Tomlinson, Katie R., Pablo-Rodriguez, José Luis, Bunawan, Hamidun, Nanyit, Sarah, Green, Patrick, Miller, Josie, Seal, Susan E. ORCID: https://orcid.org/0000-0002-3952-1562, Bailey, Andy M. and Foster, Gary D. (2019) Cassava brown streak virus Ham1 protein hydrolyses mutagenic nucleotides and is a necrosis determinant. Molecular Plant Pathology, 20 (8). pp. 1080-1092. ISSN 1464-6722 (Print), 1364-3703 (Online) (doi:10.1111/mpp.12813)

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Abstract

Cassava brown streak disease (CBSD) is a leading cause of cassava losses in East and Central Africa and is currently having a severe impact on food security. The disease is caused by two viruses within the Potyviridae family: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), which both encode atypical Ham1 proteins with highly conserved ITP pyrophosphohydrolase (ITPase) domains. ITPase proteins are widely encoded by plant, animal and archaea. They selectively hydrolyse mutagenic nucleotide triphosphates (NTP) to prevent their incorporation into nucleic acid and thereby function to reduce mutation rates. It has previously been hypothesised that U/CBSVs encode Ham1 proteins with ITPase activity to reduce viral mutation rates during infection. In this study, we investigate the potential roles of U/CBSV Ham1 proteins. We show that both CBSV and UCBSV Ham1 proteins have ITPase activities through in vitro enzyme assays. Deep-sequencing experiments found no evidence of the U/CBSV Ham1 proteins providing mutagenic protection during infections of Nicotiana hosts. Manipulations of the CBSV Tanza infectious clone were performed, including a Ham1 deletion, ITPase point mutations and UCBSV Ham1 chimera. Unlike severely necrotic wild-type CBSV Tanza infections, infections of Nicotiana benthamiana with the manipulated CBSV ICs do not develop necrosis, indicating that that the CBSV Ham1 is a necrosis determinant. We propose that the presence of U/CBSV Ham1 proteins with highly conserved ITPase motifs indicates that they serve highly selectable functions during infections of cassava and may represent a Euphorbia host adaptation that could be targeted in anti-viral strategies.

Item Type:	Article
Additional Information:	© 2019 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Uncontrolled Keywords:	Virus, Cassava, Cassava brown streak virus, Ugandan cassava brown streak virus, Cassava brown streak disease, Food security
Subjects:	S Agriculture > S Agriculture (General)
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > Natural Resources Institute Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department
Last Modified:	01 May 2020 12:19
URI:	http://gala.gre.ac.uk/id/eprint/23737

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