The Wall-Associated Receptor-Like Kinase TaWAK7D Is Required for Defense Responses to Rhizoctonia cerealis in Wheat.

Haijun Qi,Zengyan Zhang,Liangjie Lv,Feilong Guo,Xiuliang Zhu

doi:10.3390/ijms22115629

Abstract

Sharp eyespot, caused by necrotrophic fungus Rhizoctonia cerealis, is a serious fungal disease in wheat (Triticum aestivum). Certain wall-associated receptor kinases (WAK) mediate resistance to diseases caused by biotrophic/hemibiotrophic pathogens in several plant species. Yet, none of wheat WAK genes with positive effect on the innate immune responses to R. cerealis has been reported. In this study, we identified a WAK gene TaWAK7D, located on chromosome 7D, and showed its positive regulatory role in the defense response to R. cerealis infection in wheat. RNA-seq and qRT-PCR analyses showed that TaWAK7D transcript abundance was elevated in wheat after R. cerealis inoculation and the induction in the stem was the highest among the tested organs. Additionally, TaWAK7D transcript levels were significantly elevated by pectin and chitin treatments. The knock-down of TaWAK7D transcript impaired resistance to R. cerealis and repressed the expression of five pathogenesis-related genes in wheat. The green fluorescent protein signal distribution assays indicated that TaWAK7D localized on the plasma membrane in wheat protoplasts. Thus, TaWAK7D, which is induced by R. cerealis, pectin and chitin stimuli, positively participates in defense responses to R. cerealis through modulating the expression of several pathogenesis-related genes in wheat.

Highlights

7D, designed as TaWAK7D, and investigated its defense role in wheat defense response to R. cerealis, as well as analyzed the protein subcellular localization. These results suggested that TaWAK7D positively participated in the defense against R. cerealis infection through activating the expression of several pathogenesis-related (PR) genes, including β-1,3-Glucanase, Chitinase3, Chitinase4, PR1 and PR17
QRT-PCR analysis showed that as shown in Figure 1B, after inoculation with R. cerealis, TaWAK7D transcript in R. cerealis-resistant wheat cultivar CI12633 was significantly increased at 2 dpi and reached a peak at 4 dpi (~4.93-fold) compared with the untreated one, and decreased to 0.83 fold at 10 dpi, implying that the gene may be involved in the early defense response to the fungal infection
The analyses showed that the transcript levels of β-1, 3-Glucanase, Chitinase3, Chitinase4, PR1 and PR17 significantly decreased in TaWAK7D-silenced CI12633 plants relative to the barley stripe mosaic virus (BSMV):GFP-infected CI12633 plants

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Wheat (Triticum aestivum) is one of the most important staple crops [1]. The wheat sharp eyespot disease, primarily caused by the necrotrophic fungus Rhizoctonia cerealis, is one destructive disease for wheat in many regions of the world [2,3]. In China, sharp eyespot disease has become an economically important wheat disease in the past two decades; 6.67–9.33 million hectares of wheat fields are affected by this disease per year [4,5]

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Results

Conclusion