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

A 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.