Title : A barley powdery mildew candidate effector regulates host immune responses through destabilizing HvCAT1
Abstract:
Biotrophic fungal pathogens secrete effector proteins to regulate host immunity and to establish successful colonization. Barley powdery mildew, Blumeria graminis f.sp. hordei (Bgh), is an obligate biotrophic fungus that is predicted to have more than 500 candidate secreted effector proteins (CSEPs). However, only a small number of these CSEPs have been characterized and their biochemical functions are poorly understood. Here, we describe the characterization and functions of a candidate Bgh effector. Bgh CSEP27 was identified to trigger cell-death and enhance H2O2 accumulation using Agrobacteria-mediated transient expression in N. benthamiana. A barley catalase, HvCAT1, was further identified to interact with CSEP27 in yeast, in vitro and in planta. HvCAT1 was recruited and accumulated into plant nucleus in the presence of CSEP27. Transient expression of HvCAT1 suppressed CSEP27-induced cell-death and H2O2 accumulation in N. benthamiana. Interestingly, CSEP27 could promote proteasomal degradation of HvCAT1. Silencing of HvCAT1 in barley enhances the susceptibility to Bgh, while overexpression of CSEP27 in barley increased Bgh haustorium formation in epidermal cells, indicating that HvCAT1 is essential for barley disease resistance and CSEP27 is likely a virulent factor from Bgh. Taken together, our data suggest that Bgh candidate effector CSEP27 regulates host immune responses by destabilizing a host factor, HvCAT1.
Key Words: Fungal Pathogen, Effector, Virulence, Plant Disease Resistance
