Lsp family proteins regulate antibiotic biosynthesis in Lysobacter enzymogenes OH11

Ruping Wang,Fengquan Liu,Huiyong Xu,Guoliang Qian,Yangyang Zhao,Juan Zhang,Gary Y Yuen

doi:10.1186/s13568-017-0421-2

Abstract

Ax21 family proteins have been shown to play regulatory roles in plant- and animal-pathogenic species in the bacterial family Xanthomonadaceae, but the protein have not been investigated previously in the non-pathogenic members of this bacterial family. Lysobacter enzymogenes, is a non-pathogenic species known for its capacity as a biocontrol agent of plant pathogens. It is also noted for the production of antimicrobial secondary metabolites, heat stable antifungal factor (HSAF) and WAP-8294A2, that have potential for agricultural and pharmaceutical applications. The species also displays type IV pili-dependent twitching motility and the production of multiple extracellular lytic enzymes as additional biocontrol-related traits. Here, we show that L. enzymogenes strain OH11 possesses three genes widely separated in the OH11 genome that code for unique Ax21-like proteins (Lsp). By comparing the wildtype OH11 with mutant strains having a single lsp gene or a combination of lsp genes deleted, we found that each Lsp protein individually is involved in positive regulation of HSAF and WAP-8294A2 biosynthesis, but the proteins collectively do not exert additive effects in this regulation. None of the Lsp proteins were found to influence twitching motility or the production of three extracellular lytic enzymes. This study is the first to provide evidence linking Ax21-family proteins to antibiotic biosynthesis and, hence, adds new insights into the diversity of regulatory functions of Ax21 family proteins in bacteria.

Highlights

The Ax21 protein family consists of proteins related to Ax21, which was originally identified in the rice-pathogenic bacterium, Xanthomonas oryzae pv. oryzae (Xoo) and thought to activate XA21-mediated immunity in rice (Lee et al 2009)
L. enzymogenes produces three A x21Xoo‐like proteins To determine whether L. enzymogenes produces Ax21family proteins, we searched the genome of L. enzymogenes strain OH11 for genes coding for proteins homologous to Ax21Xoo
Due to they being small molecule weight proteins in L. enzymogenes, they were designated as Lsp1 (216 aa), Lsp2 (217 aa) and Lsp3 (216 aa), and they shared 41% (E value 3e−038), 28% (E value 2e−013) and 23% (E value 3e−006) identity, respectively, to Ax21Xoo (194 aa) at the amino-acid level

Summary

Introduction

The Ax21 protein family consists of proteins related to Ax21, which was originally identified in the rice-pathogenic bacterium, Xanthomonas oryzae pv. oryzae (Xoo) and thought to activate XA21-mediated immunity in rice (Lee et al 2009). Oryzae (Xoo) and thought to activate XA21-mediated immunity in rice (Lee et al 2009) This protein (referred to as Ax21Xoo in the present study), was recently shown not to be involved in triggering an immune response in rice carrying the XA21 pattern recognition receptor (Bahar et al 2014). One antibiotic of particular note is heat stable antifungal factor (HSAF), which is a tetramate-containing macrocyclic lactam with broad-spectrum antifungal activity produced by L. enzymogenes (Yu et al 2007; Li et al 2008) This antibiotic is unique in its mode of action, disrupting the biosynthesis of membrane sphingolipids, and it has a distinctive biosynthetic mechanism (Li et al 2006, 2014; Lou et al 2011). L. enzymogenes produces type IV pili (T4P), which are critical to twitching motility (movement on solid surfaces) and attachment to substrates such as fungal hyphae (Kobayashi et al 2005; Patel et al 2011, 2013)

Methods

Results

Conclusion