The team also found that gene pairs that are co-expressed in similar tissues are preferentially expressed from the same parent. Even in the rare cases when an Arabidopsis thaliana gene was more abundantly expressed in the hybrid, co-expressed genes would also be preferentially expressed from the Arabidopsis thaliana copy.
"Our findings suggest an additional network dependence, where genes fine-tuned to work together within either parental species prior to hybridization are more likely to be expressed together in the hybrid. This, in turn, ensures that these genes acquired from one parental species are kept together and are not lost in the genome over time," said Peter Chang, a graduate student at USC and lead author on the paper. "Plants have had a remarkable ability to adapt to different conditions throughout Earth's history, and we are just beginning to understand some of ways this is done."
Previous work has shown that plant genomes with historical duplications from tens of millions of years ago have lost one of the two copies in large blocks along the chromosome, consistent with the preferential loss of one parent's contribution.
Dilkes said the retained genes may have a role in the plants' fitness but genes that weren't expressed would be deleted from the genome.
"The genome is moving toward a two-copy organization, a diploid, by preferentially deleting one parent. When others have looked at genomes that have ancient duplications they see large blocks of duplications in which one block has a large number of genes and the other has a sparse gene content," Dilkes said. "Perhaps a cause of this pattern in the organization of genomes is preferential expression, and, all other things being equal, the gene that is more abundantly expressed will carry a greater proportion of the fitness load for any essential function."
|Contact: Brian Wallheimer|