Microbial communities in Iron Plaques of Rice Plants Raw sequence reads

Iron (Fe) plaques form on rice root surfaces due to the oxidation of Fe(II) to Fe(III). This process is facilitated by oxygen released from the root's aerenchyma under flooded, anaerobic conditions. Fe plaques play a pivotal role in immobilizing heavy metal(loids), thereby mitigating their accumulation in rice plants. However, the principal factors influencing Fe plaque formation and its adsorption capacity for heavy metal(loids) throughout the rice plant's lifecycle remain incompletely understood. Thus, this study investigates the dynamics of Fe plaque formation and its ability to adsorb cadmium (Cd) and arsenic (As) across different growth stages, aiming to identify the key drivers behind these processes. Our findings reveal that Fe plaque formation and As adsorption follow a similar trend, peaking during the tillering stage. In contrast, Cd adsorption by Fe plaques decreases from the tillering to the maturing stage. The rate of radial oxygen loss (ROL), plaque-associated microbes, including organic matter (OM)-degrading bacteria, Fe(III)-reducing bacteria (FeRB), and rhizosphere Fe(II)-oxidizing bacteria (FeOB), are the primary drivers of Fe plaque formation. Similarly, the adsorption of As by Fe plaques is principally determined by the rate of ROL and the quantity of Fe plaques, with subsequent effects from arsenate-reducing bacteria and OM-degrading bacteria. By contrast, the adsorption of Cd onto Fe plaques is primarily affected by the competitive adsorption of ammonium (NH4+) and the synergistic adsorption of arsenate (As(V)) on Fe plaques. Moreover, the presence of both OM-degrading and nitrite-oxidizing bacteria plays a significant role in the adsorption of Cd on Fe plaques. The findings provide significant insights into the development of iron plaques and their absorption of heavy metal(loids) over the life cycle of rice plants.