TY  - JOUR
A1  - Uestuen, Suayib
A1  - Börnke, Frederik
T1  - Interactions of Xanthomonas type-III effector proteins with the plant ubiquitin and ubiquitin-like pathways
JF  - Frontiers in plant science
N2  - In eukaryotes, regulated protein turnover is required during many cellular processes, including defense against pathogens. Ubiquitination and degradation of ubiquitinated proteins via the ubiquitin proteasome system (UPS) is the main pathway for the turnover of intracellular proteins in eukaryotes. The extensive utilization of the UPS in host cells makes it an ideal pivot for the manipulation of cellular processes by pathogens. Like many other Gram-negative bacteria, Xanthomonas species secrete a suite of type-III effector proteins (T3Es) into their host cells to promote virulence. Some of these T3Es exploit the plant UPS to interfere with immunity. This review summarizes T3E examples from the genus Xanthomonas with a proven or suggested interaction with the host UPS or UPS-like systems and also discusses the apparent paradox that arises from the presence of T3Es that inhibit the UPS in general while others rely on its activity for their function.
KW  - Xanthomonas
KW  - type-III effector
KW  - ubiquitin
KW  - proteasome
KW  - plant defense
Y1  - 2014
U6  - https://doi.org/10.3389/fpls.2014.00736
SN  - 1664-462X
VL  - 5
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Üstün, Suayib
A1  - Bartetzko, Verena
A1  - Börnke, Frederik
T1  - The Xanthomonas effector XopJ triggers a conditional hypersensitive response upon treatment of N. benthamiana leaves with salicylic acid
JF  - Frontiers in plant science
N2  - XopJ is a Xanthomonas type III effector protein that promotes bacterial virulence on susceptible pepper plants through the inhibition of the host cell proteasome and a resultant suppression of salicylic acid (SA) - dependent defense responses. We show here that Nicotiana benthamiana leaves transiently expressing XopJ display hypersensitive response (HR) -like symptoms when exogenously treated with SA. This apparent avirulence function of XopJ was further dependent on effector myristoylation as well as on an intact catalytic triad, suggesting a requirement of its enzymatic activity for HR-like symptom elicitation. The ability of XopJ to cause a HR-like symptom development upon SA treatment was lost upon silencing of SGT1 and NDR1, respectively, but was independent of EDS1 silencing, suggesting that XopJ is recognized by an R protein of the CC-NBS-LRR class. Furthermore, silencing of NPR1 abolished the elicitation of HR-like symptoms in XopJ expressing leaves after SA application. Measurement of the proteasome activity indicated that proteasome inhibition by XopJ was alleviated in the presence of SA, an effect that was not observed in NPR1 silenced plants. Our results suggest that XopJ - triggered HR-like symptoms are closely related to the virulence function of the effector and that XopJ follows a two-signal model in order to elicit a response in the non-host plant N. benthamiana.
KW  - Xanthomonas
KW  - type-III effector
KW  - XopJ
KW  - avirulence
KW  - salicylic acid
Y1  - 2015
U6  - https://doi.org/10.3389/fpls.2015.00599
SN  - 1664-462X
VL  - 6
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  -