Characterization of the binding site for the protein elicitor PeaT1 on tobacco plasma membrane.

The protein elicitor,PeaT1 derived from Alternaria tenuissima has been found to trigger systemic acquired resistance in plant.The present investigation was aimed to study the molecular mechanisms of PeaT1 in disease resistance.It was found that the transcription level of PR-1a gene in tobacco suspension-cultured cells was the highest after 8 hours of incubation with PeaT1 at the concentration of 20 μg/mL.Similarly,the expression level of acidic PR protein was also observed in tobacco leaves treated with same concentration of PeaT1.It was revealed that FITC labeled PeaT1 could bind with surface of tobacco suspension-cultured cells under Confocal Scanning Laser microscope.Similarly,it was noticed that PeaT1 could bind with protoplasts of tobacco cells when immunofluorescence method was used.Furthermore,two proteins of about 20 kDa and 30 kDa interacting with 125I-PeaT1 were identified on tobacco plasma membranes using the homobifunctional cross-linking reagent BS3.The sensitivity of binding sites to proteinase and heat treatment further supported the proteinaceous nature of interacting molecules on plasma membrane.The work reports the existence of binding site with many characteristics of expected elicitor receptor.