The Arabidopsis L-Type Amino Acid Transporter 5 (LAT5/PUT5) Is Expressed in the Phloem and Alters Seed Nitrogen Content When Knocked Out
Rowshon A. Begam | Jayne D’Entremont | Allen Good
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, <i>lat5-1</i>, under various growth conditions. The mutant <i>lat5-1</i> seedlings showed increased sensitivity to exogenous leucine in Murashige and Skoog growth medium. In soil, the <i>lat5-1</i> 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 <i>lat5-1</i> 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.
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