Research Introduction

Research in the Staskawicz laboratory is focused on elucidating the molecular basis of plant innate immunity from the perspective of both the pathogen and the host. We have emphasized the identification and characterization of bacterial effector proteins from both Pseudomonas syringae and Xanthomonas spp. with respect to the molecular events that control delivery of effector proteins to host and their sites of action within the plant host. We have studied the dual phenotype of bacterial effectors with regards to both virulence and their ability to trigger effector-mediated immunity when they are recognized by their cognate NB-LRR plant innate immune receptors. Our laboratory studies many aspects of plant innate immunity and employs cutting edge methods to answer many of the pressing questions in the field that pertain to effector recognition and NB-LRR immune receptor activation. Furthermore, we have now set out to apply basic discoveries in the field of molecular plant pathology to engineer durable resistance in agronomic crop species. 

Bacterial Spot of Tomatoes

Pepper plants (Capsicum annuum) containing the Bs2 resistance gene are resistant to strains of Xanthomonas campestris pv vesicatoria (Xcv) expressing the bacterial effector protein AvrBs2. AvrBs2 is delivered directly to the plant cell via the type III protein secretion system (TTSS) of Xcv. Upon recognition of AvrBs2 by plants expressing the Bs2 gene; a signal transduction cascade is activated leading to a bacterial disease resistance response. We have developed a novel pathosystem that consists of epitope-tagged Bs2-expressing transgenic Nicotiana benthamiana plants and engineered strains of Pseudomonas syringae pv tabaci that deliver the effector domain of the Xcv AvrBs2 protein via the TTSS of P. syringae.

Hyaloperonosprora arabidopsidis/Arabidopsis Interactions

Hyaloperonospora arabidopsidis on Arabidopsis thaliana
We have been awarded a National Science Foundation Arabidopsis 2010 grant to study effector proteins from the oomycete pathogen,Hyaloperonosprora arabidopsidis. Our understanding of the molecular basis of plant disease resistance has greatly benefited from studies that have featured different classes of pathogens interacting with Arabidopsis thaliana. In fact, current theories about plant innate immunity have heavily relied on knowledge generated from these studies. It has been hypothesized that early land plants originally contained basal immune receptors that were capable of recognizing pathogen associated molecular patterns (PAMPs) leading to the activation of basal host defense responses (8).

RPS2 Innate Immunity

Peudomonas syringae
During the last fifteen years my laboratory has been developing the Arabidopsis/Pseudomomas host-pathogen interaction system to elucidate the molecular basis of pathogen recognition and the subsequent defense signaling pathways specifying plant innate immunity. Our research has mainly concentrated on the RPS2 disease resistance-signaling pathway. The RPS2 disease resistance protein is the prototypic member of the CC/NB/LRR subclass of the NB/LRR “superfamily” of plant immune receptors.

NSF Bread Cassava Bacterial Blight

Cassava Field
Cassava bacterial blight, incited by Xanthomonas axonopodis pv. manihotis (Xam)is a serious threat to cassava plants in several developing countries in both Africa and South America. This project will first focus on the genome characterization of Xam to sequence, annotate, and characterize the constellation of bacterial effector (virulence) proteins that are present in naturally occurring field isolates of this important bacterial pathogen. The ability to rapidly and inexpensively determine the genome sequence of natural field isolates of Xam will provide novel insights into the evolution of pathogen virulence and the allelic diversity of effector genes that occur in natural populations.