The growth of hyperaccumulator plants is often compromised by increased toxicity of metals like cadmium (Cd). However, extraction of such metals from the soil can be enhanced by endophytic microbial association. Present study was aimed to elucidate the potential of microbe-assisted Cd phytoextraction in hyperaccumulator Solanum nigrum plants and their interactions under varied Cd concentrations. An endophytic bacteria Serratia sp. RSC-14 was isolated from the roots of S. nigrum. In addition to Cd tolerance up to 4 mM, the RSC-14 exhibited phosphate solubilization and secreted plant growth-promoting phytohormones such as indole-3-acetic acid (54 μg/mL). S. nigrum plants were inoculated with RSC-14 and were grown in different concentrations of Cd (0, 10, and 30 mg Cd kg(-1) sand). Results revealed that Cd treatment caused significant cessation in plant growth, biomass, and chlorophyll content, whereas significantly higher malondialdehyde (MDA) and electrolyte production in leaves were observed in a dose-dependent manner. Conversely, RSC-14 inoculation relived the toxic effects of Cd-induced stress by significantly increasing root/shoot growth, biomass production, and chlorophyll content and decreasing MDA and electrolytes contents. Ameliorative effects on host growth were also observed by the regulation of metal-induced oxidative stress enzymes such as catalase, peroxidase, and polyphenol peroxidase. Activities of these enzymes were significantly reduced in RSC-14 inoculated plants as compared to control plants under Cd treatments. The lower activities of stress responsive enzymes suggest modulation of Cd stress by RSC-14. The current findings support the beneficial uses of Serratia sp. RSC-14 in improving the phytoextraction abilities of S. nigrum plants in Cd contamination.

The improvement of biopesticides for use in the agriculture industry requires an understanding of the biological-and ecological principles underlying their behavior in natural environments. The nuclear genomes of members of the genus Trichoderma, which are representative fungal biocontrol agents, have been actively studied in relation to the unique characteristics of these species as effective producers of CAZymes/secondary metabolites and biopesticides, but their mitochondrial genomes have received much less attention. In this study, the mitochondrial genome of Trichoderma atroviride (Hypocreales, Sordariomycetes), which targets wood-decaying fungal pathogens and has the ability to degrade chemical fungicides, was assembled de novo. A 32,758 bp circular DNA molecule was revealed with specific features, such as a few more protein CDS and trn genes, two homing endonucleases (LAGLIDADG-/GIY-YIG-type), and even a putative overlapping tRNA gene, on a closer phylogenetic relationship with T. gamsii among hypocrealean fungi. Particularly, introns were observed with several footprints likely to be evolutionarily associated with the intron dynamics of the Trichoderma mitochondrial genomes. This study is the first to report the complete de novo mitochondrial genome of T. atroviride, while comparative analyses of Trichoderma mitochondrial genomes were also conducted from the perspective of mitochondrial evolution for the first time.