Which factors contribute most to genome size variation within angiosperms?

Abstract

Genome size varies greatly across the flowering plants and has played an important role in shaping their evolution. It has been reported that many factors correlate with the variation in genome size, but few studies have systematically explored this at the genomic level. Here, we scan genomic information for 74 species from 74 families in 38 orders covering the major groups of angiosperms (the taxonomic information was acquired from the latest Angiosperm Phylogeny Group (APG IV) system) to evaluate the correlation between genome size variation and different genome characteristics: polyploidization, different types of repeat sequence content, and the dynamics of long terminal repeat retrotransposons (LTRs). Surprisingly, we found that polyploidization shows no significant correlation with genome size, while LTR content demonstrates a significantly positive correlation. This may be due to genome instability after polyploidization, and since LTRs occupy most of the genome content, it may directly result in most of the genome variation. We found that the LTR insertion time is significantly negatively correlated with genome size, which may reflect the competition between insertion and deletion of LTRs in each genome, and that the old insertions are usually easy to recognize and eliminate. We also noticed that most of the LTR burst occurred within the last 3 million years, a timeframe consistent with the violent climate fluctuations in the Pleistocene. Our findings enhance our understanding of genome size evolution within angiosperms, and our methods offer immediate implications for corresponding research in other datasets.

Abstract

Genome size is a biodiversity trait that shows staggering diversity across the flowering plants, which plays an important role in shaping the evolution of plants. Here, we scan the genomic information of 54 species from 52 families covering the major groups of angiosperms and evaluate the correlation between variations of genome sizes and different genome characters. We surprisingly find only LTRs significantly positively correlate with genome size variation, while polyploidization does not, and genome size acts as an evolutionary character that helps each species adapt to different environments with different patterns (different types of TEs burst or polyploidization).