Salt stress-induced proline transporters and salt stress-repressed broad specificity amino acid permeases identified by suppression of a yeast amino acid permease-targeting mutant.

Abstract

A yeast mutant lacking SHRS, a protein specifically required for correct targeting of plasma membrane amino acid permeases, was used to study the targeting of plant transportem and as a tool to isolate new SHR3-independent amino acid transportem. For this purpose, an shr3 mutant was transformed with an Arabidopsis cDNA library. Thirty-four clones were capable of growth under selective conditions, but none showed homology with SHR3. However, genes encoding eight different amino acid transportem belonging to three different transporter families were isolated. Five of these are members of the general amino acid permease (AAP) gene family, one is a member of the NTR family, encoding an oligopeptide transporter, and two belong to a new class of transporter genes. A functional analysis of the latter two genes revealed that they encode specific proline transporters (ProT) that are distantly related to the AAP gene family. PfoTT was found to be expressed in all organs, but highest levels were found in roots, stems, and flowers. Expression in flowers was highest in the floral stalk phloem that enters the carpels and was downregulated after fertilization, indicating a specific role in supplying the ovules with proline. ProT2 transcripts were found ubiquitously throughout the plant, but expression was strongly induced under water or salt stress, implying that ProT2 plays an important role in nitrogen distribution during water stress, unlike members of the AAPgene family whose expression was repressed under the same conditions. These results corroborate the general finding that under water stress, amino acid export is impaired whereas proline export is increased.

The 'permeome' of the malaria parasite: an overview of the membrane transport proteins of Plasmodium falciparum

“…The other three (PFB0435c, PFE0775c and PF11_0334) are members of the neurotransmitter:Na + symporter (NSS) family. Proteins of the AAAP family are known to mediate the transport of a specific amino acid (for example, the proline permease of Arabidopsis thaliana [50]), or of a group of similar amino acids (for example, the neutral amino-acid permease of Neurospora crassa [51]), while several members exhibit very broad specificities, transporting all naturally occurring amino acids (for example, the general amino-acid transporter of A. thaliana [52]). AAAP proteins are found in yeast, protozoans, plants and animals, and transport is usually either H + - and/or Na + -dependent [53-55].…”

A mutation in amino acid permease AAP6 reduces the amino acid content of the Arabidopsis sieve elements but leaves aphid herbivores unaffected

“…It has been reported that the AAP6 gene encodes a transporter of aspartic acid as well as other neutral and acidic amino acids (Rentsch et al , 1996; Fischer et al , 2002; Okumoto et al , 2002). In the present study, SE aspartic acid concentration was decreased by 80% in the aap6 mutant.…”

Isolation and characterization of LHT-type plant amino acid transporter gene from Panax ginseng Meyer

“…ProT1 was found to be expressed in all organs of Arabidopsis, but highest levels were found in roots, stems, and flowers [21].…”

“…ProT1 and ProT2 are widely expressed proline-specific amino acid transporters in Arabidopsis, they respond differentially to changes in water and salinity stress. ProT2 expression was strongly induced under water or salinity stress [21], implying that PgLHT are similar to ProT2 and play an important role in nitrogen distribution during water stress.…”