J-like protein family of Arabidopsis thaliana: the enigmatic cousins of J-domain proteins.

KEY MESSAGE: J-like proteins (JLPs) are emerging as ancillaries to the cellular chaperone network. They modulate functions of Hsp70:J-domain protein (JDP) systems in novel ways thereby having key roles in diverse plant processes. J-domain proteins (JDPs) form an obligate co-chaperone partnership with Hsp70s with their highly conserved J-domain to steer protein quality control processes in the cell. The HPD motif between helix II and helix III of the J-domain is crucial for JDP's interaction with Hsp70s. According to the most recent classification, J-like proteins (JLPs) form an extended class of the JDP family possessing a degenerate J-domain with the HPD motif non-conservatively replaced by other amino acid residues and hence are not able to interact with Hsp70s. Considering this most updated and acceptable JLP classification, we identified 21 JLPs in Arabidopsis thaliana that share a structurally conserved J-like domain (JLD), but lack the HPD motif. Analysis of publicly available gene expression data as well as real-time quantitative PCR performed for a few selected JLPs implicated some of these proteins in growth, development and stress response. Here, we summarize the current state of knowledge on plant JLPs and their involvement in vital plant cellular/metabolic processes, including chloroplast division, mitochondrial protein import and flowering. Finally, we propose possible modes of action for these highly elusive proteins and other DnaJ-related proteins (DNAJRs) in regulating the Hsp70 chaperone network.

Toxicity Mitigation of Textile Dye Reactive Blue 4 by Hairy Roots of Helianthus annuus and Testing Its Effect in In Vivo Model Systems.

An anthraquinone textile dye, Reactive Blue 4 (RB4), poses environmental health hazards. In this study, remediation of RB4 (30-110 ppm) was carried out by hairy roots (HRs). UV-visible spectroscopy and FTIR analysis showed that the dye undergoes decolourization followed by degradation. In addition, toxicity and safety analyses of the bioremediated dye were performed on Allium cepa and zebrafish embryos, which revealed lesser toxicity of the bioremediated dye as compared to untreated dye. For Allium cepa, the highest concentration, i.e., 110 ppm of the treated dye, showed less chromosomal aberrations with a mitotic index of 8.5 ± 0.5, closer to control. Two-fold decrease in mortality of zebrafish embryos was observed at the highest treated dye concentration indicating toxicity mitigation. A higher level of lipid peroxidation (LPO) was recorded in the zebrafish embryo when exposed to untreated dye, suggesting a possible role of oxidative stress-inducing mortality of embryos. Further, the level of LPO was significantly normalized along with the other antioxidant enzymes in embryos after dye bioremediation. At lower concentrations, mitigated samples displayed similar antioxidant activity comparable to control underlining the fact that the dye at lesser concentration can be more easily degraded than the dye at higher concentration.