RNAi-mediated resistance to diverse isolates belonging to two virus species involved in Cassava brown streak disease
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Date
2011
Journal Title
Journal ISSN
Volume Title
Publisher
Molecular plant pathology
Abstract
Cassava brown streak disease (CBSD) is emerging as one of the
most important viral diseases of cassava (Manihot esculenta) and
is considered today as the biggest threat to cassava cultivation in
East Africa. The disease is caused by isolates of at least two
phylogenetically distinct species of single-stranded RNA viruses
belonging to the family Potyviridae, genus Ipomovirus. The two
species are present predominantly in the coastal lowland
[Cassava brown streak virus (CBSV); Tanzania and Mozambique]
and highland [Cassava brown streak Uganda virus (CBSUV); Lake
Victoria Basin, Uganda, Kenya and Malawi] in East Africa. In this
study, we demonstrate that CBSD can be efficiently controlled
using RNA interference (RNAi). Three RNAi constructs targeting
the highland species were generated, consisting of the full-length
(FL; 894 nucleotides), 397-nucleotide N-terminal and 491-
nucleotide C-terminal portions of the coat protein (CP) gene of a
Ugandan isolate of CBSUV (CBSUV-[UG:Nam:04]), and expressed
constitutively in Nicotiana benthamiana. After challenge with
CBSUV-[UG:Nam:04], plants homozygous for FL-CP showed the
highest resistance, followed by the N-terminal and C-terminal
lines with similar resistance. In the case of FL, approximately 85%
of the transgenic plant lines produced were completely resistant.
Some transgenic lines were also challenged with six distinct
isolates representing both species: CBSV and CBSUV. In addition
to nearly complete resistance to the homologous virus, two FL
plant lines showed 100% resistance and two C-terminal lines
expressed 50–100% resistance, whereas the N-terminal lines
succumbed to the nonhomologous CBSV isolates. Northern blotting
revealed a positive correlation between the level of
transgene-specific small interfering RNAs detected in transgenic
plants and the level of virus resistance.This is the first demonstration
of RNAi-mediated resistance to CBSD and protection across
very distant isolates (more than 25% in nucleotide sequence)
belonging to two different species: Cassava brown streak virus
and Cassava brown streak Uganda virus
Description
Keywords
RNAi-mediated resistance, Virus species, Cassava brown streak disease
Citation
Patil, B. L., Ogwok, E., Wagaba, H., Mohammed, I. U., Yadav, J. S., Bagewadi, B., ... & Fauquet, C. M. (2011). RNAi‐mediated resistance to diverse isolates belonging to two virus species involved in Cassava brown streak disease. Molecular plant pathology, 12(1), 31-41. DOI: 10.1111/J.1364-3703.2010.00650.X