Horizontal Gene Transfer has Impacted cox1 Gene Evolution in Cassytha filiformis

Area of Science:

• Evolutionary Biology
• Molecular Evolution
• Plant Genetics

Background:

• The mitochondrial gene cox1 is frequently implicated in horizontal gene transfer (HGT) among angiosperms.
• Understanding the diversity of cox1 copies within species and novel intron acquisition mechanisms remains limited.

Purpose of the Study:

• To investigate the variation and evolution of the cox1 gene in Cassytha filiformis, a parasitic plant.
• To explore the existence of different cox1 copies and novel intron acquisition pathways.

Main Methods:

• Identification and characterization of cox1 gene copies in C. filiformis samples.
• Bioinformatic analyses including INDEL characterization and phylogenetic analyses.
• Comparative analysis of cox1 intron content (CCT).

Main Results:

• Discovery of two stable, inheritable cox1 gene copies (Type I and Type II) with distinct base compositions and indel profiles within C. filiformis.
• Type I cox1 exhibits intact open reading frames, while Type II is a pseudogene with premature stop codons.
• Phylogenetic and CCT analyses support dual origins: Type I likely vertically inherited with intron capture, and Type II integrally transferred from Convolvulaceae species.

Conclusions:

• Cassytha filiformis harbors two independently acquired cox1 gene copies, demonstrating two distinct horizontal gene transfer events.
• This study enhances understanding of cox1 evolution in parasitic plants and highlights novel HGT mechanisms beyond intron homing.
• The findings raise further questions regarding the evolutionary dynamics of mitochondrial genes in angiosperms.