Plant growth promoting endophyte promotes cadmium accumulation in Solanum nigrum L. by regulating plant homeostasis

The homeostasis regulating mechanism of endophyte enhancing cadmium (Cd) extraction by hyperaccumulator is poorly understood. Here, an endophyte strain E3 that belonged to Pseudomonas was screened from Cd hyperaccumulator Solanum nigrum L., which significantly improved the Cd phytoextraction efficiency of S. nigrum by 40.26%. The content and translocation factor of nutrient elements indicated that endophyte might regulate Cd accumulation by affecting the uptake and transport of magnesium and iron in S. nigrum. Gene transcriptional expression profile further revealed that SnMGT, SnIRT1, and SnIRT2, etc., were the key genes involved in the regulation of S. nigrum elements uptake by endophyte. However, changes in elemental homeostasis did not negatively affect plant growth. Endophyte inoculation promoted plant growth by fortifying photosynthesis as well as recruiting specific bacteria in S. nigrum endosphere, e.g., Pseudonocardiaceae, Halomonas. Notably, PICRUSt2 analysis and biochemical characterization jointly suggested that endophyte regulated starch degradation in S. nigrum leaves to maintain photosynthetic balance. Our results demonstrated that microecological

Automated summary

This study revealed the homeostasis regulating mechanism of endophyte enhancing cadmium extraction by hyperaccumulator plants. The endophyte improved the phytoextraction efficiency of the hyperaccumulator by affecting nutrient element uptake and transport as well as regulating key gene expression. Additionally, endophyte inoculation promoted plant growth and regulated starch degradation to maintain photosynthetic balance.