Phosphoglycerate Kinase Is Involved in Carbohydrate Utilization, Extracellular Polysaccharide Biosynthesis, and Cell Motility of Xanthomonas axonopodis pv. glycines Independent of Clp.

Wei Guo,Hong-Jie Wang,Jian-Zhong Liu,Chu-Yun Sun,Jie Gao,Ru-Yi Su,Si-Han Gao,Gong-You Chen

doi:10.3389/fmicb.2020.00091

Abstract

Phosphoglycerate kinase (Pgk), catalyzing the reversible conversions between glycerate-1.3-2P and glycerate-3P, plays an important role in carbohydrate metabolism. Here, we show that a Pgk-deficient mutant (NΔpgk) of Xanthomonas axonopodis pv. glycines (Xag) could grow in medium with glucose, galactose, fructose, mannose, or sucrose, as the sole carbon source, suggesting that Xag may employ Entner-Doudoroff (ED) and pentose phosphate pathway (PPP), but not glycolysis, to catabolize glucose. NΔpgk could not utilize pyruvate, suggesting that Pgk might be essential for gluconeogenesis. Mutation in pgk led to a reduction of extracellular polysaccharide (EPS) biosynthesis, cell motility, and intracellular ATP. As a result, the virulence of NΔpgk was significantly compromised in soybean. NΔpgk could be fully complemented by the wild-type pgk, but not by clp (encoding Crp-like protein). qRT-PCR analyses demonstrated that pgk is regulated by the HrpG/HrpX cascade, but not by Clp. These results suggest that Pgk is involved in carbohydrate utilization, EPS biosynthesis, and cell motility of Xag independent of Clp.

Highlights

Xanthomonas axonopodis pv. glycines (Xag) is widely distributed in soybean-producing areas throughout the world (Chatnaparat et al, 2012)
We found that Phosphoglycerate kinase (Pgk) plays an important role in the catabolism of glucose and other simple sugars in Xag
N pgk still showed certain level of growth in medium with these individual sugars as the sole carbon source, suggesting that Xag may employ ED and phosphate pathway (PPP), but not glycolysis, to utilize these sugars. This is consistent with the findings from previous studies conducted in the parenchyma pathogen X. oryzae pv. oryzicola (Xoc) (Guo et al, 2015), as well as the vascular pathogens X. campestris pv. campestris (Xcc) (Lu et al, 2009) and X. oryzae pv. oryzae (Xoo) (Kim et al, 2010), which lack phosphofructokinase activity required for glycolysis

Summary

Introduction

Xanthomonas axonopodis pv. glycines (Xag) is widely distributed in soybean-producing areas throughout the world (Chatnaparat et al, 2012). Association Between Pgk and Clp. Over the past two decades, significant progress has been made on elucidating the association of carbon metabolism to virulence and quorum sensing (QS) in Xanthomonas spp., such as in X. oryzae pv. Over the past two decades, significant progress has been made on elucidating the association of carbon metabolism to virulence and quorum sensing (QS) in Xanthomonas spp., such as in X. oryzae pv. Oryzicola (Xoc), which infects rice (Guo et al, 2017) Results of these studies have shown that carbohydrate acquisition is essential for the pathogen to grow and establish a successful infection within the hosts (Tang et al, 2005; Mellgren et al, 2009). The pathogen overcomes host defenses, adapts to the hostile environment, and degrades the plant parenchyma cells to gain access to its nutritional reservoirs (Tamir-Ariel et al, 2007; Zhou et al, 2013)

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