Responses to low phosphorus conditions of Triadic sebifera (Euphorbiaceae), an invasive plant species on Miyajima Island, southwest Japan

Abstract

ABSTRACT Phosphorus (P) is a crucial nutrient for plant growth, but its availability in soils is often limited. Invasive plants have shown enhanced utilization of essential elements in soil, including P, compared to native plants, contributing to their success. This study investigated the responses of Triadic sebifera, an invasive species, to low P conditions. We compared T. sebifera with native Mallotus japonicus and other local plants in field conditions and further examined T. sebifera‘s response to low P availability using hydroponic systems and RNA-seq analysis. The hydroponic experiments involved three treatment groups with different P concentrations (0, 6.4, and 64 µM ). Field survey results revealed that T. sebifera exhibited higher P use efficiency and more efficient P resorption compared to other native plants on Miyajima Island. However, no significant differences in P concentrations were found between T. sebifera and native plant M. japonicus, another member of the Euphorbiaceae family. This suggests that the efficient use and resorption of P may not be unique to the invasive species T. sebifera, but rather a trait shared by members of the Euphorbiaceae family. Hydroponic experiments further demonstrated the response of T. sebifera to low P availability. Under 0 µM P treatment, T. sebifera showed enhanced secretion of acid phosphatase (AcPase). At 6.4 µM P treatment, the plant maintained growth, exhibited potential enhancement in root development, high chlorophyll content, and high root biomass, and demonstrated relatively high AcPase secretion, but displayed a P-deficient state compared to the 0 and 64 µM P treatments. RNA-seq analysis provided insights into the potential strategies of T. sebifera in low P environments. It revealed that T. sebifera under 0 µM P treatment exhibits upregulation of transcripts related to P acquisition, antioxidant activities, stress responses, and arsenate uptake risk or regulation. Additionally, T. sebifera showed upregulation of transcripts associated with secondary metabolism under 6.4 µM P treatment, suggesting mechanisms for more efficient P acquisition and environmental stress defense. This study highlights the strategies of T. sebifera under low P availability, suggesting a role in enhancing its own P utilization efficiency, which may contribute to its successful invasion.