Abstract

Mineral nutrients, such as manganese (Mn) and iron (Fe), play essential roles in many biological processes in plants but their over-enrichment is harmful for the metabolism. Metal tolerance proteins (MTPs) are involved in cellular Mn and Fe homeostasis. However, the transporter responsible for the transport of Mn in wheat is unknown. In our study, TuMTP8, a Mn-CDF transporter from diploid wheat (Triticum urartu), was identified. Expression ofTuMTP8in yeast strains of Δccc1and Δsmf1andArabidopsisconferred tolerance to elevated Mn and Fe, but not to other metals (zinc, cobalt, copper, nickel, or cadmium). Compared with TuVIT1 (vacuole Fe transporter), TuMTP8 shows a significantly higher proportion in Mn transport and a smaller proportion in Fe transport. The transient analysis in tobacco epidermal cells revealed that TuMTP8 localizes to vacuolar membrane. The highest transcript levels ofTuMTP8were in the sheath of the oldest leaf and the awn, suggesting that TuMTP8 sequesters excess Mn into the vacuole in these organs, away from more sensitive tissues. These findings indicate thatTuMTP8, a tonoplast-localized Mn/Fe transporter, functions as a primary balancer to regulate Mn distribution inT. urartuunder elevated Mn conditions and participates in the intracellular transport and storage of excess Mn as a detoxification mechanism, thereby conferring Mn tolerance.Keywords:CDF (cation diffusion facilitator);diploid wheat;transporter