Adi3 is a Pdk1-interacting AGC kinase that negatively regulates plant cell death.
Bacterial speck disease in tomato is caused by Pseudomonas syringae pv. tomato. Resistance to this disease is conferred by the host Pto kinase, which recognizes P. s. pv. tomato strains that express the effector AvrPto. We report here that an AvrPto-dependent Pto-interacting protein 3 (Adi3) is a member of the AGC family of protein kinases. In mammals, AGC kinases are regulated by 3-phosphoinositide-dependent protein kinase-1 (Pdk1). We characterized tomato Pdk1 and showed that Pdk1 and Pto phosphorylate Adi3. Gene silencing of Adi3 in tomato causes MAPKKKalpha-dependent formation of necrotic lesions. Use of a chemical inhibitor of Pdk1, OSU-03012, also implicates Pdk1 and Adi3 in plant cell death regulation. Adi3 thus appears to function analogously to the mammalian AGC kinase protein kinase B/Akt by negatively regulating cell death via Pdk1 phosphorylation. We speculate that the negative regulatory function of Adi3 might be subverted by interaction with Pto/AvrPto, leading to host cell death that is associated with pathogen attack.
Devarenne
Timothy P
TP
Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14853-1801, USA.
Ekengren
Sophia K
SK
Pedley
Kerry F
KF
Martin
Gregory B
GB
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D020868:Gene Silencing; D017343:Genes, Plant; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000201:enzymology; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; D010940:Plant Proteins; C081695:avrPto protein, Pseudomonas syringae; C084354:Pto protein, Lycopersicon; D064413:3-Phosphoinositide-Dependent Protein Kinases; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases