A Virus-Derived Stacked RNAi Construct Confers Robust Resistance to Cassava Brown Streak Disease
Loading...
Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Plant Science
Abstract
Cassava brown streak disease (CBSD) threatens food and economic security for
smallholder farmers throughout East and Central Africa, and poses a threat to cassava
production in West Africa. CBSD is caused by two whitefly-transmitted virus species:
Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV)
(Genus: Ipomovirus, Family Potyviridae). Although varying levels of tolerance have been
achieved through conventional breeding, to date, effective resistance to CBSD within
East African cassava germplasm has not been identified. RNAi technology was utilized
to integrate CBSD resistance into the Ugandan farmer-preferred cassava cultivar TME
204. Transgenic plant lines were generated expressing an inverted repeat construct
(p5001) derived from coat-protein (CP) sequences of CBSV and UCBSV fused in
tandem. Northern blots using probes specific for each CP sequence were performed to
characterize 169 independent transgenic lines for accumulation of CP-derived siRNAs.
Transgenic plant lines accumulating low, medium and high levels of siRNAs were bud
graft challenged with the virulent CBSV Naliendele isolate alone or in combination with
UCBSV. Resistance to CBSD in the greenhouse directly correlated to levels of CPderived
siRNAs as determined by visual assessment of leaf and storage root symptoms,
and RT-PCR diagnosis for presence of the pathogens. Low expressing lines were found
to be susceptible to CBSV and UCBSV, while medium to high accumulating plant
lines were resistant to both virus species. Absence of detectable virus in the best
performing p5001 transgenic lines was further confirmed by back-inoculation via sap
or graft challenge to CBSD susceptible Nicotiana benthamiana and cassava cultivar
60444, respectively. Data presented shows robust resistance of transgenic p5001 TME
204 lines to both CBSV and UCBSV under greenhouse conditions. Levels of resistance
correlated directly with levels of transgene derived siRNA expression such that the latter
can be used as predictor of resistance to CBSD
Description
Keywords
Cassava brown streak disease (CBSD), Resistance to CBSD, RNAi, TME 204, Transgenic, siRNA, CBSV, UCBSV
Citation
Beyene G, Chauhan RD, Ilyas M, Wagaba H, Fauquet CM, Miano D, Alicai T and Taylor NJ (2017) A Virus-Derived Stacked RNAi Construct Confers Robust Resistance to Cassava Brown Streak Disease. Front. Plant Sci. 7:2052. doi: 10.3389/fpls.2016.02052