Transposon-linked plasticity may contribute to drought tolerance in a pantropical invader, Mikania micrantha.

BACKGROUND AND AIMS: Plant invasion poses severe threats to biodiversity, ecosystem stability, and human society. The prevailing "small-genome advantage" hypothesis-which attributes invasiveness to compact genomes that allow fast growth, high seed output, and short generation times-cannot explain why some aggressive invaders carry relatively large genomes. Here, we seek to explore why some large-genome plants are highly invasive.

METHODS

Using the pantropical, large-genome invader Mikania micrantha as a model, we integrate controlled experiments, whole-genome resequencing, and transcriptomics to show that long-terminal-repeat retrotransposons (LTR-RTs)-the dominant repeats comprising 54.22% of its genome-may confer an advantage during rapid range expansion.

KEY

RESULTS

Populations with larger genomes tended to exhibit stronger drought responsive activation of specific Ty1-copia and Ty3-gypsy retrotransposons. These elements may contribute to phenylpropanoid pathway activation, which indicates a potentially adaptive role of phenylpropanoids in drought response.

CONCLUSIONS

Genomic abundance is associated with environmental responsiveness, and LTR-RTs may function as eco-evolutionary catalysts that could allow large-genome plants to expand their ranges and become formidable invaders. Our findings uncover a previously overlooked benefit of large genomes and highlight transposon-driven plasticity as a candidate driver of invasion success worthy of further investigation.