Lateral root branching promoted by ammonia borane-dependent H2

Molecular hydrogen (H₂) has been shown to have several cellular benefits, most notably serving as an antioxidant. Its effects in humans and plants have been primarily assayed using hydrogen-rich water (HRW, produced by bubbling H₂ into water), but slower, more persistent release of H₂ has been demonstrated from solid ammonia borane (NH₃BH₃). Here, Wang et al. examined how ammonia borane affects root growth, using hydroponically grown tomatoes treated with ammonia borane (AB). Upon treatment with AB, roots showed an increase in expression level of several genes involved in the synthesis of phytomelatonin and an accompanying increase in phytomelatonin levels. The AB-promoted increase in root branching is suppressed by an inhibitor of phytomelatonin synthesis, and root branching is enhanced by exogenous phytomelatonin treatment, suggesting that the effects of AB are mediated through phytomelatonin. AB or phytomelatonin further led to an increase in expression on several auxin-signaling genes, suggesting that auxin has a role in this response. (Summary by Mary Williams @PlantTeaching) Plant Physiol. 10.1093/plphys/kiad595