Identification of a New Target slr0946 of the Response Regulator Sll0649 Involving Cadmium Tolerance in Synechocystis sp. PCC 6803

Abstract

Survival of photosynthetic cyanobacteria is challenged by environmental contaminations like heavy metals. Among them, deciphering the regulatory mechanisms for cadmium (Cd) in cyanobacteria would facilitate the construction of Cd-resistant strains. In this study, the DNA-Affinity-Purified-chromatin immunoprecipitation assay was employed to identify the direct targets of Sll0649, which was a Cd²⁺-related response regulator identified in our previous work in model cyanobacteria <i>Synechocystis</i> sp. PCC 6803. As a result, the promoter region of <i>slr0946</i> encoding the arsenate reductase was enriched fourfolds by quantitative real time PCR analysis. Further, deletion of <i>slr0946</i> led to a sensitive phenotype to Cd²⁺ stress compared with the wild type (WT) and the sensitive phenotype of Δ<i>slr0946</i> could be rescued by complementation assay via introducing <i>slr0946</i> back into Δ<i>slr0946</i>. Finally, individually overexpression of <i>slr0946</i> as well as two Cd²⁺-related genes identified priviously (i.e., <i>sll1598</i> and <i>slr0798</i>) in WT could significantly improve the tolerance of <i>Synechocystis</i> sp. PCC 6803 to Cd²⁺. This study provided a better understanding of the tolerance mechanism to Cd²⁺ in cyanobacteria and also feasible strategies for tolerance modifications to heavy metals in the future.