Isolation of multi-metal tolerant ubiquitin fusion protein from metal polluted soil by metatranscriptomic approach

Abstract

Release of heavy metals into the soil pose a significant threat to the environment and public health because of their toxicity accumulation in the food chain and persistence in nature. The potential of soil microbial diversity of cadmium (Cd) contaminated site was exploited through functional metatranscriptomics by construction of cDNA libraries A (0.1-0.5 kb), B (0.5-1.0 kb), and C (1-4 kb) of variable size, from the eukaryotic mRNA. The cDNA library B was further screened for cadmium tolerant transcripts through yeast complementation system. We are reporting one of the transformants ycf1^ΔPLBe1 capable of tolerating high concentrations of Cd (40 μM - 80 μM). Sequence analysis revealed that PLBe1 cDNA showed homology with ubiquitin domain containing protein fused with AN1 type zinc finger protein of Acanthameoba castellani. Further, this cDNA was tested for its tolerance towards other heavy metals such as copper (Cu), zinc (Zn) and cobalt (Co). Functional complementation assay of cDNA PLBe1 showed a range of tolerance towards copper (150 μM - 300 μM), zinc (10 mM - 12 mM) and cobalt (2 mM - 4 mM). This study promulgates PLBe1 as credible member of multi-metal tolerant gene in the eukaryotic soil microbial community and can be used as potential member to revitalise the heavy metal contaminated sites or can be used as a biomarker to detect heavy metal contamination in the soil environment.

Keywords: AN1 type zinc finger protein; Functional Metatranscriptomics; Functional complementation; Heavy metals; Ubiquitin fusion protein.