Involvement of CsWRKY70 in salicylic acid-induced citrus fruit resistance against Penicillium digitatum

Bing Deng,Wenjun Wang,Changqing Ruan,Shixiang Yao,Lili Deng,Kaifang Zeng

doi:10.1038/s41438-020-00377-y

Abstract

Penicillium digitatum causes serious losses in postharvest citrus fruit. Exogenous salicylic acid (SA) can induce fruit resistance against various pathogens, but the mechanism remains unclear. Herein, a transcriptome-based approach was used to investigate the underlying mechanism of SA-induced citrus fruit resistance against P. digitatum. We found that CsWRKY70 and genes related to methyl salicylate (MeSA) biosynthesis (salicylate carboxymethyltransferase, SAMT) were induced by exogenous SA. Moreover, significant MeSA accumulation was detected in the SA-treated citrus fruit. The potential involvement of CsWRKY70 in regulating CsSAMT expression in citrus fruit was studied. Subcellular localization, dual luciferase, and electrophoretic mobility shift assays and an analysis of transient expression in fruit peel revealed that the nucleus‐localized transcriptional activator CsWRKY70 can activate the CsSAMT promoter by recognizing the W-box element. Taken together, the findings from this study offer new insights into the transcriptional regulatory mechanism of exogenous SA-induced disease resistance in Citrus sinensis fruit.

Highlights

Citrus fruit is threatened by a variety of pathogens, and the decay caused by Penicillium digitatum infections accounts for most of the economic losses during postharvest storage[1,2]
We investigated the effect of different concentrations of Salicylic acid (SA) on the disease incidence and lesion size of citrus fruit
The application of 2 mM SA obviously inhibited the development of green mold, which is consistent with our study[6]

Summary

Introduction

Citrus fruit is threatened by a variety of pathogens, and the decay caused by Penicillium digitatum infections accounts for most of the economic losses during postharvest storage[1,2]. The extensive use of artificial fungicides, including thiabendazole, sodium o-phenyl phenate, and imazalil, has effectively inhibited the spread of citrus postharvest disease[3,4,5]. The emergence of resistant strains of pathogens and undesirable influences on the environment and human health caused by the wide use of these chemical fungicides have led to an increasing and urgent need for efficient and healthy alternatives to fungicide usage[6]. Salicylic acid (SA) is one of the most important hormones in plants. SA is synthesized in either the cinnamic

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Conclusion