Comparative transcriptome and metabolme analysis reveals the molecular insights of multiple stress tolerance in Citrus aurantifolia overexpressing a novel trypsin inhibitor from Putranjiva roxburghii

Being a sessile organism, plants are constantly confronted by various biotic (pest and pathogen) and abiotic (drought, salinity, flood, extreme temperatures, etc.) stresses. In response to these environmental stresses, plants have developed numerous defense mechanisms. One of the basal defense responses in plants are mediated by trypsin inhibitors (TIs). Putranjiva roxburghii trypsin inhibitor (PRTI), a potent trypsin inhibitor from P. roxburghii showing sequence similarity with a group of genes known to have defense and storage function such as wound inducible (WIN) proteins, vegetative storage proteins (VSPs), and Bark storage protein (BSPs) was overexpressed in Citrus aurantifolia. PRTI overexpressing lines were tolerant to various abiotic stresses (salinity, drought, and alkalinity) and two pests namely, Scirtothrips citri and Papilio demoleus. The molecular insights underlying the heterologous overexpression of PRTI at the transcriptomic level reveals the upregulation of stress responsive genes and involvement of hormonal signal transduction and transporters. Further, genes related to DNA repair, amino acid synthesis, and development were also found to be upregulated. Our study also reveals the nuclear-cytoplasmic localization and alteration phytohormone profile by PRTI overexpression in transgenic lines as compared to wild-type which clearly indicates the role of abscisic acid ABA in stress tolerance. Comparative gene expression profiling analysis of RNA-seq data for Citrus aurantifolia wild type and transgenic overexpressing a novel trypsin inhibitor from Putranjiva roxburghii.