Comparative transcriptome analyses revealed differential strategies of roots and leaves from methyl jasmonate treatment Baphicacanthus cusia (Nees) Bremek and differentially expressed genes involved in tryptophan biosynthesis.

Wenjin Lin,Shuju Ning,Xiaogui Gong,Qi Ye,Wei Huang,Daozhi Wei,Anil Kumar Singh

doi:10.1371/journal.pone.0212863

Wenjin Lin, Shuju Ning + Show 5 more

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https://doi.org/10.1371/journal.pone.0212863

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Abstract

Baphicacanthus cusia (Nees) Bremek (B. cusia) is an effective herb for the treatment of acute promyelocytic leukemia and psoriasis in traditional Chinese medicine. Methyl jasmonate (MeJA) is a well-known signaling phytohormone that triggers gene expression in secondary metabolism. Currently, MeJA-mediated biosynthesis of indigo and indirubin in B. cusia is not well understood. In this study, we analyzed the content of indigo and indirubin in leaf and root tissues of B. cusia with high-performance liquid chromatography and measured photosynthetic characteristics of leaves treated by MeJA using FluorCam6 Fluorometer and chlorophyll fluorescence using the portable photosynthesis system CIRAS-2. We performed de novo RNA-seq of B. cusia leaf and root transcriptional profiles to investigate differentially expressed genes (DEGs) in response to exogenous MeJA application. The amount of indigo in MeJA-treated leaves were higher than that in controled leaves (p = 0.004), and the amounts of indigo in treated roots was higher than that in controlled roots (p = 0.048); Chlorophyll fluorescence of leaves treated with MeJA were significantly decreased. Leaves treated with MeJA showed lower photosynthetic rate compared to the control in the absence of MeJA. Functional annotation of DEGs showed the DEGs related to growth and development processes were down-regulated in the treated leaves, while most of the unigenes involved in the defense response were up-regulated in treated roots. This coincided with the effects of MeJA on photosynthetic characteristics and chlorophyll fluorescence. The qRT-PCR results showed that MeJA appears to down-regulate the gene expression of tryptophan synthase β-subunits (trpA-β) in leaves but increased the gene expression of anthranilate synthase (trp 3) in roots responsible for increased indigo content. The results showed that MeJA suppressed leaf photosynthesis for B. cusia and this growth-defense trade-off may contribute to the improved adaptability of B. cusia in changing environments.

Highlights

For plants to survive in nature, they need to make choices when faced with various biotic or abiotic stresses in their surrounding environments, resulting in the production of chemical defenses [1, 2]
Comparative transcriptome analyses of B. cusia treated by Methyl jasmonate (MeJA) and differentially expressed genes (DEGs) involved in tryptophan biosynthesis
Comparative transcriptome analyses of B. cusia treated by MeJA and DEGs involved in tryptophan biosynthesis of unknown nucleotides, there were 280,702,858 high-quality reads obtained from roots and 267,021,714 from leaves

Summary

Introduction

For plants to survive in nature, they need to make choices when faced with various biotic or abiotic stresses in their surrounding environments, resulting in the production of chemical defenses [1, 2]. Jasmonates (JAs) -mediated induced resistance is an important mechanism of phytochemical defense [4, 5]. Previous genome-wide transcriptome profile analysis discovered that treating plants with JAs such as MeJA can induce extensive transcriptional alterations via the biosynthesis of terpenoids [13,14,15], phenylpropanoids [16,17,18], alkaloids [19,20,21] and volatile organic compounds [22, 23]

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