P-362 - Effects of strigolactone analog 4BD on disease resistance in rice.

Strigolactones (SLs) are plant hormones that inhibit shoot branching and are involved in interactions between plants and other organisms, such as arbuscular mycorrhizal fungi and parasitic weeds. Recently, it has been reported that SLs positively regulate plant disease resistance. In this study, we used the synthetic SL analog 4BD, which is easier to synthesize than other analogs and exhibits a stronger effect on shoot branching in rice. First, we demonstrated in vitro that 4BD promotes the interaction between its receptor D14 and the signaling factor D3, similar to the well-known SL analog GR24. Next, we found that treatment with 4BD alone did not affect rice blast resistance compared to the control. We then analyzed the effect of 4BD on systemic acquired resistance (SAR), which is SA-mediated disease resistance. When SAR inducer BIT was applied after 4BD pretreatment, disease resistance and the expression of marker genes were enhanced compared to BIT treatment alone. However, this effect of 4BD pretreatment was not observed in the SL signaling-deficient mutant d3. These results suggest that the activation of SL signaling by 4BD pretreatment does not directly activate the immune response in rice but rather induces a priming state in the plant.