A mitogen-activated protein kinase signals to programmed cell death induced by self-incompatibility in Papaver pollen.
Self-incompatibility (SI) in higher plants is an important mechanism to prevent inbreeding and involves specific rejection of incompatible ("self") pollen. In field poppy (Papaver rhoeas), S proteins encoded by the stigma component of the S-locus interact with incompatible pollen, resulting in cessation of tip growth. This "self" interaction triggers a Ca(2+)-dependent signaling network, involving programmed cell death (PCD). We previously identified p56, a mitogen-activated protein kinase (MAPK) that is activated during the SI response in incompatible pollen. Here, we show that p56 cross-reacts with AtMPK3, but not with AtMPK4 or salicylic acid-induced protein kinase antibodies. We provide good evidence that a MAPK is involved in initiation of SI-induced PCD in incompatible pollen. SI rapidly reduces pollen viability and the MAPK cascade inhibitor U0126, which prevents the SI-induced activation of p56 in incompatible pollen, "rescues" incompatible pollen, while its negative analog, U0124, does not. This strongly implicates the involvement of a MAPK in SI-mediated loss of pollen viability and cell death. SI also stimulates caspase-3-like (DEVDase) activity and later DNA fragmentation. Both these markers of PCD are significantly reduced by pretreatment with U0126, implicating the involvement of a MAPK in signaling during early PCD. As p56 appears to be the only MAPK activated by SI, our studies imply that p56 could be the MAPK involved in mediating SI-induced PCD.
Li
Shutian
S
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
Samaj
Jozef
J
Franklin-Tong
Vernonica E
VE
D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000378:metabolism; D002070:Butadienes / Q000494:pharmacology; D016923:Cell Death / Q000502:physiology*; D053938:DNA Fragmentation / Q000187:drug effects; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008969:Molecular Sequence Data; D009570:Nitriles / Q000494:pharmacology; D010207:Papaver / Q000201:enzymology* / Q000502:physiology; D010447:Peptide Hydrolases / Q000187:drug effects / Q000378:metabolism; D011058:Pollen / Q000201:enzymology* / Q000502:physiology; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D015398:Signal Transduction / Q000502:physiology*
D029681:Arabidopsis Proteins; D002070:Butadienes; D009570:Nitriles; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; C113580:U 0126; C458516:AtMPK3 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D010447:Peptide Hydrolases; C108711:DEVDase