Solanum lycopersicon MAPK LeMPK3 plays a vital role in tomato defense responses. TAB2 was shown to interact with LeMPK3. In this project, the function of the genes in defense pathways that involve SA and FB1 have been studied. While LeMPK3 was up-regulated, TAB2 was not, suggesting that TAB2 is probably not involved in LeMPK3 pathway. LeMPK3 is an ERK-type MAP kinase. The increased expression of LeMPK3 and SA or FB1 responsive genes was not significantly altered by an ERK inhibitor, suggesting that LeMPK3 may not be involved in SA-triggered PR1 and FB1-triggered PDF1.2 expression. The effect of FB1, SA and the ERK inhibitor treatment on the cell death of tomato leaves was also studied. ERK inhibitor reversed the cell death induced by SA and FB1, suggesting that ERK-type MAPKs could be involved in SA- and FB1-induced cell death process. The full length of the LeMPK3MUT was generated.