Bacterial panicle blight of rice (BPBR), also known as bacterial grain rot of rice, is a serious seed
borne disease of rice caused by
Burkholderia glumae. Because the optimal temperature range for
the growth of
B. glumae is relatively high (30–35°C), it is considered that this disease may occur
more frequently with current global climate change. Horizontal gene transfer (HGT), also known as
lateral gene, has been proved a major driving force in prokaryotic evolution. However, the molecular
functions of these transferred genes in pathogenic bacteria especially plant pathogenic bacteria
are still not fully investigated. In this study, the whole-genome in silico analysis was performed
and found a syringopeptin synthetase (
syp) homolog in
B. glumae, which can cause bacterial
panicle blight in rice, was predicted to be horizontally transferred from
Pseudomonas ancestor
with solid confidence by phylogenetic analysis. Inoculation of rice panicles with the syp mutant
resulted in 60% lower disease index compared with the wild type (WT) parent strain, suggesting
the requirement of
syp for the full virulence of
B. glumae. Chromatography analysis of exudates
from
B. glumae showed suppression of synthesis of metabolites analogous to syringopeptin in
the mutants. All these data raise the possibility of HGT phenomenon in shaping the virulence and
adaptation of
B. glumae over evolutionary time. The photos are provided by the research team of
Prof. Zhu Bo from Shanghai Jiao Tong University, China. See pages 3222–3229 for details.
