Feeding the world’s human population in 2050, which is estimated to reach over 9 billion people, will require the agricultural industry to produce twice the amount of food it produces today. The environmental impact of agriculture is already huge: it is a major contributor to greenhouse gases emission, water and soil pollution and a threat to biodiversity. We cannot expand our fields into remaining forests and grasslands, but we need to produce all this extra food on the land that is already in use. Therefore, solutions for the future of agriculture need to include efficiency-improving technologies. Breeding new, more efficient crop varieties with our current technologies is time consuming and expensive. Because of this, the benefits of high-yielding seed varieties that are produced by large breeding companies are inaccessible to many small-scale farmers, especially in developing countries. Can we hack plant breeding and produce new crop varieties cheaper and faster? Let me explain how turning off sex in crop plants could help feed the world.
Sexual reproduction is all about mixing your genetic material with someone else’s. A sperm cell fertilizes an egg and the newly- formed offspring is a combination of the genetic material from both parents. Sex creates diversity, and this can be disadvantageous for agriculture. The reason why farmers need to buy seeds each year – if they want to produce the most from their land – is not because large breeding companies are greedy, but because crop plants reproduce sexually and only specific combinations of mother’s and father’s genes produce the best, high yielding plants. If farmers were to plant the harvested seeds next year, sex would have mixed up and redistributed all the genes, and produced a smaller harvest.
The idea to turn off sex in crop plants, as a way of “locking” certain genetic combinations and creating new varieties, has been around since 1930s. The approach taken in my research group to understand how such a “switch” from sexual to asexual reproduction could be engineered in crop plants is to use naturally- occurring asexual plants and figure out the hacks that evolution already has in place to transition from sexual to asexual reproduction. In nature, there are numerous examples of asexual plant and animal species. They don’t mix their genetic material with anyone. The females produce offspring from unfertilized eggs. Asexual reproduction transfers the exact genetic composition of the mother to all her offspring without mixing it up with the father’s genes.
Asexually produced offspring are expected to be identical. However, it is not known if asexual reproduction is necessarily followed by phenotypic uniformity (e.g. uniform seed size), even if all the offspring are genetically identical. In my research I use naturally-occurring asexual and sexual plants from genus Boechera as a model for studying factors affecting seed size variation, which is an agriculturally important trait. Boechera reproduce by pseudogamous apomixis, which means that “father’s” genes contribute to feeding the developing embryo that is a copy of the “mother”. In other words, contribution from pollen is required to produce the endosperm, which is the tissue in the seed providing nutrition for the developing embryo. Thus, while parents’ genes do not mix, there is paternal influence on offspring’s growth and survival through its effects on seed development. This paternal contribution is also a potential factor which contributes to the differences in seed size. I am using experimental genomic and transcriptomic approaches to study gene expression in developing seeds of sexual and asexual plants with the aim to identify candidate factors responsible for seed size variation.
This work is of general importance for understanding the evolution of sexual and asexual reproduction, and has a potential to enable technological advances for increasing crop yield via seed size increase.
About the Author
Dorota Paczesniak: I am interested in the evolutionary causes and consequences of different reproductive modes (sexuality, asexuality), and how the genetic variation in the natural populations is affected by the mode of reproduction. In my current postdoctoral project at IPK Gatersleben (Germany) I study seed size variation in asexual plants. My PhD at ETH Zurich (Switzerland) focused on the ecology and evolution of asexual snails from New Zealand. I also worked with sexual and asexual ostracods (small shrimp-like crustaceans) at the University of Sheffield (UK). I completed my Masters studies in biology at Jagiellonian University in Krakow (Poland), and my research project focused on genetic interactions.