Rare earth elements detoxification mechanism in the hyperaccumulator Dicranopteris linearis: [silicon-pectin] matrix fixation

Dicranopteris linearis is the best-known hyperaccumulator species of rare earth elements (REEs) and silicon (Si), capable of dealing with toxic level of REEs. Hence, this study aimed to clarify how D. linearis leaves cope with excessive REE stress, and whether Si plays a role in REE detoxification. The results show that lanthanum (La - as a representative of the REEs) stress led to decreased biomass and an increase of metabolism related to leaf cell wall synthesis and modification. However, the La stress-induced responses, especially the increase of pectinrelated gene expression level, pectin polysaccharides concentration, and methylesterase activity, could be mitigated by Si supply. Approximately 70% of the Si in D. linearis leaves interacted with the cell walls to form organosilicon Si-O-C linkages. The Si-modified cell walls contained more hydroxyl groups, leading to a more efficient REE retention compared to the Si-free ones. Moreover, this [Si-cell wall] matrix increased the pectin-La accumulation capacity by 64%, with no effect on hemicellulose-La and cellulose-La accumulation capacity. These results suggest that [Si-pectin] matrix fixation is key in REE detoxification in D. linearis, laying the foundation for the development of phytotechnological applications (e.g., REE phytomining) using this species in REEcontaminated sites.

Automated summary

Dicranopteris linearis is a hyperaccumulator plant of rare earth elements, and silicon plays a role in REE detoxification. The study found that Si supply can alleviate the damage caused by REE stress and increase the expression of pectin-related genes, pectin polysaccharide concentration, and methylesterase activity. Si-modified cell walls have higher REE retention capacity, and the [Si-pectin] matrix increases the accumulation capacity of pectin-REE. These findings lay the foundation for the development of phytotechnological applications using D. linearis in REE-contaminated sites.