Involvement of PPS3 Phosphorylated by Elicitor-Responsive Mitogen-Activated Protein Kinases in the Regulation of Plant Cell Death

• Published in: Plant physiology (Bethesda) 2005-12, Vol.139 (4), p.1914-1926
• Main Authors: Katou, Shinpei, Yoshioka, Hirofumi, Kawakita, Kazuhito, Rowland, Owen, Jones, Jonathan D.G, Mori, Hitoshi, Doke, Noriyuki
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; Amino acids; Antibodies; apoptosis; Arabidopsis thaliana; Base Sequence; Biological and medical sciences; Cell Death; Cell physiology; Cloning, Molecular; Complementary DNA; DNA, Plant - genetics; Enzyme Activation; Fundamental and applied biological sciences. Psychology; Gels; gene expression regulation; Gene Silencing; Genes, Plant; host-pathogen relationships; MAP Kinase Signaling System; mitogen-activated protein kinases; Mitogen-Activated Protein Kinases - chemistry; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Molecular and cellular biology; Molecular Sequence Data; Molecular Weight; Nicotiana benthamiana; Nicotiana tabacum; nucleotide sequences; Phosphorylation; Plant Cells; plant proteins; Plant Proteins - metabolism; plant viruses; Plants - genetics; Plants - metabolism; Plants Interacting with Other Organisms; polyacrylamide gel electrophoresis; Potato virus X; potatoes; protein kinases; protein phosphorylation; RNA; sequence alignment; Sequence Homology, Amino Acid; Signal transduction; Solanum tuberosum; tobacco; Transcription factors; Tubers; virus-induced gene silencing
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.105.066795

Mitogen-activated protein kinase (MAPK) cascades play pivotal roles in plant innate immunity. Overexpression of StMEK1[superscript DD], a constitutively active MAPK kinase that activates salicylic acid-induced protein kinase (SIPK) and wound-induced protein kinase (WIPK), provokes hypersensitive response-like cell death in Nicotiana benthamiana. Here we purified a 51-kD MAPK, which was activated in potato (Solanum tuberosum) tubers treated with hyphal wall elicitor of a plant pathogen, and isolated the cDNA designated StMPK1. The deduced amino acid sequence of the StMPK1 showed strong similarity to stress-responsive MAPKs, such as tobacco (Nicotiana tabacum) SIPK and Arabidopsis (Arabidopsis thaliana) AtMPK6. To investigate the downstream signaling of StMPK1, we identified several proteins phosphorylated by StMPK1 (PPSs) using an in vitro expression cloning method. To dissect the biological function of PPSs in the plant defense, we employed virus-induced gene silencing (VIGS) in N. benthamiana. VIGS of NbPPS3 significantly delayed cell death induced by the transient expression of StMEK1[superscript DD] and treatment with hyphal wall elicitor. Furthermore, the mobility shift of NbPPS3 on SDS-polyacrylamide gel was induced by transient expression of StMEK1[superscript DD]. The mobility shift of NbPPS3 induced by StMEK1[superscript DD] was not compromised by VIGS of WIPK or SIPK alone, but drastically reduced by the silencing of both WIPK and SIPK. This work strongly supports the idea that PPS3 is a physiological substrate of StMPK1 and is involved in cell death activated by a MAPK cascade.