Psyllids are major vectors of plant diseases, including Candidatus Liberibacter solanacearum (CLso), the bacterial agent associated with 'zebra chip' disease in potatoes and 'carrot yellows' disease i...

Phylogenomics of Liberibacter sheds light on new species and strain diversity, putative horizontal transmission, and nutritional functions in willow psyllid symbioses within riparian ecosystems

Unlike obligate symbionts that are permanently associated with their hosts, facultative symbionts rarely show direct nutritional contributions, especially under nutrient-limited conditions. This study...

Click on the article title to read more.

The citrus disease Huanglongbing (HLB) in Asia and the US is caused by Candidatus Liberibacter asiaticus (CLas), which is primarily transmitted by Dia…

“Candidatus Liberibacter spp.” are insect-vectored, fastidious, and vascular-limited phytopathogens. They are the presumptive causal agents of potato …

Click on the article title to read more.

Plants secrete a variety of proteases as a defense response during infection by microbial pathogens. However, the relationship between their catalytic activities and antimicrobial functions remains largely unknown. Particularly, few biologically relevant substrates of these proteases have been identified. Huanglongbing (HLB) has been a major threat to the citrus industry worldwide. The HLB-associated bacterium, "Candidatus Liberibacter asiaticus" (Las), was previously shown to deploy an inhibitor of papain-like cysteine proteases (PLCPs) to promote disease in citrus. In this study, we identified an outer membrane protein (OMP) of Las, LasOMP1, as a substrate of the citrus PLCP CsRD21a. LasOMP1 is one of the most highly expressed genes in Las. CsRD21a cleaves LasOMP1 and produces cleaved peptide products, which could be detected in vitro and in HLB-diseased citrus plants. We found that CsRD21a targets the N-terminal portion of LasOMP1, potentially at an extracellular loop region. Importantly, transgenic sweet orange overexpressing CsRD21a showed reduced Las populations and improved plant growth, highlighting that engineering this protease is a promising strategy to enhance HLB resistance in citrus. Together, our work reveals a pathogen-derived substrate of plant PLCPs and suggests bacterial OMPs may be direct targets of plant defense.

Expression of the key immune regulator NPR1 in citrus generates tolerance to HLB disease by preventing excess callose and ROS accumulation and maintaining

Citrus Huanglongbing (HLB), caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas) and considered the most destructive citrus disease worldwide, has long been regarded as a typical bacterial infection. However, recent compelling evidence shows that CLas drives HLB through chronic effector-triggered immunity, not via direct pathogenicity, thereby redefining HLB as an immune-mediated disease (Huang et al.).

Scientific Reports - Spatial chemistry of citrus reveals molecules bactericidal to Candidatus Liberibacter asiaticus