Nano Biosensor Project2

Project_ Actin_3Stomatal Immunity: The actin cytoskeleton at the interface of host-pathogen-environment signaling.

The current favored model for the regulation of actin dynamics posits that actin filaments are constantly rearranged via polymerization, severing, and depolymerization, processes largely governed by the activity of profilin andactin depolymerizing factors (ADFs), respectively. However, the purpose(s) of this incessant re-modeling are largely unknown. Our working hypothesis is: Actin remodeling is important for mediating plant immunity against pathogens. To test this, we are using a combination of quantitative cell biology, an analysis of the convergence of hormone and immune signaling, and classical plant pathology-based approaches to define 1) How the organization of the actin cytoskeleton support the spatiotemporal dynamics of stomatal immunity, 2) How immune hormone signaling nodes linked, 3) How pathogens target cytoskeletal regulation to defeat immunity, and finally, 4) How plants sense cytoskeletal perturbation to activate immunity.


Recent studies have established that stomatal closure is an important output of innate immunity in plants. In collaboration with Dr. Sheng Yang He, we are using pathogen associated molecular patterns (PAMPs) and live bacteria, including plant pathogenic bacteria (e.g., Pseudomonas syringae pv. tomato [Pst] DC3000) to elucidate the core signaling components involved in stomatal immunity – PAMP recognition and signaling associated with stomata closure and blocking of pathogen invasion and growth. While significant knowledge gaps still remain, our data indicate that actin is linked to many events associated with the activation of stomatal immunity, including hormone signaling associated with the perception of abiotic and biotic stress. We are developing the stomatal guard cells as a paradigm for the study, and further dissection, of the molecular-genetic links between actin dynamics and the pathogen response.

Relevant publications:

Shimono, M., et al. (2016). The Pseudomonas syringae type III effector HopG1 induces actin filament remodeling in Arabidopsis in association with disease symptom development. In revision, Plant Physiol.

Li, J., Henty-Ridilla, J.L., Staiger, B.H., Day, B., and Staiger, C.J. (2015). Capping protein integrates multiple MAMP signaling pathways to modulate actin dynamics during plant innate immunity. Nature Comm.  28: 7206. doi: 10.1038/ncomms8206.

Henty-Ridilla, J.L., Li, J., Day, B., and Staiger, C.J. (2014). ADF4 regulates actin dynamics during innate immune signaling. Plant Cell. 26: 340-352

Porter, K., Shimono, M., Tian, M., and Day, B. (2012). Arabidopsis Actin-depolymerizing Factor-4 links pathogen perception, defense activation and transcription to cytoskeletal dynamics. PLoS Pathogens, 8(11): e1003006. doi:10.1371/journal.ppat.1003006

Tian, M., Chaudhry, F., Ruzicka, D.R., Meagher, R.B., Staiger, C.J., and Day, B. (2009). Arabidopsis actin depolymerizing factor AtADF4 mediates defense signal transduction triggered by the Pseudomonas syringae effector AvrPphB. Plant Physiol. 150: 815-824. 

Relevant publications:

Henty-Ridilla, J.L., Li, J., Day, B., and Staiger, C.J. (2014). ADF4 regulates actin dynamics during innate immune signaling. Plant Cell. 26: 340-352

Henty, J.L., Shimono, M., Li, J., Chang, J.H., Day, B.*, and Staiger, C.J.* (2013). The plant actin cytoskeleton is a novel component of innate immunity. PLoS Path. 9: e1003290. doi:10.1371/journal.ppat.1003290. *co-corresponding authors.

Day, B., Henty, J., Porter, K., and Staiger, C. (2011). The pathogen-actin connection: A platform for defense signaling in plants. Ann. Rev. Phytopathol. 49: 483-506.