Gardening enthusiasts and scientists alike have long been captivated by hybrids, ranging from disease-resistant tomatoes to vibrant Stargazer lilies. These fascinating organisms found both in nature and agriculture, possess chromosomes derived from two or more parent species. In certain cases, such as strawberries and goldfish, the chromosomes from these diverse parents undergo a process called allopolyploidy, resulting in their duplication. Shedding light on this intricate genetic puzzle, a recent publication in Nature Communications introduces a new method to trace the ancestral origins of these polyploid hybrids.
Led by Adam Session, Assistant Professor of Biological Sciences at Binghamton University, and Daniel S. Rokhsar, Professor of Genetics, Evolution, and Development at the University of California, Berkeley, the research team unveils a novel approach that investigates genomic patterns within the hybrid itself. Unlike previous methods that relied on comparisons with non-hybrid species to decipher polyploid ancestry, this new technique enables the identification of distinct ancestral genomes by examining repetitive elements within the hybrid's chromosomes.
Session elaborated on the methodology, stating, "Each ancestral genome carries a unique set of repetitive elements. So, if we find sets of chromosomes in a polypoid that carry different repetitive elements, that proves hybrid ancestry and allows us to figure out which chromosomes were inherited together coming from the various progenitor species."
To demonstrate the effectiveness of their approach, the scientists applied it to well-studied polyploid hybrids, including tobacco, cotton, and cyprinid fish such as goldfish and carp. Additionally, they successfully resolved the disputed ancestries of other hybrids, such as false flax and strawberries.
"In many cases, the ancestors of living polyploids are not known. Using our method, we can figure out the ancestral origin of different chromosomes just by studying the polyploid genome itself, and divide the chromosomes into sets, or ‘sub-genomes,’ derived from its various ancestor," Session explained. “In addition to identifying the subgenomes, we can also tell you the order in which they were put together.”
The process of polyploidization, which involves genome duplication in a hybrid, is more prevalent in plants compared to animals. This is due to plants' greater tolerance for multiple copies of their genomes. Although polyploidization does occur in select fish and amphibian species, it is relatively more complex in animals. As a breakthrough finding, the researchers establish that goldfish share the same duplicated gene sequences as common carp, indicating a common hybrid ancestor.
While polyploidy remains absent in mammals, hybridization can still transpire. A notable example is the mule, a hybrid of horses and donkeys. Male mules are typically sterile, although female mules can successfully mate with either parent species. However, without genomic duplication, the distinct hybrid type cannot be stably perpetuated.
For instance, cotton, a tetraploid species, possesses four copies of each chromosome, two from each of its two ancestors. Alternatively, hexaploids like false flax harbor six chromosomes derived from three parent species. Strawberry, an octoploid, ultimately boasts eight copies of each chromosome, contributed by four ancestral species.
Polyploid organisms exhibit complex biology that scientists are still unraveling. The sub-genome structure of their genomes represents a significant step forward in understanding their intricate genetic makeup. Over millions of years, the genes contributed by each parental species evolve within the context of the new polyploid organism. Some redundant genes become obsolete or deactivated, while others may develop new functions or establish novel interactions with their counterparts in other sub-genomes. The researchers argue that the order in which parental species are incorporated into a higher polyploid, like the strawberry, can profoundly influence these evolutionary processes. Deciphering the impact of duplicated genes on the evolving polyploid remains an ongoing challenge, according to the authors.
Session emphasized the importance of comprehending polyploid genome evolution, stating, “Understanding polyploid genome evolution as a whole is important to the wider field of plant biology. Many important crops like maize and emerging biofuel crops like miscanthus and switchgrass are affected by this process, and we hope to take advantage of their genomic flexibility to breed new and improved varieties.”
This research provides an innovative approach to deciphering the ancestral origins of polyploid hybrids. By analyzing the genomic patterns within these fascinating organisms, scientists can determine the intricate evolutionary processes that shape their genetic makeup. The study's findings have far-reaching implications for the field of plant biology, offering opportunities to develop enhanced crop varieties that can withstand various challenges and contribute to sustainable agriculture.
Led by Adam Session, Assistant Professor of Biological Sciences at Binghamton University, and Daniel S. Rokhsar, Professor of Genetics, Evolution, and Development at the University of California, Berkeley, the research team unveils a novel approach that investigates genomic patterns within the hybrid itself. Unlike previous methods that relied on comparisons with non-hybrid species to decipher polyploid ancestry, this new technique enables the identification of distinct ancestral genomes by examining repetitive elements within the hybrid's chromosomes.
Session elaborated on the methodology, stating, "Each ancestral genome carries a unique set of repetitive elements. So, if we find sets of chromosomes in a polypoid that carry different repetitive elements, that proves hybrid ancestry and allows us to figure out which chromosomes were inherited together coming from the various progenitor species."
To demonstrate the effectiveness of their approach, the scientists applied it to well-studied polyploid hybrids, including tobacco, cotton, and cyprinid fish such as goldfish and carp. Additionally, they successfully resolved the disputed ancestries of other hybrids, such as false flax and strawberries.
"In many cases, the ancestors of living polyploids are not known. Using our method, we can figure out the ancestral origin of different chromosomes just by studying the polyploid genome itself, and divide the chromosomes into sets, or ‘sub-genomes,’ derived from its various ancestor," Session explained. “In addition to identifying the subgenomes, we can also tell you the order in which they were put together.”
The process of polyploidization, which involves genome duplication in a hybrid, is more prevalent in plants compared to animals. This is due to plants' greater tolerance for multiple copies of their genomes. Although polyploidization does occur in select fish and amphibian species, it is relatively more complex in animals. As a breakthrough finding, the researchers establish that goldfish share the same duplicated gene sequences as common carp, indicating a common hybrid ancestor.
While polyploidy remains absent in mammals, hybridization can still transpire. A notable example is the mule, a hybrid of horses and donkeys. Male mules are typically sterile, although female mules can successfully mate with either parent species. However, without genomic duplication, the distinct hybrid type cannot be stably perpetuated.
For instance, cotton, a tetraploid species, possesses four copies of each chromosome, two from each of its two ancestors. Alternatively, hexaploids like false flax harbor six chromosomes derived from three parent species. Strawberry, an octoploid, ultimately boasts eight copies of each chromosome, contributed by four ancestral species.
Polyploid organisms exhibit complex biology that scientists are still unraveling. The sub-genome structure of their genomes represents a significant step forward in understanding their intricate genetic makeup. Over millions of years, the genes contributed by each parental species evolve within the context of the new polyploid organism. Some redundant genes become obsolete or deactivated, while others may develop new functions or establish novel interactions with their counterparts in other sub-genomes. The researchers argue that the order in which parental species are incorporated into a higher polyploid, like the strawberry, can profoundly influence these evolutionary processes. Deciphering the impact of duplicated genes on the evolving polyploid remains an ongoing challenge, according to the authors.
Session emphasized the importance of comprehending polyploid genome evolution, stating, “Understanding polyploid genome evolution as a whole is important to the wider field of plant biology. Many important crops like maize and emerging biofuel crops like miscanthus and switchgrass are affected by this process, and we hope to take advantage of their genomic flexibility to breed new and improved varieties.”
This research provides an innovative approach to deciphering the ancestral origins of polyploid hybrids. By analyzing the genomic patterns within these fascinating organisms, scientists can determine the intricate evolutionary processes that shape their genetic makeup. The study's findings have far-reaching implications for the field of plant biology, offering opportunities to develop enhanced crop varieties that can withstand various challenges and contribute to sustainable agriculture.