The Medicago truncatula Vacuolar iron Transporter-Like proteins VTL4 and VTL8 deliver iron to rhizobium bacteria at different stages of the infection process

Walton, Jennifer H., Kontra‐Kováts, Gyöngyi, Green, Robert T., Domonkos, Ágota, Horváth, Beatrix, Brear, Ella M., Franceschetti, Marina, Kaló, Péter and Balk, Janneke (2020) The Medicago truncatula Vacuolar iron Transporter-Like proteins VTL4 and VTL8 deliver iron to rhizobium bacteria at different stages of the infection process. New Phytologist, 228 (2). pp. 651-666. ISSN 0028-646X

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Abstract

The symbiotic relationship between legumes and rhizobium bacteria in root nodules has a high demand for iron, and questions remain regarding which transporters are involved. Here, we characterize two nodule-specific Vacuolar iron Transporter-Like (VTL) proteins in Medicago truncatula. Localization of fluorescent fusion proteins and mutant studies were carried out to correlate with existing RNA-seq data showing differential expression of VTL4 and VTL8 during early and late infection, respectively. The vtl4 insertion lines showed decreased nitrogen fixation capacity associated with more immature nodules and less elongated bacteroids. A mutant line lacking the tandemly-arranged VTL4–VTL8 genes, named 13U, was unable to develop functional nodules and failed to fix nitrogen, which was almost fully restored by expression of VTL8 alone. Using a newly developed lux reporter to monitor iron status of the bacteroids, a moderate decrease in luminescence signal was observed in vtl4 mutant nodules and a strong decrease in 13U nodules. Iron transport capability of VTL4 and VTL8 was shown by yeast complementation. These data indicate that VTL8, the closest homologue of SEN1 in Lotus japonicus, is the main route for delivering iron to symbiotic rhizobia. We propose that a failure in iron protein maturation leads to early senescence of the bacteroids.

Item Type:	Article
Uncontrolled Keywords:	medicago,iron,micronutrient,nitrogen fixation,nodulin-21,symbiosis,vacuole,physiology,plant science ,/dk/atira/pure/subjectarea/asjc/1300/1314
Faculty \ School:	Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Molecular Microbiology Faculty of Science > Research Groups > Plant Sciences
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	24 Jun 2020 00:02
Last Modified:	22 Oct 2022 06:21
URI:	https://ueaeprints.uea.ac.uk/id/eprint/75750
DOI:	10.1111/nph.16735

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