AUTHOR=Qingzhu Hua , Chengjie Chen , Zhe Chen , Pengkun Chen , Yuewen Ma , Jingyu Wu , Jian Zheng , Guibing Hu , Jietang Zhao , Yonghua Qin 

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

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.01179

DOI=10.3389/fpls.2015.01179

ISSN=1664-462X

ABSTRACT=<p>Betalains have high nutritional value and bioactivities. Red pulp pitaya (<italic>Hylocereus polyrhizus</italic>) is the only fruit containing abundant betalains for consumer. However, no information is available about genes involved in betalain biosynthesis in <italic>H. polyrhizus</italic>. Herein, two cDNA libraries of pitaya pulps with two different coloration stages (white and red pulp stages) of Guanhuahong (<italic>H. polyrhizus</italic>) were constructed. A total of about 12 Gb raw RNA-Seq data was generated and was <italic>de novo</italic> 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 <italic>H. polyrhizus</italic> (7-1) and <italic>H. undatus</italic> (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.</p>