Molecular characterization of HEXOKINASE1 in plant innate immunity

Abstract

Hexokinase1 (HXK1) is an Arabidopsis glucose sensor that has a variety of roles during plant growth and devlopment, including during germination, flowering, and senescence. HXK1 also acts as a positive regulator of plant immune responses. Previous research suggested that HXK1 might influence plant immune responses via responses to glucose. Plant immune responses are governed by two main pathways: PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI involves the recognition of Pathogen-Associated Molecular Patterns (PAMPs) and leads to increased callose formation and accumulation of pathogenesis response (PR) proteins. ETI acts in response to effectors secreted by Gram-negative bacteria. During ETI, the membrane-localized protein RPM1-interacting protein 4 (RIN4) becomes phosphorylated in reponse to interactions with effectors and mediates the downstream response. In this study, the effects of glucose on plant immune responses against infection with Pseudomonas syringae pv. tomato DC3000 and other P. syringae strains were investigated in the presence and absence of HXK1. Infiltration of leaves with glucose prior to infection led to decreases in bacterial populations and reductions in disease symptoms in wild-type Arabidopsis plants, indicating that glucose plays a role in plant immunity. Both PTI and ETI responses were affected. However, these effects were not observed in a hxk1 mutant, indicating that the effects of glucose on plant immune responses were mediated by HXK1-related pathways.

Genome-Wide Survey and Expression Analyses of Hexokinase Family in Poplar (Populus trichocarpa)

“…In transgenic tobacco, overexpressing invertase led to sugar accumulation, and the induction of PR-1 and PR-5 by glucose in correlation with AtHXK1 mediated the signaling and catalytic activities, suggesting the positive regulation of defense-related genes through carbohydrate metabolism [ 24 ]. Constant induction of AtHXK1 and 2 transcripts in Arabidopsis resulted in elevated resistance to the infections of necrotrophic fungi ( Alternaria brassicicola ) and bacterial P. syringae , indicating the defense and immunity roles of HXK against various pathogens [ 40 , 46 ]. The underlying mechanisms of HXK involved in regulating immunity and defense appeared to be related to altered ROS accumulation, further supported by several recent works performed on rice and apples [ 47 , 48 ].…”

“…It was shown that AtHXK1 acts as a positive regulator of plant immunity in leaves challenged by Pseudomonas syringae pv. tomato DC3000 through the glucose effect mediated by AtHXK1-related pathways [ 46 ]. Overexpression of native OsHXK1 in rice led to improved ROS accumulation and leaf resistance to virus infection [ 47 ].…”

The barley HvSTP13GR mutant triggers resistance against biotrophic fungi

“…This shift might be sensed by the intracellular hexokinase 1 or the extracellular G‐protein‐coupled receptor RGS1 (regulator of G‐protein signalling protein 1). Both proteins are reported to be involved in the activation of defence pathways, including signal transduction, gene expression, stomatal closure, cell wall restructuring, or reactive oxygen species (ROS) production (Grigston et al, 2008 ; Jing et al, 2020 ; Morkunas & Ratajczak, 2014 ; Xiao et al, 2000 ; Zhong et al, 2019 ). Here, the inactive STP13GR mutant might result in the activation of those sugar signalling pathways and promote the plant stress response.…”

The Barley HvSTP13GR mutant triggers resistance against biotrophic fungi

“…This shift might be sensed by the intracellular Hexokinase 1 or the extracellular G-protein-coupled receptor RGS1 (regulator of G-protein signaling protein 1). Both proteins are reported to be involved in the activation of defense pathways -including signal transduction, gene expression, stomatal closure, cell wall restructuring or ROS production (Grigston et al, 2008;Jing et al, 2020;Morkunas and Ratajczak, 2014;Xiao et al, 2000;Zhong et al, 2019). Here, the inactive STP13GR mutant might result in the activation of those sugar signaling pathways and promote the plants stress response.…”