Peptide and Amino Acid Transporters Are Differentially Regulated during Seed Development and Germination in Faba Bean

Abstract

Two peptide transporter (PTR) homologs have been isolated from developing seeds of faba bean (Vicia faba). VfPTR1 was shown to be a functional peptide transporter through complementation of a yeast mutant. Expression patterns of VfPTR1 and VfPTR2 as well as of the amino acid permease VfAAP1 (Miranda et al., 2001) were compared throughout seed development and germination. In developing seeds, the highest levels of VfPTR1 transcripts were reached during midcotyledon development, whereas VfAAP1 transcripts were most abundant during early cotyledon development, before the appearance of storage protein gene transcripts, and were detectable until late cotyledon development. During early germination, VfPTR1 mRNA appeared first in cotyledons and later, during seedling growth, also in axes and roots. Expression of VfPTR2 and VfAAP1 was delayed compared with VfPTR1, and was restricted to the nascent organs of the seedlings. Localization of VfPTR1 transcripts showed that this PTR is temporally and spatially regulated during cotyledon development. In germinating seeds, VfPTR1 mRNA was localized in root hairs and root epidermal cells, suggesting a role in nutrient uptake from the soil. In seedling roots, VfPTR1 was repressed by a dipeptide and by an amino acid, whereas nitrate was without influence.

Nitrate transporters and peptide transporters

“…In the past few years, using degenerate primers designed to conserved regions of peptide transporters, homologous genes encoding peptide transporters have been identified in barley [18], Vicia faba [45], and the carnivorous plant, Nepenthes, [46]. The barley scutellar peptide transporter, HvPTR1, is the best characterized plant PTR, as peptide transport in germinating barley grain has been extensively studied using biochemical approaches [18,47,48].…”

AtPTR1 and AtPTR5 Transport Dipeptides in Planta

“…Expression of AtPTR5 in the peptide transport-deficient and His auxotroph yeast (Saccharomyces cerevisiae) strain LR2 showed that, similar to other members of subfamily II, AtPTR5 mediates growth when using selective concentrations of His-Ala (1 mM) as sole source of His ( Fig. 2; Frommer et al, 1994;Rentsch et al, 1995;West et al, 1998;Miranda et al, 2003;Dietrich et al, 2004). Interestingly, the Arabidopsis di-and tripeptide transporters AtPTR1 and AtPTR2 also mediated growth on selective concentrations of His (6 mM), although affinity for His and transport rates seem to be rather low (Frommer et al, 1994;Chiang et al, 2004;Dietrich et al, 2004).…”

“…Several members of subfamily II (see below) and one member of subgroup III (AtPTR3, At5g46050) are confirmed transporters for di-and tripeptides (Karim et al, 2005(Karim et al, , 2007Rentsch et al, 2007). Species with confirmed peptide transporters in subgroup II include Arabidopsis (AtPTR1, AtPTR2), fava bean (VfPTR1), Hakea actities (HaPTR4), and barley (HvPTR1; Frommer et al, 1994;Rentsch et al, 1995;West et al, 1998;Miranda et al, 2003;Dietrich et al, 2004). Subfamily II also contains several noncharacterized genes from Arabidopsis and other species (Fig.…”

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

“…The diurnal and spatial expression profiles of AAP genes are diverse, and further studies are required to unravel their potential roles in the control of amino acid levels in the developing seeds, as recently described for orthologous AAPs in Arabidopsis and pea (Pisum sativum; Weigelt et al, 2008;Sanders et al, 2009). In addition to amino acids, phloem-derived peptides contribute significantly to the nitrogen status and regulate development in developing seeds (Miranda et al, 2003;Li et al, 2009). The diurnal expression of 11 peptide transporter genes points at a tight diurnal control of the nitrogen status in seeds via peptide import (Supplemental Table S3).…”