Poster: Signaling, cell-to-cell

Abs # 423: Differential Interactions of the Tomato Stress Responsive MAPKs, LeMPK1/2 and LeMPK3 with four LeMKKs

Presenter:	Yalamanchili, Roopa Devi, yalamanchili@biol.sc.edu
Authors	Yalamanchili, Roopa Devi (A)   Stratmann, Johannes W (A)
Affiliations:	(A): University Of South Carolina

Among plant responses to biotic and abiotic stresses, is the induction of a group of protein kinases, termed mitogen activated protein kinases (MAPKs). Here, we provide evidence that specific MAPKs are activated by various stresses in L. peruvianum suspension-cultured cells. We tested elicitors that are released in response to insect herbivory(systemin), and fungal pathogen attack (oligosaccharide elicitors such as chitin, chitosan, β-glucan, and PGA). We tested heat, UV-B and UV-C radiation as abiotic stresses. Earlier we cloned three LeMPKs and specific antibodies were raised against peptides corresponding to the N-termini. Using immunocomplex kinase assays, we have found that the biotic stress signals activated LeMPK1 and LeMPK2, while the abiotic stresses activated LeMPK3 in addition to LeMPK1 and LeMPK2. To identify the upstream activators of these LeMPKs, we have cloned three MAPKKs from a tomato cDNA library prepared from plants overexpressing prosystemin. We used LeMKK3, LeMKK4 and LeMKK5 along with the previously identified stress-responsive tomato MAPKK, tMEK2 (Xing et al, 2001). Through yeast two hybrid analysis we found that tMEK2, LeMKK3 and LeMKK4 interacted strongly with LeMPK1 and LeMPK2. In contrast, LeMKK5 interacted with LeMPK3 but not with LeMPK1 and LeMPK2. Taken together, these results indicate that LeMPK1/2 and LeMPK3 are activated by different MAPKKs. This is consistent with the differential responsiveness of LeMPK1/2 and LeMPK3 to biotic and abiotic stress signals, respectively. The next step will be to confirm LeMKK - LeMPK interactions in vivo. For this we will use a protoplast transient gene expression system.