Multi-metal tolerance of von Willebrand factor type D domain isolated from metal contaminated site by metatranscriptomics approach

Abstract

Environmental pollution through heavy metals is an upcoming universal problem that relentlessly endangers human health, biodiversity and ecosystems. Hence remediating these heavy metal pollutants from the environment by engineering soil microbiome through metatranscriptomics is befitting reply. In the present investigation, we have constructed size fractionated cDNA libraries from eukaryotic mRNA of cadmium (Cd) contaminated soil and screened for Cd tolerant genes by yeast complementation system by using Cd sensitive ycf1^Δ mutant. We are reporting one of the transformants PLCe10 (from library C, 1-4 kb) with potential tolerance towards Cd toxicity (40 μM-80 μM). Sequence analysis of PLCe10 transcript showed homology to von Willebrand factor type D domain (VWD) of vitellogenin-6 of Ascaris suum encoding 338 amino acids peptide. qPCR analysis revealed that PLCe10 induced in presence of Cd (32 fold) and also accumulated maximum amount of Cd at 60 μM Cd. This cDNA was further tested for its tolerance against other heavy metals like copper (Cu), zinc (Zn) and cobalt (Co). Heterologous complementation assays of cDNA PLCe10 showed a range of tolerance to Cu (150 μM-500 μM), Zn (10 mM-12 mM) and Co (2-4 mM). Results of the present study suggest that cDNA PLCe10 is one of the functional eukaryotic heavy metal tolerant genes present among the soil microbial community and could be exploited to rehabilitate metal contaminated sites.

Keywords: Heavy metal tolerance; Heavy metals; Metatranscriptomics; VWD; Vitellogenin.