GM plants in the pipeline – what has already been tried

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 modified 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”. 

http://www.landesbioscience.com/journals/gmcrops/IlardiGMC2-1.pdf

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.

http://www.agroscope.admin.ch/index_phytosanitaire/02224/02239/02241/index.html?lang=de

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.