Molecular bases for the stronger plastic response to high nitrate in the invasive plant Xanthium strumarium compared with its native congener.

High expressions of nitrate use and photosynthesis-related transcripts contribute to the stronger plasticity to high nitrate for the invader relative to its native congener, which may be driven by hormones. Strong phenotypic plasticity is often considered as one of the main mechanisms underlying exotic plant invasions. However, few studies have been conducted to investigate the related molecular mechanisms. Here, we determined the differences in the plastic responses to high nitrate between the invasive plant X. strumarium and its native congener, and the molecular bases by transcriptome analysis and quantitative real-time PCR validation. Our results showed that the invader had higher plasticity of growth, nitrogen accumulation and photosynthesis in responses to high nitrate than its native congener. Compared with its congener, more N utilization-related transcripts, including nitrate transporter 1/peptide transporter family 6.2 and nitrate reductase 1, were induced by high nitrate in the root of X. strumarium, improving its N utilization ability. More transcripts coding for photosynthetic antenna proteins were also induced by high nitrate in the shoot of X. strumarium, enhancing its photosynthesis. Hormones may be involved in the regulation of the plastic responses to high nitrate in the two species. Our study contributes to understanding the molecular mechanisms underlying the stronger plasticity of the invader in responses to high nitrate, and the potential function of plant hormones in these processes, providing bases for precise control of invasive plants using modern molecular techniques.