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Title: A recombinant flagellin fragment, which includes the epitopes flg22 and flgII-28, provides a useful tool to study flagellin-triggered immunity

Author
item CIARRONI, SERENA - University Of Tuscia
item Clarke, Christopher
item LIU, HAIJIE - Virginia Tech
item LEVI, NOAM - Virginia Tech
item MAZAGLIA, ANGELO - University Of Tuscia
item BALESTRA, GIORGIO - University Of Tuscia
item VINATZER, BORIS - Virginia Tech

Submitted to: Journal of General Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2017
Publication Date: 3/23/2018
Publication URL: http://handle.nal.usda.gov/10113/5928776
Citation: Ciarroni, S., Clarke, C.R., Liu, H., Levi, N.E., Mazaglia, A., Balestra, G.M., Vinatzer, B.A. 2018. A recombinant flagellin fragment, which includes the epitopes flg22 and flgII-28, provides a useful tool to study flagellin-triggered immunity. Journal of General Plant Pathology. https://doi.org/10.1007/s10327-018-0779-2.

Interpretive Summary: Plants are able detect conserved parts of the bacterial protein known as flagellin to trigger immune responses and prevent infection. Two separate regions of flagellin are thought to independently contribute to elicitation of immunity in nightshade crops. We tested whether or not the two regions have any interactions when combined as a single fragment and used as an elicitor of plant immunity. The combined fragment was able to trigger immunity in one crop species that was blind to both of the two smaller independent regions. This result demonstrates that recognition of bacterial flagellin cannot be fully elucidated using only the two independent active elicitor regions of flagellin. These results will be used by researchers to further elucidate plant responses to pathogens and develop strategies for plants to evade infection.

Technical Abstract: Plants and animals both independently evolved the ability to recognize flagellin (also called FliC), the building block of the bacterial flagellum, as part of their innate immune response. Most plants recognize one or two short epitopes of FliC: flg22 and flgII-28. However, since most research in plants has been performed with flg22 and flgII-28 and not with the actual FliC protein, the importance of any FliC region beyond the two epitopes in plant immunity is poorly understood. Here we report cloning, over-expression, and purification of a Pseudomonas syringae FliC fragment from amino acid 1 to 143, which includes both FliC epitopes and the adjacent alpha helices. Using FliC1-143 does not reveal any additional FliC recognition capabilities in Arabidopsis thaliana beyond flg22. However, while the kiwifruit species Actinidia arguta does not recognize either flg22 or flgII-28, treatment of A. arguta leaves with FliC1-143 triggers a significant reactive oxygen response. This result suggests that in some plant species recognition of FliC requires regions of FliC beyond the two well-known epitopes and that the FliC1-143 represents a useful tool in the study of plant immunity.