Antagonistic control of powdery mildew host cell entry by barley calcium-dependent protein kinases (CDPKs).
Calcium-dependent protein kinases (CDPKs) are known to play pivotal roles in intracellular signaling during abiotic and biotic stress responses. To unravel potential functions of CDPKs in the course of barley (Hordeum vulgare)-powdery mildew (Blumeria graminis) interactions, we systematically analyzed the HvCDPK gene family. We found that, according to the existence of respective expressed sequence tags, at least nine paralogs are expressed in the barley leaf epidermis, the sole target tissue of powdery mildew fungi. We exemplarily selected two HvCDPKs with known full-length coding sequence for functional analysis. Transient expression of a putative constitutive active variant of one of these (HvCDPK4) in Nicotiana benthamiana triggered kinase-dependent mesophyll cell death in tobacco leaves. In a barley mlo mutant genotype, a constitutive active variant of the second paralog, HvCDPK3, partially compromised the highly effective resistance to B. graminis f. sp. hordei. A similar break of mlo resistance was seen upon expression of the junction domain of HvCDPK4, supposed to act as a dominant inhibitor of CDPK activity. Expression of a constitutive active HvCDPK3 or HvCDPK4 form also compromised penetration resistance to the inappropriate wheat powdery mildew fungus. Collectively, our data provide evidence for antagonistic roles of individual CDPK paralogs in the control of host cell entry during the early phase of powdery mildew pathogenesis.
Freymark
Gerald
G
Max-Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, D-50829 Köln, Germany.
Diehl
Tobias
T
Miklis
Marco
M
Romeis
Tina
T
Panstruga
Ralph
R
D001203:Ascomycota / Q000502:physiology*; D016923:Cell Death; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D019441:Plant Epidermis / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014026:Nicotiana / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases
D010940:Plant Proteins; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases