Identification of subfunctionalized aggregate-remodeling J-domain proteins inArabidopsis thaliana

Abstract

J-domain proteins (JDPs) are critical components of the cellular protein quality control machinery, playing crucial roles in preventing the formation and solubilizing cytotoxic protein aggregates. Bacteria, yeast and plants additionally have large, multimeric Hsp100-class disaggregases that resolubilize protein aggregates. JDPs interact with aggregated proteins and specify the aggregate-remodeling activities of Hsp70s and Hsp100s. However the aggregate-remodeling properties of plant JDPs are not well understood. Here we identify eight orthologs of Sis1 (an evolutionarily-conserved Class II JDP of budding yeast) in Arabidopsis thaliana with distinct aggregate-remodeling functionalities. Six of these JDPs associate with heat-induced protein aggregates in vivo and colocalize with Hsp101 at heat-induced protein aggregate centers. Consistent with a role in solubilizing cytotoxic protein aggregates, an atDjB3 mutant had defects in both solubilizing heat-induced aggregates and acquired thermotolerance as compared to wild-type seedlings. Next, we used yeast prions as protein aggregate models to show that the six JDPs have distinct aggregate-remodeling properties. Results presented in this study, as well as findings from phylogenetic analysis, demonstrate that plants harbour multiple, evolutionarily conserved JDPs with capacity to process a variety of protein aggregate conformers induced by heat and other stressors.

Inclusion of Hsp70 co-chaperone and RNA binding activities facilitate optimal function of spliceosomal disassembly factor Cwf23 in intron-richSchizosaccharomyces pombe

“…To ascertain the Hsp70 co-chaperone activity of Cwf23, we tested the functionality of its J-domain by exploiting a previously established genetic approach. The temperature sensitivity of budding yeast cells lacking the multi-functional JDP, Ydj1, is significantly rescued by heterologous expression of J-domain fragments of many different JDPs (Sahi & Craig, 2007b; Tak et al, 2023; Verma et al, 2017). As expected, expression of wild-type Cwf23 J-domain fragment (1-165 amino acids) rescued the temperature sensitivity of ydj1Δ cells at 30°C while H37Q did not (Fig 4C).…”

MsDjB4, a HSP40 Chaperone in Alfalfa (Medicago sativa L.), Improves Alfalfa Hairy Root Tolerance to Aluminum Stress

“…In Arabidopsis thaliana, atDjB7, which is ortholog to yeast Djp1, is involved in peroxisomal protein transport in association with cytosolic Hsp70 and contributes to plant survival under abiotic stress conditions [14,37]. One more type II J protein in Arabidopsis, atDjB3, has been found to possess the ability to remodel aggregated proteins and has been shown to enhance the acquired thermotolerance of plants [38]. Therefore, based on the sequence similarity and the involvement of Type II DnaJ proteins in various plant processes, it is reasonable to speculate that MsDjB4 may also participate in multiple biological processes in alfalfa, including stress responses and protein metabolism.…”

Cytosolic Class I J-domain proteins aid mitochondrial protein import and influence homeostasis inArabidopsis thaliana

“…Total protein was extracted from yeast cells following the protocol described earlier (Tak et al ., 2023). Briefly, 0.7-1.0 OD 600 equivalent cells were spun down, treated with 0.1 N NaOH and resuspended in SDS sample buffer.…”