Tissue specific de novo transcriptome sequencing and expression analysis of candidate genes for terpenoid biosynthesis in Piper longum.

Piper longum L. an economically important plant lacks adequate molecular resources towards unmasking molecular mechanisms for terpenoid biosynthesis. The transcriptome profiling generated 36.91 and 36.24 million raw reads in leaf and fruit tissue respectively. The de novo transcriptome assembly was performed with 36,688,460 and 36,011,305 clean reads, which subsequently produced 40,033 and 44,025 coding sequences (CDS) in leaf and fruit samples, respectively. The CDS were annotated using different databases such as Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). These annotations resulted mining of various trait specific genes including important terpenoid biosynthesis genes. Presence of 53 and 58 terpenoid compounds in essential oils of leaf and fruit of long pepper have also been identified using GC-MS. Additionally, relative gene expression of eight terpenoid biosynthesis genes each for both leaf and fruit were conducted using real-time polymerase chain reaction (RT-PCR). For further genetic diversity study, 4085 and 4564 number of SSRs were identified in leaf and fruit, respectively. This study significantly contributes to the understanding of long pepper at the molecular level by expanding the available genetic resources. This paves the way to improve long pepper varieties and develop new genotype with desirable quality traits.