Genome Origin and Evolution of an Important Crop, Camelina sativa, and its Relatives Uncovered by Czech Scientists

29. Nov. 2019

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Terezie Mandakova and her colleagues Milan Pouch and Martin Lysak from Martin Lysak Research Group from the Central European Institute of Technology, Masaryk University, deciphered the ancestors and closest relatives of Camelina sativa plant in such depth like no other scientist before. The previous genome sequencing-based study showed that the camelina genome consists of three subgenomes merged through hybridization between unknown parental species. Terezie Mandakova and her colleagues aimed to identify the most probable parental genomes of the hexaploid camelina, and moreover to reconstruct genome structure and evolution of all known Camelina species. New pieces of camelina genome history provide now fresh insights needed to explore possibilities for future improvement of this ancient and economically important crop. The unique study of Mandakova and colleagues was published in the November 2019 issue of the prestigious journal The Plant Cell (IF 8.6) and also highlighted in the journals In Brief section. 

Health Benefits and Economic Importance of Camelina

Most plant scientists conduct their experiments on a model plant Arabidopsis thaliana from the mustard family. Mandakova and Lysak decided to study genome evolution of Camelina sativa (also known as false flax or gold of pleasure) – a close and commercially important relative of Arabidopsis. Camelina sativa is an ancient oilseed crop which has been grown in Europe as early as 4 000 BC. Camelina was largely forgotten as a crop, but was recently re-discovered for its unique characteristics. Camelina oil, extracted from seeds, has a very high content of omega-3 fatty acids (39%). Most of the fats in camelina oil are polyunsaturated. These “good fats” are essential for healthy cell function in your body, for example by reducing the risk of heart diseases. Camelina oil is also excellent for skin and hair due to ample amounts of vitamin E and omega fatty acids. Last but not least it is known for its antioxidant and anti-inflammatory properties which makes it perfect for aiding out our immune system. Camelina oil can be used as cooking oil, pure oil, food supplement or biofuel, and it is increasingly popular for its potential as a renewable industrial feedstock. Camelina is also known for its very good drought resistance and can be grown almost everywhere, which makes this plant even more valuable, considering the climate change. Research has also been done to develop its oil for jet fuel and other high-value chemicals. Presently, camelina is grown mainly in the United States, Canada, Slovenia, Ukraine, China, Finland, Germany and Austria.

Comparative Chromosome Painting as a Tool for Plant Genome Analysis

Canadian researches performed sequencing of the genome of Camelina sativa already in 2014 and found out that its genome is hexaploid and consists of three distinct subgenomes – a similar genome make-up to oilseed rape and wheat. Mandakova and Lysak expanded the current knowledge about camelina much further with the help of a special method called comparative chromosome painting. While this method is commonly used in human and animal research, only few plant scientists around the world use it for studying plant genomes. But how does chromosome painting work? The foundation is the similarity between Arabidopsis and other plants from the mustard family. Arabidopsis genome is cut into tiny fragments with the help of restriction enzymes, the fragments are cloned into bacterial plasmids in order to create so called BACs – bacterial artificial choromosomes. Those BAC “cocktails” are than being labeled with fluorescent dyes and hybridized on chromosomes of the studied species from the mustard family. This allows that scientists can reconstruct the genome structure of a species, identify chromosome rearrangements, parental genomes, and compare the genome structure of various plant species.

Thanks to combination of several cytogenetic methods such as comparative chromosome painting, genomic in situ hybridization (a method that allows the identification of parental genomes within the genome of putative hybrid) and multi-gene phylogenetic analyses, Mandakova and her colleagues revealed the entire genome structure of the known diploid, tetraploid and hexaploid Camelina species, including false flax. Genomes of diploid Camelina species (C. hispida, n = 7 chromosomes; C. laxa, n = 6; and C. neglecta, n = 6) originated from an ancestral n = 7 genome. The allotetraploid C. rumelica genome (n = 13, N6H genome) arose from hybridization between diploids C. neglecta (n = 6, N6) and C. hispida (n = 7, H). The allohexaploid genomes of C. sativa (n = 20, N6N7H) originated through hybridization between an auto-allotetraploid C. neglecta-like genome (n = 13, N6N7) and C. hispida (n = 7, H), and the three subgenomes remained overall stable since the genome merger.

The used cytogenetic methods are extremely precise and cytogenetic maps developed by Martin Lysak´s group are used by other well-known institutes as a basis for genome formation or specification of genetic structures. Mandakova managed to reconstruct the parental genomes of Camelina sativa and to discover the evolutionary history of the hexaploid genome and the mechanisms responsible for the current form of studied genomes. She successfully traced the camelina genome up millions of years into the past and witnessed all naturally occurring genetic crossings of this unique plant, that took place without human intervention. No other scientist revealed camelina´s genome in such depth like Terezie Mandakova and her colleagues.

Remarkably, the ancestral and diploid Camelina genomes were shaped by complex chromosomal rearrangements – so called chromothripsis. Chromothripsis can be explained as catastrophic event in cell´s history that causes clustering of up to thousand cells in one location. This event is commonly associated with human disorders and leads to development of genome-specific shattered chromosomes. Chromothripsis is very rare in plants but very common in disorders such as leukemia.

This unique discovery was possible thanks to standard three-year GACR grant titled Missing Links: Genome Evolution in Camelina Species (GA17-13029S), that was awarded to Terezie Mandakova by Czech Science Foundation GACR.

Further Research and Expected Impact

There are multiple implications for the groundbreaking discovery of Mandakova and Lysak. Breeders like to improve the seed yield, oil content and other agronomic traits of the camelina crop. This can be done by producing new camelina lines by crossing the now identified parental Camelina species. Furthermore, the diploid and tetraploid Camelina genomes should be more amenable to genome sequencing and uncovering the key genes influencing yield and other desired agronomic traits.

To read the full article please click HERE. To access the In Brief article please click HERE.

About the Author

Terezie Mandakova is regarded as a world-class scientist in plant cytogenetics and one of the most successful female researchers at CEITEC. As a member of Martin Lysak’s research group, she is engaged in the study of the evolution of the plant genome structure of Brassicaceae and its relatives. Her engagement, enthusiasm and time management are virtually enviable and contagious to her students and collaborators. Thanks to these exceptional qualities Terezie achieved several remarkable accomplishments in the field of plant genome research. In 2018 Terezie was awarded for extraordinary research results achieved by scientists in the age group under 35 from the Rector of Masaryk University. Thanks to her excellent scientific results, Terezie is regarded as one of the best plant cytogenetics scientists worldwide, with more than 70 publications and 1800 citations and an h-index of 21.

Already during her PhD study and early years of her career, Mandakova published several highly cited papers making a very significant contribution to our understanding of chromosomal and genome evolution in plants. She published in numerous top-ranking journals either with her home Lysak lab or international collaborators (e.g., Nature Genetics, eLIFE, Plant Cell, New Phytologist, Plant Journal, Plant Physiology, Curr Opin Plant Biol, BMC Evolutionary Biology, etc.). She has become a respected member of the scientific community, frequently being selected as an invited speaker at international conferences.

Mandakova is also contributing to the society through her pedagogical activities. She is recognized as a beloved supervisor, teacher and trainer, and a wonderful colleague keeping up the good spirit in the lab. Terezie is an inspiration for her students and colleagues, not only because of her extraordinary scientific results but also due to her enthusiasm for science, and hardworking approach combined with kindness and modesty.

 

Author: Ester Jarour

 



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