An integrated transcriptome, metabolomic, and physiological investigation uncovered the underlying tolerance mechanisms of Monochoria korsakowii in response to acute/chronic cadmium exposure.

Identifying the physiological response and tolerance mechanism of wetland plants to heavy metal exposure can provide theoretical guidance for an early warning for acute metal pollution and metal-contaminated water phytoremediation. A hydroponic experiment was employed to investigate variations in the antioxidant enzyme activity, chlorophyll content, and photosynthesis in leaves of Monochoria korsakowii under 0.12 mM cadmium ion (Cd) acute (4 d) and chronic (21 d) exposure. Transcriptome and metabolome were analyzed to elucidate the underlying defensive strategies. The acute/chronic Cd exposure decreased chlorophyll a and b contents, and disturbed photosynthesis in the leaves. The acute Cd exposure increased catalase activity by 36.42%, while the chronic Cd exposure markedly increased ascorbate peroxidase, superoxide dismutase, and glutathione peroxidase activities in the leaves. A total of 2 685 differentially expressed genes (DEGs) in the leaves were identified with the plants exposed to the acute/chronic Cd contamination. In the acute Cd exposure treatment, DEGs were preferentially enriched in the plant hormone transduction pathway, followed by phenylrpopanoid biosynthesis. However, the chronic Cd exposure induced DEGs enriched in the biosynthesis of secondary metabolites pathway as priority. With acute/chronic Cd exposure, a total of 157 and 227 differentially expressed metabolites were identified in the leaves. Conjoint transcriptome and metabolome analysis indicated the plant hormone signal transduction pathway and biosynthesis of secondary metabolites was preferentially activated by the acute and chronic Cd exposure, respectively. The phenylpropanoid pathway functioned as a chemical defense, and the positive role of deoxyxylulose phosphate pathway in leaves against acute/chronic Cd exposure was impaired.