1.
Which paper did you choose as your first step? Why did
you choose this paper? Please give a short summary (2-3 sentences) of this
paper.
I first thought about subjects other than
drought which we defined as the major challenges for the Swiss agriculture. I decided
that I wanted to know more about resistances which scientists had already tried
to achieve in plants. I therefore thought to address the challenge of new pests
arriving in Switzerland.
I found the very general and long article “Engineering
Pathogen Resistance in Crop Plants: Current Trends and Future Prospects” (accessible
when connected to the ZHAW) http://www.annualreviews.org/doi/pdf/10.1146/annurev-phyto-073009-114430
The article explains the huge potential of
different genetically modified plants with new resistances against fungal
diseases, bacteria and viruses. It also explores the reasons, why so few new
crops have been introduced to the global market. It gives an overview (the
charts) of the plants that have been produced with resistances so far and then
highlights some of the more recent promising strategies.
I limited myself to the introduction and
summary points and decided to mainly focus on virus resistances. There are
several viruses also causing damage in Switzerland. What is more, biocontrol is
not possible with viruses and in contrast to bacterial of fungal diseases there
are also no other possibilities to free the crops from them. This is why I
found it particularly interesting to focus on virus resistant GM plants.
2.
What kinds of plants have been genetically modified
addressing your chosen future challenge in Swiss agriculture?
Many plants have already been genetically
modified in order to be resistant to viruses. Here a few examples:
-
Squash: resistant to the Cucumber mosaic virus, Watermelon
mosaic virus 2 and Zucchini Yellow
mosaic virus
-
Papaya: resistant to Papaya Ringspot-Virus
-
Melon: resistant to Papaya Ringspot-Virus and Zucchini
Yellow mosaic virus
-
Wheat and other cereals: resistant to e.g. Barley Yellow dwarf virus
-
Tomato: resistant to the Tomato yellow leaf curl virus
-
Tobacco: resistant to the Tobacco mosaic virus
-
Potato: resistant to the Potato leaf roll virus or Potato
spindle tuber viroid and many more
-
Chrysanthemum: resistant to the Chrysanthemum stunt viroid
-
Plum: resistant to the Plum pox potyvirus (PPV)
Most of those plants, except for tobacco, melon
and papaya, are grown in Switzerland and therefore the efforts of genetic
engineering to make these plants resistant to detrimental viruses could be
relevant for us, too. I will focus on the Plum
pox potyvirus later.
3.
Which genes were used?
All viral molecules, including genomes,
represent potential targets for a genetically modiļ¬ed resistance strategy,
since these molecules are not separated from the plant cell by any physical
barrier. Viral coat protein (CP) genes and viral non-structural protein genes,
as well as antisense DNA and DNA for viral satellite RNA, have all been used to
produce virus-resistant plants, but CP’s are most commonly used.
Almost all viruses express proteins of the
following three types: coat proteins (CPs), movement proteins, and proteins
involved in genome replication. Natural defence mechanisms in plants are known
to target these proteins as well as the viral genomes.
The strategy is the pathogen mimicry or
pathogen-derived resistance (PDR), where the plant is designed to express
important, recognizable features of the pathogen.
4.
Which of the transgenic plants you studied do you find
most useful? What other solutions could you think of to achieve the same
effect?
I especially studied the paper “Genetically
engineered resistance to Plum pox virus
infection in herbaceous and stone fruit hosts”.
The Plum
pox virus infects plum, apricot, peach and also wild Prunus species and is
the causal agent of Sharka, the most detrimental viral disease affecting stone
fruit trees.
I know that the Plum pox virus is again a problem in Switzerland at the moment and
that all the measures are taken in order to eradicate this virus. It is a
quarantine organism which means that strict controlling is compulsory and the
contaminated trees have to be reported and destroyed. These measures are the
present solution to the problem. GM trees would offer an alternative in the
future.
But there are also naturally tolerant species and it might also be an option to try and make trees Sharka tolerant with conventional breeding methods, though this is often difficult for trees and takes longer.
