A molecular genetic analysis of resistance to poleroviruses in sugar beet and oilseed rape

Gallagher, Eileen Wallace (2013) A molecular genetic analysis of resistance to poleroviruses in sugar beet and oilseed rape. Doctoral thesis, University of East Anglia.

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Abstract

Beet mild yellowing virus (BMYV) and Turnip yellows virus (TuYV) are both
poleroviruses that cause significant reduction in the yields of sugar beet and oilseed
rape respectively. Both viruses are transmitted by the aphid vector Myzus persicae.
Current control methods rely heavily on the use of insecticides for controlling the
aphids which can spread these viruses to a wide range of host plants. Recent EU
guidelines have tightened control on the use of some of these pesticides, meaning it
is becoming increasingly important to find alternative control methods. It is widely
agreed in the scientific community, that the best control method would be to generate
durable genetically resistant crop plants. In order to achieve this gene targets, either
for active or passive resistance, would need to be identified.
This study has built on a project that identified a naturally BMYV resistant A.
thaliana ecotype, Sna-1. Crosses of the susceptible ecotype (Col-0) to the resistant
ecotype Sna-1 identified the resistance as ‘passive’, where susceptibility was
dominant, and conditioned by a monogenic trait. This study began by characterising
the gene responsible for susceptibility by bulked segregant analysis and AFLP™.
This identified a region of ca. 5Mbp region on A. thaliana chromosome 4. This region
contains the Arabidopsis elongation initiation factor 4E (eIF4E) gene which has
already been implicated in susceptibility to other viruses. This gene has frequently
been shown to be important for viral infection in plants, and naturally occurring
mutations can result in resistance to other viruses. Further investigation revealed a
12 bp duplicated sequence in the Sna-1 eIF4E allele, located in a region that
encodes the cap-binding pocket of eIF4E. The same region has been shown to be
required for virus infection in other species. Infections were therefore carried out
using mutants in this gene, using TAS-ELISA. Previously susceptible Col-0 plants
containing a T-DNA insert, or EMS point mutations in the eIF4E gene were found to
be resistant to BMYV infection. Functional complementation with the Col-0 eIF4E
allele into a stock that contained Sna-1 eIF4E resulted in susceptibility to BMYV,
confirming its role as a susceptibility factor.
As BMYV and TuYV are closely related viruses it was hypothesised they
would share a similar infection strategy. The mutation in eIF4E was not enough to
prevent virus infection, and the method of infection of the UK-BB TuYV isolate
remains to be elucidated as infection studies in mutants with defective components of
the eukaryotic translation initiation factors, including eIF(Iso)4E gene, has so far
failed to identify any requirements for UK-BB TuYV infection. Several T-DNA insertion
lines in the eIF(iso)4E gene were tested but it was not possible to verify that any of
these lines were true knock-outs. However, the molelcular tools for future verification
have been developed. A recent report has implicated eIF(iso)4G components in
TuYV infection of Arabidopsis but this result could not be repeated in this study.
Further study is required to fully understand the mode of infection of both
viruses. It is expected that the identification of essential host genes required for virus
infection will aid in the breeding of genetically resistant crops, and reduce the current
dependence on harmful pesticides.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Mia Reeves
Date Deposited: 13 Mar 2014 10:39
Last Modified: 13 Mar 2014 10:39
URI: https://ueaeprints.uea.ac.uk/id/eprint/48150
DOI:

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