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The Arabidopsis L-type Amino Acid Transporter-5 (LAT5, At3g19553) was recently studied for its role in developmental responses such as flowering and senescence, under an assumption that it is a polyamine uptake transporter (PUT5). The LATs in Arabidopsis have a wide range of substrates, including amino acids and polyamines. This report extensively studied the organ and tissue-specific expression of the LAT5/PUT5 and investigated its role in mediating amino acid transport. Organ-specific quantitative RT-PCR detected LAT5/PUT5 transcripts in all organs with a relatively higher abundance in the leaves. Tissue-specific expression analysis identified GUS activity in the phloem under the LAT5/PUT5 promoter. In silico analysis identified both amino acid transporter and antiporter domains conserved in the LAT5/PUT5 protein. The physiological role of the LAT5/PUT5 was studied through analyzing a mutant line, lat5-1, under various growth conditions. The mutant lat5-1 seedlings showed increased sensitivity to exogenous leucine in Murashige and Skoog growth medium. In soil, the lat5-1 showed reduced leaf growth and altered nitrogen content in the seeds. In planta radio-labelled leucine uptake studies showed increased accumulation of leucine in the lat5-1 plants compared to the wild type when treated in the dark prior to the isotopic feeding. These studies suggest that LAT5/PUT5 plays a role in mediating amino acid transport.

International audience; Legumes deliver unique functions that are complementary to those of other groups of species (cereals and oil-rich crops), providing many ecosystem services related to nitrogen. However, the choice of grain legumes according to their ability to provide these ecosystem services remains difficult due to a lack of references for a variety of species. During two legume – wheat successions established between 2014 and 2017, five nitrogen pools were measured, and considered as proxies of nitrogen functions supporting ecosystem services and dis-services. Nitrogen pools were analyzed together with several of their explanatory shoot and root characteristics (i.e. plant traits and properties). For the first time, a wide range of grain legumes could be characterized by their contrasted functional profiles relative to nitrogen. For each species, synergies and trade-offs between the different nitrogen functions were highlighted and related to the explanatory plant characteristics. Shoot and root characteristics explained 76.1% of the variability of nitrogen functions among legumes species. Chickpea, common bean, and soybean had high capacity to take up soil nitrogen during their growth cycles, reducing the risk of nitrogen losses after their harvest. These species were characterized by a high root lateral expansion rate and their capacity to invest a large proportion of belowground biomass in nodules. Conversely, common vetch, faba bean, lentil, pea and Narbonne vetch, were less able to take up soil nitrogen, with higher risks of nitrogen losses, but these species induced high amounts of nitrogen in the following wheat crop and were characterized by high crop residue nitrogen concentration. Larger amounts of nitrogen fixed and exported in seeds were measured for species characterized by high shoot dry matter, high nitrogen harvest index, high seed nitrogen concentration, and large seeds. Hence, this study should facilitate the selection of legume species according to the expected objectives.

International audience; The aim of this study was to investigate the role of ASN3-encoded asparagine synthetase (AS, EC 6.3.5.4) during vegetative growth, seed development and germination of Arabidopsis thaliana. Phenotypic analysis of knockout (asn3-1) and knockdown (asn3-2) T-DNA insertion mutants for the ASN3 gene (At5g10240) demonstrated wild-type contents of asparagine synthetase protein, chlorophyll and ammonium in green leaves at 35 days after sowing. In situ hybridization localized ASN3 mRNA to phloem companion cells of vasculature. Young siliques of the asn3-1 knockout line showed a decrease in asparagine but an increase in glutamate. The seeds of asn3-1 and asn3-2 displayed a wild-type nitrogen status expressed as total nitrogen content, indicating that the repression of ASN3 expression had only a limited effect on mature seeds. An analysis of amino acid labeling of seeds imbibed with (N-15) ammonium for 24 h revealed that asn3-1 seeds contained 20% less total asparagine while N-15-labeled asparagine ((2-N-15)asparagine, (4-N-15)asparagine and (2,4-N-15)asparagine) increased by 12% compared to wild-type seeds. The data indicate a fine regulation of asparagine synthesis and hydrolysis in Arabidopsis seeds.