Fig. 7.

Schematic model for how allantoin activates JA responses in Arabidopsis. Accumulation of allantoin causes enhanced ABA levels through de novo synthesis from carotenoids and/or hydrolytic conversion from inactive ABA glucosides, thereby activating ABA-dependent JA responses mediated by MYC2. The effect of allantoin on de novo synthesis may be indirect due to positive feedback of ABA released from the inactive pool (Watanabe et al., 2014b ). The open arrows indicate metabolic routes, and lines with arrows and bar ends represent positive and negative causal relationships, respectively.