The Nicotiana sylvestris nucleobase cation symporter 1 retains a dicot solute specificity profile

Nguyen, Jaclyn N.; Schein, Jessica R.; Hunt, Kevin A.; Tippmann-Feightner, J.A.; Rapp, Micah; Stoffer-Bittner, Amanda J.; Nalam, Vamsi J.; Funk, A.M.; Schultes, Neil P.; Mourad, George

doi:10.1016/j.plgene.2020.100226

Cited by 2 publications

(1 citation statement)

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“…A series of growth studies were performed in the presence of the toxic nucleobase analogue 8-azaguanine (8AG) that has been previously used to probe the solutebinding site capabilities of NCS2 and NCS1 guanine transporters (Mansfield et al 2009;Mourad et al 2012;Schein et al 2013;Rapp et al 2016;Funk et al 2020;Nguyen et al 2020). In a plate diffusion assay, JW4025-1 cells harbouring either pQE80L or pAS104 were imprinted onto separate halves of Petri plates and the centre of the plate treated with either control 1 mmol l À1 NaOH (solvent for dissolving 8AG) or 300 µg 8AG and grown overnight.…”

Section: Eaghxp Transports Guanine Hypoxanthine and 8azaguaninementioning

confidence: 99%

The guanine–hypoxanthine permease GhxP of Erwinia amylovora facilitates the influx of the toxic guanine derivative 6‐thioguanine

et al. 2020

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Aim Erwinia amylovora is the causal agent of fire blight, a devastating disease of apples and pears. This study determines whether the E. amylovora guanine–hypoxanthine transporter (EaGhxP) is required for virulence and if it can import the E. amylovora produced toxic analogue 6‐thioguanine (6TG) into cells. Methods and Results Characterization of EaGhxP in guanine transport deficient Escherichia coli reveals that it can transport guanine, hypoxanthine and the toxic analogues 8‐azaguanine (8AG) and 6TG. Similarly, EaGhxP transports 8AG and 6TG into E. amylovora cells. EaGhxP has a high affinity for 6TG with a Ki of 3·7 µmol l−1. An E. amylovora ⊿ghxP::Camr strain shows resistance to growth on 8AG and 6TG. Although EaGhxP is expressed during active disease propagation, it is not necessary for virulence as determined on immature apple and pear assays. Conclusions EaGhxP is not required for virulence, but it does import 6TG into E. amylovora cells. Significance and impact of the Study As part of the disease establishment process, E. amylovora synthesizes and exports a toxic guanine derivative 6TG. Our results are counter intuitive and show that EaGhxP, an influx transporter, can move 6TG into cells raising questions regarding the role of 6TG in disease establishment.

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