Wheat root transcriptional responses against Gaeumannomyces graminis var. tritici

Jie Zhang,Paul H Goodwin,Haixia Yan,Runhong Sun,Xin Quan,Lihua Xie,Chao Wu,Lirong Yang,Mingcong Xia,Xiaoyun Han

doi:10.1186/s42483-020-00066-7

Abstract

Wheat root rot caused by Gaeumannomyces graminis var. tritici (Ggt) results in severe yield losses in wheat production worldwide. However, little is known about the molecular mechanism that regulates systemic symptom development in infected wheat. Fluorescent microscopy observation of the stained wheat roots infected by Ggt showed that lesions were visible when the fungus could be detected in the endodermis, pericycle and phloem at 5 days post inoculation (dpi), and rust symptoms were visible when there was extensive fungal colonization in the root cortex at 6 dpi. Transcriptome sequencing of Ggt-inoculated wheat roots and healthy control root samples was performed at 5 dpi to identify Ggt-induced gene expression changes in wheat roots at the time of lesion formation. A total of 3973 differentially expressed genes (DEGs) were identified, of which 1004 (25.27%) were up-regulated and 2969 (74.73%) were down-regulated in Ggt-inoculated wheat roots compared with those in control roots. GO annotation and KEGG pathway analysis of these DEGs revealed that many of them were associated with pathogen resistance, such as those involved in oxidation-reduction process, tryptophan biosynthesis process, and phenylpropanoid biosynthesis process. Analysis of DEGs revealed that 15 DEGs were involved in cellular regulation, 57 DEGs in signal transduction pathways, and 75 DEGs in cell wall reorganization, and 23 DEGs are pathogenesis-related proteins. Reverse transcription quantitative PCR (RT-qPCR) of 13 of those DEGs showed that these genes may play roles in wheat resistance against Ggt. Overall, this study represents the first transcriptional profiling of wheat roots in response to Ggt infection and further characterization of DEGs identified in this study may lead to better understanding of resistance against take-all in wheat.

Highlights

Wheat (Triticum aestivum L.) is the most extensively grown cereal crop and one of the four major food crops in the world (McMillan et al 2014)
In the absence of effector recognition by resistance genes, the attacking fungus would be recognized by host plant through its microbe-associated molecular patterns (MAMPs) or damage associated molecular patterns (DAMPs) that result in induction of plant defenses (De Coninck et al 2015)
Impact of Gaeumannomyces graminis var. tritici inoculation on wheat plants The leaf length of wheat seedlings infected by Ggt was significantly shorter than that of the control starting at 6 dpi (Fig. 1a)

Summary

Introduction

Wheat (Triticum aestivum L.) is the most extensively grown cereal crop and one of the four major food crops in the world (McMillan et al 2014). There are significant differences between plant resistance to root pathogens and to foliar pathogens (Mooney et al 2006; Sang et al 2010; De Coninck et al 2015). In the absence of effector recognition by resistance genes, the attacking fungus would be recognized by host plant through its microbe-associated molecular patterns (MAMPs) or damage associated molecular patterns (DAMPs) that result in induction of plant defenses (De Coninck et al 2015). Several root pathogens are known to evade or suppress this recognition through effectortriggered susceptibility, but effectors of root pathogens can be recognized, resulting in a type of resistance without activation of the programmed cell death that has been observed in foliar pathogens (De Coninck et al 2015). It is necessary to investigate the responses of plant roots to root pathogens and the corresponding defense mechanisms rather than just rely on results of plant leaves to foliar pathogens

Methods

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Discussion

Conclusion