Promoted metabolic remolding by overexpression of AspAT9 ameliorates cadmium toxicity in Arabidopsis

Cadmium (Cd) is a toxic heavy metal that poses a serious threat to crop safety and human health. Aspartate aminotransferase (AspAT) is a prime enzyme engaged in amino acid metabolism, contributing essential metabolic substances for plant growth and acclimatization to various stresses. In this study, we identified a novel AspAT9 gene with high responsiveness to Cd stress from poplar 'Nanlin895' and subsequently transformed it into Arabidopsis. The resulting transgenic AspAT9-1 plants (designated A9) and wild-type (WT) Arabidopsis were subjected to Cd treatment (T) or maintained under control conditions (CK). Phenotypic assessments showed that A9 plants displayed greater resistance to Cd stress compared to WT, as evidenced by their stay-green trait and higher biomass. Subsequent metabolism measurement revealed that A9 plants accumulated more Cd in their roots than WT. Meanwhile, the content of various proteinogenic amino acids, Cd-chelating compounds, such as lignin and phytochelatins (PCs), along with antioxidants like glutathione (GSH) and chlorophyll in A9-T exceeded WT-T. Further RNA-seq analysis uncovered significant transcriptional changes in genes implicated in aspartate-glutamate metabolism, antioxidant systems, phenylpropanoid biosynthesis, transporters, and photosynthesis activities. Our findings demonstrate the beneficial effect of overexpressing AspAT9 on Cd phytoextraction, highlights its potential as a valuable genetic resource for phytoremediation applications.