Location: Plant Gene Expression CenterTitle: Comparative genomics screen identifies microbe-associated molecular patterns form Candidatus Liberibacter sp. that elicit immune responses in plants
|CHEN, YUAN - University Of California|
|BENDIX, CLAIRE - University Of California|
Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 1/17/2020
Citation: Chen, Y., Bendix, C., Lewis, J.D. 2020. Comparative genomics screen identifies microbe-associated molecular patterns from Candidatus Liberibacter spp. that elicit immune responses in plants. Molecular Plant-Microbe Interactions. 33(3):539-552. https://doi.org/10.1094/MPMI-11-19-0309-R.
Interpretive Summary: Citrus greening or Huanglongbing (HLB) is a devastating disease that is decimating the citrus industry. No resistant varieties of citrus are available and control measures are highly limited. We carried out a big-data screen to identify potential small molecules that trigger immune responses. We demonstrated that two small molecules could trigger immune responses in many plant species including citrus. By boosting immunity in citrus, these molecules could help prevent or reduce HLB infection. This could provide another tool for growers to combat HLB and provide consumers with enhanced food security.
Technical Abstract: Citrus Huanglongbing (HLB), caused by phloem-limited Candidatus Liberibacter bacteria, is a destructive disease threatening the worldwide citrus industry. The mechanisms of pathogenesis are poorly understood and no efficient strategy is available to control HLB. Here, we used a comparative genomics screen to identify candidate microbe-associated molecular patterns (MAMPs) from Ca. Liberibacter species. We identified the core genome from multiple Ca. Liberibacter pathogens, and searched for core genes with signatures of positive selection. We hypothesized that genes encoding putative MAMPs would evolve to reduce recognition by the plant immune system, while retaining their essential functions. To efficiently screen candidate MAMP peptides, we established a high-throughput microtiter plate-based screening assay, particularly for citrus, that measured reactive oxygen species (ROS) production, which is a common immune response in plants. We found that two peptides could elicit ROS production in Arabidopsis and Nicotiana benthamiana. One of these peptides also elicited ROS production and defense gene expression in HLB-tolerant citrus genotypes, and induced MAMP-triggered immunity against the bacterial pathogen Pseudomonas syringae. Our findings identify MAMPs that boost immunity in citrus and could help prevent or reduce HLB infection.