The Secrets of Hybrid Vigor

 

 

Hybrids fascinated Charles Darwin, supplying him with intriguing clues into the evolution of species. Now Weizmann Institute scientists are using hybrid organisms to investigate the genetic machinery of evolution.

 

Prof. Naama Barkai of the Molecular Genetics Department, Prof. Avraham Levy of the Plant Sciences Department, and research students Itay Tirosh and Sharon Reikhav focused on differences in gene expression between species.

 

In a study published in Science, the researchers found that hybrid yeast fit Darwin’s description of organisms that gain in crossbreeding – they grew faster than either parent yeast. One theory for hybrid vigor is based on the fact that two types of DNA sequences affecting gene expression can complement each other: sequences called “cis,” which are physically linked to the gene, and those called “trans,” located elsewhere in the genome. In certain crosses, a strong cis in a gene inherited from one parent might be combined with the strong trans of the gene inherited from the other parent, leading to extra gene expression. And that’s exactly what the researchers found: an especially high level of expression for certain genes.

 

The mechanisms for novel patterns of gene expression in hybrids may explain why they can be phenotypically different from either parent. Although hybrids are mostly sterile, several species do not rely solely on sexual reproduction, and genome hybridity is one way to rapidly gain new traits. Levy: “We are interested in applying the lessons from yeast to bread wheat, a species that contains different genomes merged into the same nucleus.”