Hu GuiBing

Transcriptomic Analysis Reveals Key Genes Related to Betalain Biosynthesis in Pulp Coloration of Hylocereus polyrhizus

Betalains have high nutritional value and bioactivities. Red pulp pitaya (Hylocereus polyrhizus) is the only fruit containing abundant betalains for consumer. However, no information is available about genes involved in betalain biosynthesis in H. polyrhizus. Herein, two cDNA libraries of pitaya pulps with two different coloration stages (white and red pulp stages) of Guanhuahong (H. polyrhizus) were constructed. A total of about 12 Gb raw RNA-Seq data was generated and was de novo assembled into 122,677 transcripts with an average length of 1183 bp and an N50 value of 2008. Approximately 99.99% of all transcripts were annotated based on seven public databases. A total of 8871 transcripts were significantly regulated. Thirty-three candidate transcripts related to betalain biosynthesis were obtained from the transcriptome data. Transcripts encoding enzymes involved in betalain biosynthesis were analyzed using RT-qPCR at the whole pulp coloration stages of H. polyrhizus (7-1) and H. undatus (132-4). Nine key transcripts of betalain biosynthesis were identified. They were assigned to four kinds of genes in betalain biosynthetic pathway, including tyrosinase, 4, 5-DOPA dioxygenase extradiol, cytochrome P450 and glucosyltransferase. Ultimately, a preliminary betalain biosynthetic pathway for pitaya was proposed based on betalain analyses, gene expression profiles and published documents.

Molecular marker analysis of ‘Shatangju’ and ‘Wuzishatangju’ mandarin ( Citrus reticulata Blanco )

‘Wuzishatangju’( Citrus reticulata Blanco ) is an excellent cultivar derived from a bud sport of a seedy ‘Shatangju’ cultivar found in Guangdong Province in the 1980s. In this study, six molecular markers including random amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR), simple sequence repeat (SSR), sequence-related amplified polymorphism (SRAP), inter-retrotransposn amplified polymorphism (IRAP) and retrotransposon-microsatellite amplified polymorphism (REMAP) were used to study the genetic variations between ‘Shatangju’ and ‘Wuzishatangju’. 1196 RAPD, seven SSR, 28 IRAP and 56 REMAP primers were used to detect the genetic variations between ‘Shatangju’ and ‘Wuzishatangju’. However, no difference was observed between the two cultivars. These results indicate that there was a very close genetic relationship between ‘Shatangju’ and ‘Wuzishatangju’ and RAPD, SSR, IRAP and REMAP markers could not distinguish them. Two and 21 specific bands were obtained using 100 ISSR and 153 SRAP primers, respectively. The present research could be a valuable tool for identification of Citrus bud sport clones, which laid the foundations for the further study of the mechanisms of Citrus bud sports. Key words : Citrus reticulata Blanco, random amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR), simple sequence repeat (SSR), sequence-related amplified polymorphism (SRAP), inter-retrotransposon amplified polymorphism (IRAP), retrotransposon-microsatellite amplified polymorphism (REMAP), identification.