Molecular cloning and functional analysis of two phosphate transporter genes from Rhizopogon luteolus and Leucocortinarius bulbiger, two ectomycorrhizal fungi of Pinus tabulaeformis

Abstract

Inorganic phosphorus (Pi) is essential for plant growth, and phosphate (P) deficiency is a primary limiting factor in Pinus tabulaeformis development in northern China. P acquisition in mycorrhizal plants is highly dependent on the activities of phosphate transporters of their root-associated fungi. In the current study, two phosphate transporter genes, RlPT and LbPT, were isolated from Rhizopogon luteolus and Leucocortinarius bulbiger, respectively, two ectomycorrhizal fungi forming symbiotic interactions with the P. tabulaeformis. Phylogenetic analysis suggested that the sequence of the phosphate transporter of L. bulbiger is most closely related to a phosphate transporter of Hebeloma cylindrosporum, whereas the phosphate transporter of R. luteolus is most closely related to that of Piloderma croceum. The subcellular localization indicated that RlPT and LbPT were expressed in the plasma membrane. The complementation assay in yeast indicated that both RlPT and LbPT partially compensated for the absence of phosphate transporter activity in the MB192 yeast strain, with a K m value of 57.90 μmol/L Pi for RlPT and 35.87 μmol/L Pi for LbPT. qPCR analysis revealed that RlPT and LbPT were significantly up-regulated at lower P availability, which may enhance P uptake and transport under Pi starvation. Our results suggest that RlPT and LbPT presumably play a key role in Pi acquisition by P. tabulaeformis via ectomycorrhizal fungi.

The Hebeloma cylindrosporum HcPT2 Pi transporter plays a key role in ectomycorrhizal symbiosis

“…a). Such a role in Pi uptake has already been ascribed to HcPT2 (Tatry et al ., ) as well as for other H + :Pi symporters whose proteins or transcripts were detected in ECM (Garcia et al ., ; Wang et al ., ; Zheng et al ., ) or arbuscular mycorrhizal (AM) (Harrison & van Buuren, ; Xie et al ., ) fungi. The fact that transgenic lines overexpressing HcPT2 were unaffected in their Pi uptake could be due to a saturation of the Pi transport in nonlimiting Pi concentrations.…”

“…The search for homologous genes in available genomes of ECM fungi shows that the vast majority of Basidiomycete species display only H + :Pi symporters, contrary to the Ascomycete Tuber melanosporum, which harbors both Pi:Na + and H + :Pi symporters (Casieri et al, 2013;Hacquard et al, 2013;Nehls & Plassard, 2018). To date, only two P transporters from Hebeloma cylindrosporum (HcPT1.1 and HcPT2), one from Boletus edulis (BePT), one from Rhizopogon luteolus (RlPT) and one from Leucocortinarius bulbiger (LbPT) have been characterized as high-affinity H + :Pi transporters (Tatry et al, 2009;Wang et al, 2014;Zheng et al, 2016). Recent analysis of the H. cylindrosporum genome revealed another putative H + :Pi transporter closely related to HcPT1.1 and called HcPT1.2 (Casieri et al, 2013;Kohler et al, 2015).…”

Role of mycorrhizas and root exudates in plant uptake of soil nutrients (calcium, iron, magnesium, and potassium): has the puzzle been completely solved?

“…Similarly to HcPT1.1, upregulation by low Pi has been found for other H + /Pi transporters in Tricholoma spp. (Kothe et al., 2002), Boletus edulis (Wang, Li, et al., 2014; Wang, Yu, et al., 2014), Rhizopogon luteolus (Zheng et al., 2016), and Leucocortinarius bulbiger (Zheng et al., 2016).…”

Presidential address: recent advance of mycorrhizal research in China

“…Liu et al (2015) found that drought stress upregulated the level of R. intraradices and soybean mitogen-activated protein kinase (MAPK) transcripts in mycorrhizal soybean roots, indicating the possibility of a molecular dialogue between AM fungus and host plant and suggesting that they might cooperate to improve soybean’s resistance to drought stress. Concurrently, in terms of nutrient absorption, some studies investigated the mycorrhiza-regulated phosphate transporters in host plants Astragalus sinicus (Xie et al 2013), Oryza sativa (Sun et al 2012), P. tabulaeformis (Zheng et al 2016a), pepper and tobacco (Chen et al 2007), and reciprocal transportation of carbon and phosphorus amongst plants ( Zea mays and Medicago sativa ), Rhizophagus irregularis and phosphate-solubilising bacterium (Zhang et al 2016; Wang et al 2016a). Wang et al (2014) demonstrated that H + -ATPase played a key role in energising the periarbuscular membrane, thereby facilitating nutrient exchange in arbusculated rice and Medicago truncatula cells.…”