A Novel Multidomain Polyketide Synthase Is Essential for Zeamine Production and the Virulence of Dickeya zeae

Abstract

Dickeya zeae is the causal agent of the rice foot rot disease, but its mechanism of infection remains largely unknown. In this study, we identified and characterized a novel gene designated as zmsA. The gene encodes a large protein of 2,346 amino acids in length, which consists of multidomains arranged in the order of N-terminus, β-ketoacyl synthase, acyl transferase, acyl carrier protein, β-ketoacyl reductase, dehydratase. This multidomain structure and sequence alignment analysis suggest that ZmsA is a member of the polyketide synthase family. Mutation of zmsA abolished antimicrobial activity and attenuated the virulence of D. zeae. To determine the relationship between antimicrobial activity and virulence, active compounds were purified from D. zeae EC1 and were structurally characterized. This led to identification of two polyamino compounds, i.e., zeamine and zeamine II, that were phytotoxins and potent antibiotics. These results have established the essential role of ZmsA in zeamine biosynthesis and presented a new insight on the molecular mechanisms of D. zeae pathogenicity.

A Sfp-type phosphopantetheinyl transferase ZmsO is essential for zeamines production and the virulence of Dickeya zeae

“…The transposon inserted mutant EM236 was obtained following the methods described previously (Zhou et al 2011). The both flanking sequences of Tn5 were amplified and sequenced, and the ORF of zmsO was determined following the methods described previously (Cheng et al 2013;Liu and Chen 2007).…”

“…Phylogenetic analysis of Dickeya species showed that D. zeae is most distinct from other species and contains more sequevars than others (Parkinson et al 2009). This genetic diversity may explain the wide distribution of D. zeae, and the diseases caused by this bacterial pathogen have been documented in many different regions and countries around the world (SabetOur curiosity on the host range determinants and pathogenic mechanisms of D. zeae has led to identification of zeamine and zeamine II, which are structurally similar polyketide molecules with potent antimicrobial activities (Wu et al 2010;Zhou et al 2011;Liao et al 2015). In addition, zeamines are also important phythotoxins which inhibit rice seeds germination, and accelerate disease symptom development in potato and Chinese cabbages (Zhou et al 2011).…”

“…This genetic diversity may explain the wide distribution of D. zeae, and the diseases caused by this bacterial pathogen have been documented in many different regions and countries around the world (SabetOur curiosity on the host range determinants and pathogenic mechanisms of D. zeae has led to identification of zeamine and zeamine II, which are structurally similar polyketide molecules with potent antimicrobial activities (Wu et al 2010;Zhou et al 2011;Liao et al 2015). In addition, zeamines are also important phythotoxins which inhibit rice seeds germination, and accelerate disease symptom development in potato and Chinese cabbages (Zhou et al 2011). Disruption of zeamines production significantly decreases the pathogenicity of D. zeae on rice seeds, Chinese cabbage and potato (Zhou et al 2011;Cheng et al 2013).…”

“…In addition, zeamines are also important phythotoxins which inhibit rice seeds germination, and accelerate disease symptom development in potato and Chinese cabbages (Zhou et al 2011). Disruption of zeamines production significantly decreases the pathogenicity of D. zeae on rice seeds, Chinese cabbage and potato (Zhou et al 2011;Cheng et al 2013). Two genes associated with the biosynthesis of zeamines in D. zeae have been characterized recently with zmsA encoding a polyketide synthase (Zhou et al 2011), and zmsK encoding a nonribosomal peptide synthase (Cheng et al 2013).…”

“…Disruption of zeamines production significantly decreases the pathogenicity of D. zeae on rice seeds, Chinese cabbage and potato (Zhou et al 2011;Cheng et al 2013). Two genes associated with the biosynthesis of zeamines in D. zeae have been characterized recently with zmsA encoding a polyketide synthase (Zhou et al 2011), and zmsK encoding a nonribosomal peptide synthase (Cheng et al 2013). Zeamines have also been identified from Serratia plymuthica RVH1, and a gene cluster containing 18 ORFs has been designated responsible for zeamines production (Masschelein et al 2013).…”