Plant-rhizosphere microbe interactions and their roles in nitrogen cycles under periodic flooding: From cooperation mechanisms to ecological responses
Tianpeng Gao, Yi Li, Nan Yang, Wei Xiong, Xiaodan Liang, Yingjie Wang
Abstract
Periodic flooding in riparian zones induces significant environmental heterogeneity that sustains unique plant-microbe symbioses, functioning as key regulators of nitrogen (N) cycling under intensifying anthropogenic nutrient inputs. While extensive studies have characterized diversity and functional dynamics of rhizosphere microbial communities participating in N cycles, they often overlook the roles of host plants and lack comprehensive elucidation of both assembly mechanisms underlying riparian plant-rhizosphere microbe symbioses and their regulation on N cycling under periodic flooding. Here, we systematically synthesize current advances in deciphering formation mechanisms and functional dynamics of riparian plant-rhizosphere microbe symbioses through molecular perspectives, with particular focus on their roles in N cycles. Specifically, we first clarify the mechanisms governing root exudates production and release in riparian systems, followed by detailed examination of microbial colonization strategies—including biofilm formation and mycorrhizal associations—that are mechanistically mediated by root-derived signaling molecules. Building on these insights, we propose a coevolutionary framework where plant-regulated exudates, rhizosphere oxygen gradients, and microbial enzyme activities collectively modulate N cycling under hydrological fluctuations. Furthermore, we delineate how hydrodynamics, soil properties, exogenous pollutant inputs, and iron plaques interactively shape these symbiotic relationships and associated N transformations. Additionally, we outline prioritized research directions for advancing technological innovations and multidimensional mechanistic investigations to deepen molecular-level understanding of plant-microbe symbioses and their regulatory controls on N cycling in riparian zones. By integrating theoretical advances, this review aims to guide riparian ecosystem conservation strategies and precision management of nitrogen flux dynamics, thereby contributing to strategic protection of global freshwater quality.