Plant defense activators potentiate the generation of elicitor-responsive photon emission in rice

Ultraweak photon emission from rice induced by an elicitor was measured to estimate the influence of pretreated plant defense activators on elicitor-responsive photon emission. Rice leaf segments treated with an elicitor transiently generated relatively high levels of elicitor-responsive photon emission. Pretreatment with plant defense activators increased elicitor-responsive photon emission. This increase was also observed in suspension-cultured rice cells. Prolonged pretreatment allowed the plant defense activators to accelerate photon generation and to act at lower doses. The activators themselves did not induce any marked photon emission in rice leaf segments or cells. The spectral compositions of the increased and nonincreased elicitor-responsive photon emissions from rice cells were almost the same. Therefore, plant defense activators probably potentiate the generation of elicitor-responsive photon emission itself. The elicitor-responsive expression of the PBZ1 gene was strongly enhanced by pretreatment of rice cells with plant defense activators, when elicitor-responsive photon emission was also enhanced. We could not identify a significant correlation between the degree of photon emission enhancement and the potentiation of PBZ1 expression with each treatment. However, the results indicate that the generation of elicitor-responsive photon emission is potentiated when rice cells are primed for disease resistance by plant defense activators.