Coexpression network analysis of the genes regulated by two types of resistance responses to powdery mildew in wheat.

Juncheng Zhang,Hongyuan Zheng,Huanju Qin,Xin Liu,Daowen Wang,Yiwen Li,Hongjie Li,Lingli Dong

doi:10.1038/srep23805

Abstract

Powdery mildew disease caused by Blumeria graminis f. sp. tritici (Bgt) inflicts severe economic losses in wheat crops. A systematic understanding of the molecular mechanisms involved in wheat resistance to Bgt is essential for effectively controlling the disease. Here, using the diploid wheat Triticum urartu as a host, the genes regulated by immune (IM) and hypersensitive reaction (HR) resistance responses to Bgt were investigated through transcriptome sequencing. Four gene coexpression networks (GCNs) were developed using transcriptomic data generated for 20 T. urartu accessions showing IM, HR or susceptible responses. The powdery mildew resistance regulated (PMRR) genes whose expression was significantly correlated with Bgt resistance were identified, and they tended to be hubs and enriched in six major modules. A wide occurrence of negative regulation of PMRR genes was observed. Three new candidate immune receptor genes (TRIUR3_13045, TRIUR3_01037 and TRIUR3_06195) positively associated with Bgt resistance were discovered. Finally, the involvement of TRIUR3_01037 in Bgt resistance was tentatively verified through cosegregation analysis in a F2 population and functional expression assay in Bgt susceptible leaf cells. This research provides insights into the global network properties of PMRR genes. Potential molecular differences between IM and HR resistance responses to Bgt are discussed.

Highlights

Because of its well characterized genome and the availability of abundant functional genomic resources, the model plant Arabidopsis thaliana has been frequently used for studying the molecular mechanisms of plant resistance to fungal pathogens including the powdery mildews Golovinomyces cichoracearum, G. orontii and Erysiphe cruciferarum[12]
gene coexpression network (GCN) analysis was conducted in order to reveal the genes and major modules involved in the two types of wheat resistance responses (IM and Hypersensitive reaction (HR)) to powdery mildew
The use of transcriptomic data from multiple T. urartu accessions showing IM, HR or susceptible phenotypes permitted the construction of robust GCNs, facilitated the identification of powdery mildew resistance regulated (PMRR) and hub-PMRR gene sets and the major modules that were correlated with Blumeria graminis f. sp. tritici (Bgt) resistance

Summary

Introduction

Because of its well characterized genome and the availability of abundant functional genomic resources, the model plant Arabidopsis thaliana has been frequently used for studying the molecular mechanisms of plant resistance to fungal pathogens including the powdery mildews Golovinomyces cichoracearum, G. orontii and Erysiphe cruciferarum[12]. Through the studies on Arabidopsis and similar investigations in other plant species, e.g., rice (Oryza sativa), tomato (Solanum lycopersicum) and barley (Hordeum vulgare), it is clear that plants generally employ a complex, two-tiered immune system to defend against pathogen attacks, namely microbe-associated molecular pattern (MAMP)-triggered immunity (MTI) and effector-triggered immunity (ETI)[13,14,15,16,17,18,19] The former is a basal immune response initiated after sensing MAMPs by plant cell surface located pattern-recognition receptors (PRRs)[13,14,15,16]. A large number of host genes take part in resistance signaling and defense processes, and they may interact in a complex manner Because of this situation, network analysis has emerged as a valuable approach for systematically uncovering and understanding the molecular complexities of plant immunity[31].

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