Transcriptome analysis reveals key roles of AtLBR-2 in LPS-induced defense responses in plants

Sayaka Iizasa,Keiichi Watanabe,Ei’Ichi Iizasa,Yukio Nagano

doi:10.1186/s12864-017-4372-4

Sayaka Iizasa, Keiichi Watanabe + Show 2 more

Open Access

https://doi.org/10.1186/s12864-017-4372-4

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Journal: BMC Genomics	Publication Date: Dec 1, 2017
Citations: 16	License type: open-access

Affiliation: Kagoshima University, Saga University

Abstract

BackgroundLipopolysaccharide (LPS) from Gram-negative bacteria cause innate immune responses in animals and plants. The molecules involved in LPS signaling in animals are well studied, whereas those in plants are not yet as well documented. Recently, we identified Arabidopsis AtLBR-2, which binds to LPS from Pseudomonas aeruginosa (pLPS) directly and regulates pLPS-induced defense responses, such as pathogenesis-related 1 (PR1) expression and reactive oxygen species (ROS) production. In this study, we investigated the pLPS-induced transcriptomic changes in wild-type (WT) and the atlbr-2 mutant Arabidopsis plants using RNA-Seq technology.ResultsRNA-Seq data analysis revealed that pLPS treatment significantly altered the expression of 2139 genes, with 605 up-regulated and 1534 down-regulated genes in WT. Gene ontology (GO) analysis on these genes showed that GO terms, “response to bacterium”, “response to salicylic acid (SA) stimulus”, and “response to abscisic acid (ABA) stimulus” were enriched amongst only in up-regulated genes, as compared to the genes that were down-regulated. Comparative analysis of differentially expressed genes between WT and the atlbr-2 mutant revealed that 65 genes were up-regulated in WT but not in the atlbr-2 after pLPS treatment. Furthermore, GO analysis on these 65 genes demonstrated their importance for the enrichment of several defense-related GO terms, including “response to bacterium”, “response to SA stimulus”, and “response to ABA stimulus”. We also found reduced levels of pLPS-induced conjugated SA glucoside (SAG) accumulation in atlbr-2 mutants, and no differences were observed in the gene expression levels in SA-treated WT and the atlbr-2 mutants.ConclusionThese 65 AtLBR-2-dependent up-regulated genes appear to be important for the enrichment of some defense-related GO terms. Moreover, AtLBR-2 might be a key molecule that is indispensable for the up-regulation of defense-related genes and for SA signaling pathway, which is involved in defense against pathogens containing LPS.

Highlights

Lipopolysaccharide (LPS) from Gram-negative bacteria cause innate immune responses in animals and plants
Transcriptomic analysis of P. aeruginosa LPS-responsive genes in WT Arabidopsis To examine and compare the LPS-induced transcriptional changes between wild-type (WT) and the atlbr-21, we treated them with LPS from P. aeruginosa; total RNA was extracted and mRNA sequencing (RNA-Seq) analysis was performed
The RNA-Seq data obtained from untreated WT were compared with that of Pseudomonas aeruginosa LPS (pLPS)-treated WT

Summary

Introduction

Lipopolysaccharide (LPS) from Gram-negative bacteria cause innate immune responses in animals and plants. We identified Arabidopsis AtLBR-2, which binds to LPS from Pseudomonas aeruginosa (pLPS) directly and regulates pLPS-induced defense responses, such as pathogenesis-related 1 (PR1) expression and reactive oxygen species (ROS) production. The perception of LPS triggers various defense responses in plants and animals [1]. LPS-binding protein (LBP) and bactericidal/permeability-increasing protein (BPI) play important roles in the regulation of immune responses against LPS [7]. Both the proteins directly bind to LPS, BPI inhibits whereas LBP enhances the binding of LPS to Toll-like receptor 4, a mammalian LPS receptor.

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