Nitrogen (N) as well as Phosphorus (P) are key nutrients determining crop productivity.
Legumes have developed strategies to overcome nutrient limitation by, for example, forming
a symbiotic relationship with N-fixing rhizobia and the release of P-mobilizing exudates and
are thus able to grow without supply of N or P fertilizers. The legume-rhizobial symbiosis
starts with root release of isoflavonoids that act as signaling molecules perceived by compatible
bacteria. Subsequently, bacteria release nod factors, which induce signaling cascades
allowing the formation of functional N-fixing nodules. We report here the identification and
functional characterization of a plasma membrane-localized MATE-type transporter (LaMATE2)
involved in the release of genistein from white lupin roots. The LaMATE2 expression in the
root is upregulated under N deficiency as well as low phosphate availability, two nutritional
deficiencies that induce the release of this isoflavonoid. LaMATE2 silencing reduced genistein
efflux and even more the formation of symbiotic nodules, supporting the crucial role of
LaMATE2 in isoflavonoid release and nodulation. Furthermore, silencing of LaMATE2 limited
the P-solubilization activity of lupin root exudates. Transport assays in yeast vesicles
demonstrated that LaMATE2 acts as a proton-driven isoflavonoid transporter.
