Abstract
Wheat grain protein content and composition are important for its end-use quality. Protein synthesis during the grain filling phase is supported by the amino acids remobilized from the vegetative tissue, the process in which both amino acid importers and exporters are expected to be involved. Previous studies identified amino acid importers that might function in the amino acid remobilization in wheat. However, the amino acid exporters involved in this process have been unexplored so far. In this study, we have curated the Usually Multiple Amino acids Move In and out Transporter (UMAMIT) family of transporters in wheat. As expected, the majority of UMAMITs were found as triads in the A, B, and D genomes of wheat. Expression analysis using publicly available data sets identified groups of TaUMAMITs expressed in root, leaf, spike, stem and grain tissues, many of which were temporarily regulated. Strong expression of TaUMAMITs was detected in the late senescing leaves and transfer cells in grains, both of which are the expected site of apoplastic amino acid transport during grain filling. Biochemical characterization of selected TaUMAMITs revealed that TaUMAMIT17 shows a strong amino acid export activity and might play a role in amino acid transfer to the grains.
Highlights
Wheat grain protein content and composition are important for its end-use quality
Cellular amino acid importers belonging to the families of Amino Acid Permeases (AAPs), Lysine and Histidine Transporters (LHTs), Cationic Amino acid Transporters (CATs), Proline and GABA transporters (ProT/GABAT), Auxin Transporters (AUXs), and Aromatic and Neutral amino acid transporters (ANTs) have been identified, and for some transporters, their physiological roles have been identified, including amino acid export from source leaves[1], amino acid loading to the seeds[2,3,4], xylem-to-phloem amino acid transfer[5], amino acid transport from the nodules[6], and root uptake of amino acids[1,7,8,9,10]
These transporters belong to amino acid -polyamine-choline (APC) family and the amino acid/auxin permease (AAAP) family, and most of them function as amino acid-proton s ymporters[11,12]
Summary
Wheat grain protein content and composition are important for its end-use quality. Protein synthesis during the grain filling phase is supported by the amino acids remobilized from the vegetative tissue, the process in which both amino acid importers and exporters are expected to be involved. We report the identification of potential amino acid transporters belonging to the UMAMIT family in wheat.
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