IBIP seminar

Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

June 13, 2024, 2pm – Amphi 2 (Bât.2bis)

Louis Grillet

Assistant professor in the Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan

Root-secreted molecules shape root architecture and modulate Fe and Cd homeostasis

As sessile organisms, plants cannot evade adverse conditions. One of the mechanism they use to protect themselves, is to secrete metabolites through their roots. These molecules can inhibit the growth of neighboring plants, thereby conferring a competitive advantage. These allelochemicals affect plant growth by mimicking endogenous molecules and triggering existing signaling pathways. We studied one such molecule, 3,4-Dihydroxy-L-phenylalanine (L-DOPA) with a particular interest on its effect on root architecture and on iron (Fe) uptake by roots. L-DOPA is secreted by some legume species and was shown to induce the expression of Fe uptake genes. We aimed at improving our knowledge of the mode of action of this molecule to optimize its application, and find novel applications. We showed that exogenous L-DOPA can increase Fe concentration in plants tissues. We discovered that L-DOPA could promote the tolerance to cadmium (Cd) by decreasing the accumulation of Cd in leaves. This tolerance appears to be mediated by the establishment of a peculiar expression profile of metal homeostasis genes. However, L-DOPA also inhibited plant growth, which is an hindrance to its effective application for either increasing Fe concentration or decreasing Cd accumulation.Surprisingly, the effects of L-DOPA on growth were enhanced under conditions that favors its degradation such as a slightly alkaline pH, and correlated with the formation of melanin, produced through oxidation L-DOPA. The bioactivity of L-DOPA primary oxidation products, 5,6-dihydroxyindole (DHI) and 5,6-dihyroxyindole-2-carboxylic acid (DHICA) was therefore investigated. The two molecules had distinct effects on traits typically affected by L-DOPA: the expression of Fe deficiency genes, root growth and the accumulation of proanthocyanidins. We challenged the assumption that L-DOPA could affect auxin distribution in roots through the formation of these indole compounds, thereby modulating root architecture and Fe uptake.While the mechanisms underlying L-DOPA mode of action remain elusive, we identified novel chemical and molecular mechanisms of toxicity and detoxification of this compound by plants, as well as potential applications.

Contact : stephane.mari@inrae.fr