A H+-ATPase That Energizes Nutrient Uptake during Mycorrhizal Symbioses in Rice and Medicago truncatula      

Abstract

Most plant species form symbioses with arbuscular mycorrhizal (AM) fungi, which facilitate the uptake of mineral nutrients such as phosphate from the soil. Several transporters, particularly proton-coupled phosphate transporters, have been identified on both the plant and fungal membranes and contribute to delivering phosphate from fungi to plants. The mechanism of nutrient exchange has been studied in plants during mycorrhizal colonization, but the source of the electrochemical proton gradient that drives nutrient exchange is not known. Here, we show that plasma membrane H + -ATPases that are specifically induced in arbuscule-containing cells are required for enhanced proton pumping activity in membrane vesicles from AM-colonized roots of rice (Oryza sativa) and Medicago truncatula. Mutation of the H + -ATPases reduced arbuscule size and impaired nutrient uptake by the host plant through the mycorrhizal symbiosis. Overexpression of the H + -ATPase Os-HA1 increased both phosphate uptake and the plasma membrane potential, suggesting that this H + -ATPase plays a key role in energizing the periarbuscular membrane, thereby facilitating nutrient exchange in arbusculated plant cells.

The Root Hair “Infectome” of Medicago truncatula Uncovers Changes in Cell Cycle Genes and Reveals a Requirement for Auxin Signaling in Rhizobial Infection

“…One such H + -ATPase, HA1, was induced by both S. meliloti and Nod factors. Previously, HA1 was thought to be expressed only in arbusculated cells (Krajinski et al, 2002) where it is required for phosphate uptake during mycorrhization (Krajinski et al, 2014;Wang et al, 2014). Its expression during infection suggests that HA1 may also have a role in auxin-mediated acid-induced cell wall growth during rhizobial infection and arbuscule formation.…”

Diet of Arbuscular Mycorrhizal Fungi: Bread and Butter?

“…The highly branched arbuscules appear ideally suited for lipid absorption, in particular, because the symbiotic interface is extremely narrow and essentially comprises only a thin fungal cell wall between the membranes of the two partners [71]. The periarbuscular space is acidified by H + [ 2 0 8 _ T D $ D I F F ] -ATPases which energize mineral nutrient uptake by the plant [72][73][74][75]. At the same time, the low pH would lead to protonation of free FAs, which have a pKa in an aqueous environment of 4.8 [76].…”

Medicago truncatula Mtha1-2 mutants loose metabolic responses to mycorrhizal colonization

“…5 The recent identification of M. truncatula mutants defective in the symbiotic transfer of nutrients across the periarbuscular space allows us now to study the impact of fungal colonization independent of the improved nutrition of the plant. 1,6 The lack of functional MtHA1 proteins is leading to the incapability of phosphate uptake, and presumably also other ions, from the periarbuscular space. In accordance with this assumption, we did not observe a positive growth response of mycorrhizal mtha1-2 mutant plants.…”