AtPTR1 and AtPTR5 Transport Dipeptides in Planta

Abstract

Transporters for di-and tripeptides belong to the large and poorly characterized PTR/NRT1 (peptide transporter/nitrate transporter 1) family. A new member of this gene family, AtPTR5, was isolated from Arabidopsis (Arabidopsis thaliana). Expression of AtPTR5 was analyzed and compared with tissue specificity of the closely related AtPTR1 to discern their roles in planta. Both transporters facilitate transport of dipeptides with high affinity and are localized at the plasma membrane. Mutants, double mutants, and overexpressing lines were exposed to several dipeptides, including toxic peptides, to analyze how the modified transporter expression affects pollen germination, growth of pollen tubes, root, and shoot. Analysis of atptr5 mutants and AtPTR5-overexpressing lines showed that AtPTR5 facilitates peptide transport into germinating pollen and possibly into maturating pollen, ovules, and seeds. In contrast, AtPTR1 plays a role in uptake of peptides by roots indicated by reduced nitrogen (N) levels and reduced growth of atptr1 mutants on medium with dipeptides as the sole N source. Furthermore, overexpression of AtPTR5 resulted in enhanced shoot growth and increased N content. The function in peptide uptake was further confirmed with toxic peptides, which inhibited growth. The results show that closely related members of the PTR/NRT1 family have different functions in planta. This study also provides evidence that the use of organic N is not restricted to amino acids, but that dipeptides should be considered as a N source and transport form in plants.

A novel fungal family of oligopeptide transporters identified by functional metatranscriptomics of soil eukaryotes

“…Furthermore, the calculated K m of EnvFOT-Fp for Tyr-Ala (23 mM) is lower than affinity constants reported for plant peptide transporters of the peptide transport family as estimated using Xenopus oocytes (for example, 130-160 mM for the root-expressed AtPTR5; Komarova et al, 2008, and references therein). As for the concentration of di/tripeptides in the soil solution, no quantitative data are available to our knowledge.…”

“…Furthermore, heterologous expression in Xenopus oocytes allowed us to demonstrate that at least EnvFOT-F could transport L-cysteine. The transport of additional nitrogenous compounds had already been documented for other eukaryotic di/tripeptide transporters such as the yeast dal5p known to transport allantoate and ureidosuccinate (Cai et al, 2007), the Arabidopsis PTR2-B and PTR1 shown to transport histidine (Frommer et al, 1994;Komarova et al, 2008) and the human hPAT1 that transports both amino acids and a few dipeptides (Frølund et al, 2010). It is therefore possible that the true range of N compounds transported by FOT transporters extends beyond di/tripeptides and cysteine.…”

The plasma membrane proteome of Medicago truncatula roots as modified by arbuscular mycorrhizal symbiosis

“…As inferred from the transcriptional activation of the corresponding genes in cells containing arbuscules (Table S3), both MtPTR1 and MtSPT13 are likely to have a role at this symbiotic interface. According to characterization of the PMlocalized PTR1 in Arabidopsis (Komorova et al 2008(Komorova et al , 2012, MtPTR1 may function as a di-and tripeptide transporter. Noticeably, the putative dipeptide transporter RiPTR2 has been identified in R. irregularis (Belmondo et al 2014).…”

High-resolution metabolic mapping of cell types in plant roots

“…Although small peptides (e.g., DPs and tripeptides) are considered as a nitrogen source for plant growth, data regarding these molecules, their abundance, and their roles in plants are limited (25). Nontargeted analysis of extracts derived from the five sorted cell-type populations suggested the accumulation of DPs in specific cell types.…”