YS Sew1, J Baharom 1, M Yaakob 2 and Z Meon 2
1Biotechnology Research Centre, 2Station Management Centre,
Malaysian Agricultural Research and Development Research Institute
MARDI Headquarters, 43400 Serdang, Selangor D.E., Malaysia
Pitayas had gained much interest in society because of its exotic features, attractive colour, nutritional value and pleasant taste. Phenolic compounds and high phytoalbumin antioxidants value of pitayas are believed to prevent the formation of cancer-causing free radicals. However, research on the molecular studies of pitayas is very lacking and gene information of pitayas particularly in regards to their health benefit phyto-chemicals deposited in the public databases is extremely limited. With the aim to enrich genes information and identify genes that associated with secondary metabolism of red pitaya, we have carried out transcriptome study on a local variety of red pitaya (Hylocereus polyrhizus).
Red pitayas were collected from MARDI Kundang Station with different ripening index. Total RNA of red pitaya fruits with 35 days after anthesis (DAA) were extracted and purified to get high quality total RNA. The purified total RNA was then subjected to Solexa sequencing using paired-end mRNA-seq method. The mRNA-seq sequencing results showed that total number of red pitaya paired-end reads obtained was 18,530,028 sequences and total number nucleotides obtained was 1,389,752,100nt. Sequence assembly using Velvet software revealed a total of 106,867 nodes. After the sequence filtering process (set value as >80bp/node), we obtained 62,333 nodes. The homology search on the filtered sequences against non-redundant nucleic acid database (NR) showed that 31,423 nodes with significant E-value≤10-5. It was found that there were at least 97 nodes mapped to secondary metabolic pathways via Blast2Go analysis, particularly the biosynthesis pathways of phenylproparoid, betalain, flavonoid, carotenoid and monoterpenoid.
The identification of genes involved in secondary metabolism and their corresponding biochemical pathways will enable us in harnessing the potential of red pitaya as functional food with optimal level of beneficial phyto-chemicals and also to control the production of those phyto-nutrients through genetic manipulation.