatics analysis of DEGs among cultivars showed that 10 DEGs related to CGA biosynthesis existed in both T1 and T3 developmental stages,including 2 4CL,1 C4H,2 C3'H and5 HCT.WGCNA analysis of DEGs at T1 and T3 stages showed that 5 of 10 DEGs related to CGA biosynthesis were located in the green module,and other 2 DEGs were located in the pink module.The related DEGs in these modules may play an important role in CGA biosynthesis.