The function of the Medicago truncatula ZIP transporter MtZIP14 is linked to arbuscular mycorrhizal fungal colonisation

Abstract

Soil micronutrient availability, including zinc (Zn), is a limiting factor for crop yield. Arbuscular mycorrhizal (AM) fungi can improve host plant growth and nutrition through the mycorrhizal pathway of nutrient uptake. Although the physiology of Zn uptake through the mycorrhizal pathway is well established, the identity of the related molecular components are unknown. Here, RNA-seq analysis was used to identify genes differentially-regulated by AM colonisation and soil Zn concentration in roots of Medicago truncatula. The putative Zn transporter gene MtZIP14 was markedly up-regulated in Medicago truncatula roots when colonised by Rhizophagus irregularis. MtZIP14 restored yeast growth under low Zn availability. Loss-of-function mutant plants (mtzip14) had reduced shoot biomass compared to the wild-type when colonised by AM fungi and grown under low and sufficient soil Zn concentration; at high soil Zn concentration, there were no genotypic differences in shoot biomass. Vesicular and arbuscular colonisation of roots was lower in the mtzip14 plants regardless of soil Zn concentration. We propose that MtZIP14 is linked to AM colonisation in M. truncatula plants, with the possibility that MtZIP14 function with AM colonisation is linked to soil or plant Zn nutrition. This article is protected by copyright. All rights reserved.