Transcriptome and metabolome analysis reveal candidate genes and biochemicals involved in tea geometrid defense in Camellia sinensis.

Wei-Wei Wang,Chun-Lei Ma,Wan-Jun Hao,Liang Chen,Chao Zheng,De-Jiang Ni,Jian-Qiang Ma,Tapan Kumar Mondal

doi:10.1371/journal.pone.0201670

Abstract

Tea plant (Camellia sinensis (L) O. Kuntze) respond to herbivore attack through large changes in defense related metabolism and gene expression. Ectropis oblique (Prout) is one of the most devastating insects that feed on tea leaves and tender buds, which can cause severe production loss and deteriorate the quality of tea. To elucidate the biochemicals and molecular mechanism of defense against tea geometrid (TG), transcriptome and metabolome of TG interaction with susceptible (SG) and resistance (RG) tea genotypes were analyzed by using UPLC-Q-TOF-MS, GC-MS, and RNA-seq technologies. This revealed that jasmonic acid was highly induced in RG, following a plethora of secondary metabolites involved in defense against TG could be induced by jasmonic acid signaling pathway. However, the constitutively present of salicylic acid in SG might be a suppressor of jasmonate signaling and thus misdirect tea plants against TG. Furthermore, flavonoids and terpenoids biosynthesis pathways were highly activated in RG to constitute the chemical barrier on TG feeding behavior. In contrast, fructose and theanine, which can act as feeding stimulants were observed to highly accumulate in SG. Being present in the major hub, 39 transcription factors or protein kinases among putative candidates were identified as master regulators from protein-protein interaction network analysis. Together, the current study provides a comprehensive gene expression and metabolite profiles, which can shed new insights into the molecular mechanism of tea defense against TG. The candidate genes and specific metabolites identified in the present study can serve as a valuable resource for unraveling the possible defense mechanism of plants against various biotic stresses.

Highlights

Plants are sessile organisms and continuously challenged by a wide variety of abiotic and biotic stress factors in their natural habitat
Our results demonstrated that terpenoid synthesis, phenylpropanoid biosynthesis, JA and brassinosteroid signaling pathways were highly activated in response to tea geometrid (TG) attack
Phenylpropanoid and terpenoid biosynthesis related pathways were more highly enriched and shown a higher expression level in RG (Fig 1). We detailed investigated these pathways, and we found genes encoding phenylalanine ammonia-lyase (PAL) and leucoanthocyanidin dioxygenase (LDOX), which involved in a rate-limiting step of phenolic and anthocyanin biosynthesis, respectively, were significantly induced in RG (S5 Table)

Summary

Introduction

Plants are sessile organisms and continuously challenged by a wide variety of abiotic and biotic stress factors in their natural habitat. The partially known molecular mechanisms in response to herbivore insect attack start with the recognition of defense elicitors (e.g., fatty acidamino acid conjugates (FACs) and β-glucosidase) in insect oral secretions and signals from mechanically injured plant cells. The recognition of these elicitors or signals induces convergent intracellular signaling pathways, such as calcium ion signaling (Ca2+-dependent protein kinases, CPKs), phosphorylation cascades (mitogen-activated protein kinases, MAPKs) cascades, leucinerich repeat receptor-like kinases (LRR-RLKs), and hormonal signaling (e.g., salicylic acid (SA) and jasmonic acid (JA)) in plant cells, which result in the reprogramming of the transcriptome [1,2]. The underlying mechanisms of plant-insect interactions and the identification of new ways to improve plant resistance have been considered as an important field of research

Methods

Results

Discussion

Conclusion