Events of gene fusion have been reported in several organisms. However, the general role of gene fusion as part of new gene origination remains unknown.
Evolutionary new gene, fused from more than 2 parental genes, could duck out the detrimental step of tardy point mutation evolution, and have been shown to be critical in the understanding of phenotypic evolution.
The research team said: “we cannot distinguish gene fusion events from gene fission events without out-group support, therefor we designed and created new pipelines to dynamically detect fusion genes across phylogeny and conducted genome-wide interrogations of four Oryza genomes (Figure 1).
As a result, the research group lead by Prof. ZHANG Chengjun of Kunming Institute of Botany, Chinese Academy of Sciences (KIB/CAS) detect 310 fusion genes across four young diploid genome Oryza species.
The estimated rate of origination of fusion genes in the Oryza genus is as high as 63 fusion genes per species per million years by average, and fixed at 16 fusion genes per species per million years by SNP calling in genomic population.
Both of the speeds are much higher than that in flies. The team find more than 44% of the fusion genes are expressed and 90% of gene pairs show strong signals of purifying selection, suggesting potential bio-function of these expressed fusion genes.
Based on the expressional correlation between fusion gene and parental genes in different tissues, we got both sub-functionalized and neo-functionalized fusion gene.
Furthermore, CRISPR/Cas9 knockout lines indicates that two newly formed fusion genes regulate phenotype traits including seed germination (Figure 2), shoot length and root length, and both of them are best responsive to drought stress, suggesting the adaptative functional significance of these genes in phenotypic evolution.
Conclusively, our study created a creative approach to understanding of new genes, providing a method and theory basis in the new era of big data.
The results of the study were published in the Genome Biology under the title of “Gene fusion as an important mechanism to generate new genes in the genus Oryza”.

 
Figure 1 Pipelines to dynamically detect fusion genes across phylogeny. (Image by KIB)
 
Figure 2 CRISPR/Cas9 knockout lines indicate that two newly formed fusion genes regulate phenotype traits.  (Image by KIB)

           (Editor: YANG Mei)