Structure and Expression Profile of the Phosphate Pht1 Transporter Gene Family in Mycorrhizal Populus trichocarpa    

Abstract

Gene networks involved in inorganic phosphate (Pi) acquisition and homeostasis in woody perennial species able to form mycorrhizal symbioses are poorly known. Here, we describe the features of the 12 genes coding for Pi transporters of the Pht1 family in poplar (Populus trichocarpa). Individual Pht1 transporters play distinct roles in acquiring and translocating Pi in different tissues of mycorrhizal and nonmycorrhizal poplar during different growth conditions and developmental stages. Pi starvation triggered the up-regulation of most members of the Pht1 family, especially PtPT9 and PtPT11. PtPT9 and PtPT12 showed a striking up-regulation in ectomycorrhizas and endomycorrhizas, whereas PtPT1 and PtPT11 were strongly down-regulated. PtPT10 transcripts were highly abundant in arbuscular mycorrhiza (AM) roots only. PtPT8 and PtPT10 are phylogenetically associated to the AM-inducible Pht1 subfamily I. The analysis of promoter sequences revealed conserved motifs similar to other AM-inducible orthologs in PtPT10 only. To gain more insight into gene regulatory mechanisms governing the AM symbiosis in woody plant species, the activation of the poplar PtPT10 promoter was investigated and detected in AM of potato (Solanum tuberosum) roots. These results indicated that the regulation of AM-inducible Pi transporter genes is conserved between perennial woody and herbaceous plant species. Moreover, poplar has developed an alternative Pi uptake pathway distinct from AM plants, allowing ectomycorrhizal poplar to recruit PtPT9 and PtPT12 to cope with limiting Pi concentrations in forest soils.

Nonredundant Regulation of Rice Arbuscular Mycorrhizal Symbiosis by Two Members of the PHOSPHATE TRANSPORTER1 Gene Family

“…Phylogenetic lineages are colored and marked A to E for visual emphasis. (Loth-Pereda et al, 2011), suggesting PT8 is a pseudogene. Consistently, the predicted PT8 protein clusters at a distance to the expressed proteins within the PT11 lineage ( Figure 1C, lineage B).…”

Arbuscular Mycorrhizal Symbiosis Requires a Phosphate Transceptor in the Gigaspora margarita Fungal Symbiont

“…Once the phosphate from the intraradical mycelia is released into the periarbuscular space (PAS), the plant imports it into root cells via the expressed mycorrhiza-specific PTs located in the periarbuscular membrane (PAM) (Harrison et al, 2002). These PTs expressing in arbuscule-containing cells have recently been functionally characterized in AM symbionts of potato, legumes, rice, and poplar (Rausch et al, 2001, Javot et al, 2007, Loth-Pereda et al, 2011and Yang et al, 2012. Similarly, AM fungi essentially contain phosphate transporter genes; for example, GvPT, GiPT, and GmosPT genes have been isolated from the AM fungi Glomus versiforme, Rhizophagus irregularis, and Funneliformis mosseae, respectively ( Harrison and van Buuren, 1995, Maldonado-Mendoza et al, 2001and Benedetto et al, 2005.…”

Fungal and Plant Tools for the Uptake of Nutrients in Arbuscular Mycorrhizas

“…The release of Pi within the root cortex is accompanied by a significant upregulation of plant Pi transporters which have been identified in the following species: Medicago (Harrison et al, 2002;Javot et al, 2007), rice (Paszkowski et al, 2002), Lotus (Guether et al, 2009;Volpe et al, 2015), Astragalus sinicus (Xie et al, 2013), potato (Nagy et al, 2005), maize (Nagy et al, 2006), various cereals (Glassop et al, 2005), tomato (Nagy et al 2005;Balestrini et al, 2007;Xu et al, 2007), poplar (Loth-Pereda et al, 2011) sorghum and flax (Walder et al, 2015). These transporters belong to the PHT1 family of Pi transporters and they show an amino acid sequence conserved from fungi to plants.…”