Microplastics distinctly regulate cadmium accumulation and lipid homeostasis in maize: Mechanistic insights from membrane remodeling to gene expression.

Microplastics (MPs) derived from film mulching commonly exist in cadmium (Cd)-contaminated agricultural soil, but their impacts on Cd phytotoxicity are still controversial. Lipid remodeling is a key plant stress response, but whether conventional and biodegradable MPs differently regulate this process under Cd stress remain unclear. This study compared the effects of conventional polyethylene (PE) and biodegradable polylactic acid (PLA) MPs at two concentrations (0.1% and 1%) on Cd phytotoxicity in maize via a 35-day pot experiment, mainly focusing on the lipid homeostasis. Both individual and combined exposures to MPs and Cd inhibited maize growth and photosynthesis and induced oxidative stress. PE significantly reduced Cd concentration (20.06-38.71%) and uptake content (27.22-39.77%) in shoots and roots. PLA exhibited dose-dependent effects, where 0.1% addition increased Cd accumulation in roots, while 1% addition decreased it in shoots. These effects might be attributed to altered homeostasis of essential minerals (Ca, Fe, and Cu). Interaction analysis revealed that PE acted antagonistically with Cd at 0.1% and synergistically at 1%, while PLA showed antagonism at both concentrations. Integrated lipidomic and transcriptomic analyses identified five key regulatory genes (LACS4, GPAT6, LPP2, PLA2-III, and LPCAT4) significantly associated with 36 glycerophospholipids and glycerolipids, revealing that PE and PLA influenced maize molecular response via distinct lipid metabolism pathways under Cd stress. These findings demonstrate that conventional and biodegradable MPs differentially regulate Cd phytotoxicity in Cd‑contaminated soils through lipid remodeling, providing new insights for the safety assessment of agricultural film mulching.