AmTPS6 promotes trehalose biosynthesis to enhance the Cd tolerance in mangrove Avicennia marina

Cadmium (Cd) pollution poses a significant ecological risk to mangrove ecosystems. Trehalose has excellent potential to mitigate the adverse effects of heavy metals. Unfortunately, the mechanisms related to trehalose-mediated heavy metal tolerance in plants remain elusive. In the present study, we firstly found that Cd induced the accumulation of trehalose and the differential expression of trehalose biosynthesis genes in the roots of mangrove plant Avicennia marina. Then, we found that the application of exogenous trehalose could alleviate the negative effects of Cd on A. marina by phenotypic observation. In addition, photosynthetic parameters and cellular ultrastructure analyses demonstrated that exogenous trehalose could improve the photosynthesis and stabilize the chloroplast and nuclear structure of the leaves of A. marina. Besides, exogenous trehalose could inhibit the Cd 2+ influx from the root to reduce the Cd 2+ content in A. marina. Subsequently, substrate sensitivity assay combined with ion uptake analysis using yeast cells showed that several trehalose biosynthesis genes may have a regulatory function for Cd 2+ transport. Finally, we further identified a positive regulatory factor, AmTPS6, which enhances the Cd tolerance in transgenic Arabidopsis thaliana. Taken together, these findings provide new understanding to the mechanism of Cd tolerance in mangrove A. marina at trehalose aspect and a theoretical basis for the conservation of mangroves in coastal wetlands.