Transcriptional landscape illustrates the diversified adaptation of medicinal plants to multifactorial stress combinations linked with high altitude.

Abstract

Main conclusion: This study at high-altitude alpine environment reveals the molecular signatures associated with stress response and secondary metabolite accumulation, contributing to Picrorhiza kurroa adaptation, which is primarily regulated by a strong interplay of phytohormones. The high-altitude alpine environment is an extreme and variable environment with unique combinations of abiotic/biotic stresses. Despite progress about plant response to individual and combined abiotic stress in controlled conditions, our knowledge of plant adaptations to multifactorial stress combinations that typically occur in alpine environments is limiting. Here, we utilized the high-altitude medicinal herb Picrorhiza kurroa to investigate how multifactorial stress combinations prevailing along the high-altitude gradient at the western Himalayas affect gene expression and cellular pathways. Leaf transcriptional dynamics identified 7,388 differentially expressed unigenes (DEGs), highlighting unique gene expression patterns, specific pathways, and processes that play a crucial role in plant response to the complex micro-environment of high-altitude. Gene regulatory response largely relies on basic helix-loop-helix (bHLH), no apical meristem (NAC), and ethylene responsive factor (ERF) transcription factor families. Further, unigenes associated with secondary metabolism, multiple abiotic/biotic stress responses, and a variety of cellular and reproductive developmental processes were activated through complex cross-talk among plant hormonal signal transduction pathways. The weak correlation between gene expression and corresponding protein accumulation could predict stress-responsive protein abundance largely under different post-transcriptional/translational regulation. These findings recognize an array of new candidate genes for climate resilience, which would contribute to further our research on high-altitude alpine plant adaptations.