<i>Mtha</i>1, a Plasma Membrane H⁺‐ATPase Gene from <i>Medicago truncatula,</i> Shows Arbuscule‐Specific Induced Expression in Mycorrhizal Tissue

Abstract

Abstract: Transport processes between plant and fungal cells are key elements in arbuscular mycorrhiza (AM), where H + ‐ATPases are considered to be involved in active uptake of nutrients from the symbiotic interface. Genes encoding H + ‐ATPases were identified in the genome of Medicago truncatula and three cDNA fragments of the H + ‐ATPase gene family ( Mtha 1 ‐ 3) were obtained by RT‐PCR using RNA from M. truncatula mycorrhizal roots as template. While Mtha 2 and Mtha 3 appeared to be constitutively expressed in roots and unaffected by AM development, transcripts of Mtha 1 could only be detected in AM tissues and not in controls. Further analyses by RT‐PCR revealed that Mtha 1 transcripts are not detectable in shoots and phosphate availability did not affect RNA accumulation of the gene. Localization of transcripts by in situ hybridization on AM tissues showed that Mtha 1 RNA accumulates only in cells containing fungal arbuscules. This is the first report of arbuscule‐specific induced expression of a plant H + ‐ATPase gene in mycorrhizal tissues.