Involvement of JA and reactive oxygen species in production of phytoalexins in suspension-cultured rice cells

Abstract

In suspension-cultured rice cells, a chitin elicitor induces production of phytoalexins such as momilactones and phytocassanes. We reported that jasmonic acid (JA) plays an important role in the elicitor-induced phytoalexin production in the rice cells. Although exogenous JA induced phytoalexin production, the levels of phytoalexins were much lower than those in the elicited rice cells. The elicitor induced production of reactive oxygen species (ROS) including H₂O₂. However, exogenous H₂O₂ exhibited no effect on phytoalexin production. In this study, we found that treatment with a mixture of JA (500 μM) and H₂O₂ (10 μM) induced production of momilactones at the same level as that in the elicited rice cells, but that the same treatment induced production of phytocassanes weakly. These results suggest that both JA and ROS are involved in production of momilactones, and that regulatory mechanisms for production of momilactones are different from that for production of phytocassanes.