Functional and genomic insights into the pathogenesis of Burkholderia species to rice

Abstract

SummaryA number of species of bacteria from the genus Burkholderia have been shown to be causal agents of diseases of rice. These diseases, caused by Burkholderia glumae, B. gladioli and B. plantarii, are becoming increasingly common across the globe. This is particularly so for B. glumae, whose ability to grow at elevated temperatures suggests that it may become a prevalent problem in an era of global warming. Despite the increasing threat to rice, relatively little is known about the virulence mechanisms employed by these pathogens. Work over the last 5 years has provided an increasing insight into these factors and their control by environmental and other cues. In addition, the determination of a number of genome sequences has allowed bioinformatic predictions of further possible mechanisms, which can now be investigated experimentally. Here, we review recent advances in the understanding of virulence of Burkholderia to rice, to include discussion of the roles of toxins, type II secreted enzymes, type III secreted effectors and motility as well as their regulation by quorum sensing, two-component systems and cyclic di-GMP signalling. Finally, we consider a number of approaches for the control of bacterial virulence through the modulation of quorum sensing and toxin degradation.

Members of the genus Burkholderia: good and bad guys

“…One intriguing case with great potential for agricultural applications is represented by Burkholderia gladioli , which is a well-known pathogen of plants (e.g. causing rice panicle blight) 60 as well as humans 61 – 63 . However, recent work has demonstrated that some B. gladioli strains live endophytically within various wild and ancient Zea plants without causing any disease symptoms 64 , 65 .…”

Saline Environments as a Source of Potential Quorum Sensing Disruptors to Control Bacterial Infections: A Review

“…Last, QSIs and mostly QQ organisms isolated from marine and saline environments could also be used in the future in agriculture since many bacterial phytopathogens that induce economic losses control their virulence or virulence associated functions through QS (Table 1) (reviews: [288,289]). This is the case for instance of Pectobacterium carotovorum [186,188,290] (review: [291]), P. atrosepticum [179,180], Erwinia amylovora [173] (review: [292]) , Burkholderia glumae (review: [293]), Ralstonia solanacearum (review: [294]), and Agrobacterium tumefaciens (review: [19]) that regulate motility, plasmid transfer, and the synthesis of macerating exoenzymes, amongst others, through such intercellular communication systems. To date, promising results have been obtained using different compounds or bacterial strains to quench QS-regulated virulence function in in vivo assays in plants, for instance, in tomato ( Solanum lycopersicum; [295,296]) or potato ( Solanum tuberosum ; [70,71,74,115,183,297]).…”

Isolation and characterization of a novel metagenomic enzyme capable of degrading bacterial phytotoxin toxoflavin

“…Toxicity of bacterial toxoflavin as a major virulence factor has been assigned to its ability to function as an active electron carrier between NADH and oxygen. The action of toxoflavin bypasses the cellular cytochrome system and causes the generation of hydrogen peroxide in the presence of oxygen and light [ 5 , 6 ]. This may also explain why toxoflavin shows antibacterial, antifungal and herbicidal activities [ 7 ].…”

“…Infection of toxoflavin-producing bacteria, particularly seed-borne B . glumae , has led to severe losses in rice crops in the world [ 6 , 8 , 9 ]. Bacterial grain rot occurring at the flowering stage of rice under high degree of temperature and moisture caused a significant loss in the rice yield up to 34%.…”