Algae show promising potential in treating cadmium pollution, but the exploration of their molecular mechanisms is limited, which restricts the utilization of algal resources. Besides, investigating the mechanisms and components of heavy metal resistance in cyanobacteria can facilitate the development of algal resources. 

Transporters are believed to play a role in multi-substrate stress resistance and have been widely studied as targets for antibiotics and herbicides in bacteria and plants. However, the resistance mechanisms of various types of transporters in cyanobacteria to cadmium ions remain unclear.

In a study published in Ecotoxicology and Environmental Safety, a research team led by Prof. BI Yonghong from the Institute of Hydrobiology of the Chinese Academy of Sciences discovered a novel ABC transporter, Sll1725, which can mediate cadmium ion detoxification in Synechocystis sp. This study is the first to verify that a fourth type of transporter plays a role in detoxifying cadmium ions in model cyanobacteria and to explore its detoxification mechanism.

Through multi-omics analysis, researchers found that protein-to-mRNA ratios followed a Gaussian distribution, and cadmium ions affected transcriptional regulation. Besides, they revealed that under cadmium ion stress, multiple transporters were upregulated at both mRNA and protein levels, among which Sll1725, belonging to the fourth type of the ABC transporter, has the highest expression level. It was inferred that Sll1725 could alleviate cytotoxicity by excreting cadmium ions.

Using genetic methods, researchers found that the growth of the mutant strain (sll1725) was unaffected under normal conditions. However, under cadmium stress, both its growth and photosynthetic efficiency were significantly inhibited, and the mutant strain exhibited a weaker ability to excrete cadmium ions compared to the wild type.

Through molecular simulation analysis and inductively coupled plasma mass spectrometry determination, researchers found that adenosine triphosphate induced conformational changes in Sll1725, which led to cadmium ion transport due to the difference in binding free energy. Through heterologous expression, they discovered that Spirodela polyrhiza overexpressing sll1725 exhibited good cadmium tolerance.

This study provides a theoretical basis for applying algal genetic resources in cadmium pollution control, and identifies multiple potential genetic modification targets that could enhance algal tolerance. In addition, it shows that exploring the technical route of overexpressing prokaryotic genes in duckweed is conducive to the utilization of algal genetic resources.