Fig. 3.

A plant metabolic link between adaption to drought and reduced N stress. Allantoin catabolism is restricted in drought-stressed plants. Allantoin accumulation both induces de novo synthesis of ABA and activates ABA from the inactive glycosylated form. Regulation of these processes may prevent loss of N as NH₃ gas when carbon skeletons are in short supply. In contrast, under low N conditions, allantoin is catabolized (Melino et al., 2018) and recycled to NH₃ which can be reduced by N-assimilatory enzymes or instead serve as a cheap N storage form for translocation to the grain where it represents a significant portion of the soluble N pool (Casartelli et al., 2019).