Homologous RXLR effectors from Hyaloperonospora arabidopsidis and Phytophthora sojae suppress immunity in distantly related plants.
Diverse pathogens secrete effector proteins into plant cells to manipulate host cellular processes. Oomycete pathogens contain large complements of predicted effector genes defined by an RXLR host cell entry motif. The genome of Hyaloperonospora arabidopsidis (Hpa, downy mildew of Arabidopsis) contains at least 134 candidate RXLR effector genes. Only a small subset of these genes is conserved in related oomycetes from the Phytophthora genus. Here, we describe a comparative functional characterization of the Hpa RXLR effector gene HaRxL96 and a homologous gene, PsAvh163, from the Glycine max (soybean) pathogen Phytophthora sojae. HaRxL96 and PsAvh163 are induced during the early stages of infection and carry a functional RXLR motif that is sufficient for protein uptake into plant cells. Both effectors can suppress immune responses in soybean. HaRxL96 suppresses immunity in Nicotiana benthamiana, whereas PsAvh163 induces an HR-like cell death response in Nicotiana that is dependent on RAR1 and Hsp90.1. Transgenic Arabidopsis plants expressing HaRxL96 or PsAvh163 exhibit elevated susceptibility to virulent and avirulent Hpa, as well as decreased callose deposition in response to non-pathogenic Pseudomonas syringae. Both effectors interfere with defense marker gene induction, but do not affect salicylic acid biosynthesis. Together, these experiments demonstrate that evolutionarily conserved effectors from different oomycete species can suppress immunity in plant species that are divergent from the source pathogen's host.
Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA 24061-0329, USAChemistry Research Unit, Center of Medical, Agricultural, and Veterinary Entomology, US Department of Agriculture, Agricultural Research Service, Gainesville, FL 32608, USAVirginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061-0329, USA.
Ryan G
RG
Anderson
Megan S
MS
Casady
Rachel A
RA
Fee
Martha M
MM
Vaughan
Devdutta
D
Deb
Kevin
K
Fedkenheuer
Alisa
A
Huffaker
Eric A
EA
Schmelz
Brett M
BM
Tyler
John M
JM
McDowell
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D005075:Biological Evolution; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D009868:Oomycetes / Q000502:physiology*; D010838:Phytophthora / Q000502:physiology; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000502:physiology; D016415:Sequence Alignment; D013025:Glycine max / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D014026:Nicotiana / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D019076:Transgenes
D005936:Glucans; D011506:Proteins; C048306:callose