Table 3.

Published metatranscriptomics studies on different soil ecosystems

Soil Sample	RNA extraction method	mRNA enrichment	cDNA preparation	Sequencing/Screening	Size of dataset	Significant findings	Reference
Forest soil	Guanidine isothiocyanate, bead-beating,	Poly(A) tail mRNA captured by affinity capture	Poly-dT primer (SMART cDNA kit,	Sanger sequencing	119 clone sequences	Eukaryotic diversity, novel enzymes	Bailly et al. (2007)
Sandy, Nutrient-poor soil	CTAB, P/C/I Lysing matrix E tube (Q-Biogene) PEG 8000	None	Random primer	Pyrosequencing	314,041	CO2 fixation and ammonia oxidizers enzymes	Urich et al. (2008)
Sugar maple forest soil	Bead beating,, 8-hydroxyquinoline, RNA/ DNA Midi kit (Qiagen)	None	Selective amplification of eukaryotic mRNA by (SMART cDNA kit	Screening by auxotrophy-complementing genes in yeast	10 transformed yeast sequenced	Acid phosphatase, Imidazole glycerol-phosphate dehydratase	Kellner et al. (2011)
Spruce forest	Guanidine isothiocyanate, bead-beating	Affinity capture of polyadenylated mRNA on poly-dT coated paramagnetic beads	Poly-dT primer (SMART cDNA kit	Screening by auxotrophy-complementing genes in yeast	7.7 × 105 screened transformants, 25 putative genes	Novel fungal oligopeptide transporter	Damon et al. (2011)
Beech and Spruce forest	Guanidine isothiocyanate, bead-beating	Poly-dT beads for separating eukaryotic polyadenylated RNA	SMART cDNA Library Construction Kit (Clontech)	Sanger sequencing	10,000 each	Eukaryotic Diversity, novel enzymes for organic matter degradation	Damon et al. (2012)
Soil near metal smelter	Guanidine isothiocyanate, bead-beating	Poly(A) tail mRNA captured by affinity capture	Poly-dT primer (SMART cDNA kit,	Sanger sequencing	30 k cDNA for each soil sample	Metal tolerant genes	Lehembre et al. (2013)
Agro forestry contaminated soil	RNA isolation Kit (Mo Bio labs)	None	Selective amplification of eukaryotic mRNA by (SMART cDNA kit	Screening by auxotrophy-complementing genes in yeast	0.5 kb- 1.0 kb size library	Ubiquitin fusion protein/Heavy metal tolerance gene	Thakur et al. (2018)
Agro forestry contaminated soil	RNA isolation Kit (Mo Bio labs)	None	Selective amplification of eukaryotic mRNA by (SMART cDNA kit	Screening by auxotrophy-complementing genes in yeast	1–4 kb size library	VWD like protein/multi-metal tolerant	Thakur et al. (2019)
Metal contaminated forest soil	RNA isolation Kit (Mo Bio labs)	None	Selective amplification of eukaryotic mRNA by Mint2 cDNA kit	Screening by auxotrophy-complementing genes in yeast	1–4 kb size library	Aldehyde dehydrogenase conferring metal tolerance	Mukherjee et al. (2019a)
Metal contaminated forest soil	RNA isolation Kit (Mo Bio labs)	None	Selective amplification of eukaryotic mRNA by Mint2 cDNA kit	Screening by auxotrophy-complementing genes in yeast	1–4 kb size library	Serine protease inhibitor conferring metal tolerance	Mukherjee et al. (2019b)