Mating system shifts and transposable element evolution in the plant genus Capsella

Area of Science:

• Genomics
• Evolutionary Biology
• Plant Science

Background:

• Transposable elements (TEs) are significant components of eukaryotic genomes, particularly in plants.
• Variation in TE abundance across plant taxa is substantial, but the evolutionary forces driving it are not fully understood.
• Mating systems are theorized to influence the evolutionary dynamics of TEs.

Purpose of the Study:

• To investigate the abundance, genomic distribution, and population frequencies of TEs in three closely related *Capsella* species with differing mating systems.
• To understand how mating system evolution affects TE dynamics in plants.

Main Methods:

• Utilized the *Capsella rubella* reference genome.
• Performed short-read whole-genome sequencing on multiple individuals from three species: *C. rubella* (self-compatible), *C. orientalis* (self-compatible), and *C. grandiflora* (self-incompatible).
• Quantified TE abundance, genome distributions, and population frequencies.

Main Results:

• Observed distinct TE evolution dynamics in the two self-compatible species: *C. rubella* showed a slight increase in TE copy number, while *C. orientalis* exhibited a significant decrease compared to *C. grandiflora*.
• TE copy number changes were genome-wide and consistent across different TE classes.
• Highest TE abundances near genes were found in the self-incompatible species, *C. grandiflora*.
• Differences in TE population frequency distributions were identified among the three species.

Conclusions:

• The evolution of selfing appears to have differential impacts on TE evolution over short and long evolutionary timescales.
• Cross-species comparisons of TE abundance are susceptible to reference genome bias, highlighting the importance of controlling for this bias.