DnaJ Protein Research Articles

Altered Function of the DnaJ Family Cochaperone DNJ-17 Modulates Locomotor Circuit Activity in a Caenorhabditis elegans Seizure Model.

The highly conserved cochaperone DnaJ/Hsp40 family proteins are known to interact with molecular chaperone Hsp70, and can regulate many cellular processes including protein folding, translocation, and degradation. In studies of Caenorhabditis elegans locomotion mutants, we identified a gain-of-function (gf) mutation in dnj-17 closely linked to the widely used e156 null allele of C. elegans GAD (glutamic acid decarboxylase) unc-25. dnj-17 encodes a DnaJ protein orthologous to human DNAJA5. In C. elegans DNJ-17 is a cytosolic protein and is broadly expressed in many tissues. dnj-17(gf) causes a single amino acid substitution in a conserved domain, and behaves as a hypermorphic mutation. The effect of this dnj-17(gf) is most prominent in mutants lacking GABA synaptic transmission. In a seizure model caused by a mutation in the ionotropic acetylcholine receptor acr-2(gf), dnj-17(gf) exacerbates the convulsion phenotype in conjunction with absence of GABA. Null mutants of dnj-17 show mild resistance to aldicarb, while dnj-17(gf) is hypersensitive. These results highlight the importance of DnaJ proteins in regulation of C. elegans locomotor circuit, and provide insights into the in vivo roles of DnaJ proteins in humans.

Proteomic analysis in the induction of nodular cluster cultures in the bromeliad Vriesea reitzii Leme and Costa

Nodular cluster cultures (NCs) are globular organogenic clumps with a high regenerative potential applied to the large-scale micropropagation of bromeliads. In the present work, we identified differentially expressed proteins involved in the induction of NCs from seeds and leaf explants of the Brazilian native bromeliad Vriesea reitzii. Those explants were inoculated into Murashige and Skoog (MS) liquid medium free of plant growth regulators (PGR). To promote the induction of NCs, the seeds were grown in MS medium supplemented with 4 μM α-naphthaleneacetic acid (NAA), and the leaf segments in MS medium supplemented with 4 μM NAA and 2 μM 6-benzylaminopurine (BAP). After 21 days in culture, samples of each type of explant were collected for histological analysis and protein extraction. Proteomic analysis was performed by two-dimensional (2D) electrophoresis and protein identification by MALDI-TOF–TOF mass spectrometry. Enhanced protein content and number of detected spots on cultures supplemented with PGR were observed as compared to the cultures maintained in PGR-free MS culture medium. Five differentially expressed proteins were identified during the induction of NCs: heat shock 22 kDa, chaperone protein dnaJ 50, S-adenosylmethionine synthase 3, UDP-arabinopyranose mutase 1, and 14-3-3-like protein E. Such proteins are involved in stress response, cell metabolism, and cell division. The ability to regulate the effects of stress conditions in which the explants were subjected shows the presence of competent tissues for the acquisition of the morphogenic route associated to the induction of NCs.

A novel nuclear DnaJ protein, DNAJC8, can suppress the formation of spinocerebellar ataxia 3 polyglutamine aggregation in a J-domain independent manner

Polyglutamine (polyQ) diseases comprise neurodegenerative disorders caused by expression of expanded polyQ-containing proteins. The cytotoxicity of the expanded polyQ-containing proteins is closely associated with aggregate formation. In this study, we report that a novel J-protein, DNAJ (HSP40) Homolog, Subfamily C, Member 8 (DNAJC8), suppresses the aggregation of polyQ-containing protein in a cellular model of spinocerebellar ataxia type 3 (SCA3), which is also known as Machado-Joseph disease. Overexpression of DNAJC8 in SH-SY5Y neuroblastoma cells significantly reduced the polyQ aggregation and apoptosis, and DNAJC8 was co-localized with the polyQ aggregation in the cell nucleus. Deletion mutants of DNAJC8 revealed that the C-terminal domain of DNAJC8 was essential for the suppression of polyQ aggregation, whereas the J-domain was dispensable. Furthermore, 22-mer oligopeptide derived from C-termilal domain could suppress the polyQ aggregation. These results indicate that DNAJC8 can suppress the polyQ aggregation via a distinct mechanism independent of HSP70-based chaperone machinery and have a unique protective role against the aggregation of expanded polyQ-containing proteins such as pathogenic ataxin-3 proteins.

Arabidopsis AtDjA3 Null Mutant Shows Increased Sensitivity to Abscisic Acid, Salt, and Osmotic Stress in Germination and Post-germination Stages.

DnaJ proteins are essential co-chaperones involved in abiotic and biotic stress responses. Arabidopsis AtDjA3 gene encodes a molecular co-chaperone of 420 amino acids, which belongs to the J-protein family. In this study, we report the functional characterization of the AtDjA3 gene using the Arabidopsis knockout line designated j3 and the 35S::AtDjA3 overexpression lines. Loss of AtDjA3 function was associated with small seed production. In fact, j3 mutant seeds showed a reduction of 24% in seed weight compared to Col-0 seeds. Expression analysis showed that the AtDjA3 gene was modulated in response to NaCl, glucose, and abscisic acid (ABA). The j3 line had increased sensitivity to NaCl and glucose treatments in the germination and cotyledon development in comparison to parental Col-0. Furthermore, the j3 mutant line exhibited higher ABA sensitivity in comparison to parental Col-0 and 35S::AtDjA3 overexpression lines. In addition, we examined the expression of ABI3 gene, which is a central regulator in ABA signaling, in j3 mutant and 35S::AtDjA3 overexpression lines. Under 5 μM ABA treatment at 24 h, j3 mutant seedlings displayed higher ABI3 expression, whereas in 35S::AtDjA3 overexpression lines, ABI3 gene expression was repressed. Taken together, these results demonstrate that the AtDjA3 gene is involved in seed development and abiotic stress tolerance.

Chaperone-Mediated Mechanical Protein Folding at the Single Molecule Level

DnaK, DnaJ and GrpE heat shock proteins form the main conserved chaperone system in Escherichia coli. Such a complex chaperone system participates in the correct folding of emergent polypeptides in the ribosome to ensure that they reach their native structure, while preventing the aggregation of proteins under stress conditions in the cell. It is well known from bulk experiments that DnaK and DnaJ accomplish these functions by binding to both unfolded and partially unfolded protein substrates. However, the extended protein conformations that characterise the nascent proteins in the ribosome are rarely accessible by biochemistry denaturing experiments. Moreover, the detailed conformation of the substrates required for an optimal chaperone binding still remains controversial. Here we use single molecule force-clamp spectroscopy AFM to study the effect of molecular chaperones on the mechanical folding of individual proteins. This approach enables to monitor the individual folding trajectories from highly extended states, and to dissect the different conformational ensembles visited by the single protein during its folding pathway. Our experiments reveal that DnaJ binds to the unfolded state of Ubiquitin (which contains the consensus binding sequence GKQLEDG) with more affinity than to the molten globule, collapsed state. DnaJ binding blocks ubiquitin refolding by decreasing its folding efficiency by over 40%, thus highlighting its “holdase” functionality. By contrast, DnaK presents instead a higher affinity for the molten globule conformations. Crucially, both proteins, together with GrpE, readily increase the refolding of Ubiquitin by over 10%, within an ATP-mediated process. Altogether, our nanomechanical experiments demonstrate that the binding of different chaperones to a unique substrate is highly conformation-dependent, enabling us to postulate a kinetic scheme that underlies the synergetic functionality of a complex chaperone system, at the single molecule level.

Validation of candidate reference genes for gene expression normalization in Buchloe dactyloides using quantitative real-time RT-PCR

The proper selection of reference genes to normalize the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) results under special experimental conditions is crucial for quantifying gene expression. A systematic reference gene screening was performed using SYBR green qRT-PCR on 10 candidate genes in 27 biological samples of various photoperiodic treatments and different tissues in Buchloe dactyloides. Analysis by 3 different qRT-PCR methods (GeNorm, NormFinder, and BestKeeper) indicated that a combination of beta actin (β-ACT), dnaj protein gene (DNAJ) and protein phosphatase 2a (PP2A) were the most suitable reference genes across all samples examined. While the expression of the β-ACT and PP2A were the most stable genes in the long day (LD)-treated plant samples, glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH) and β-ACT performed more stably in short day (SD) and constant dark (24D)-treated plant samples. β-ACT and PP2A displayed the most stable expression under constant light (24L) condition. β-ACT and DNAJ were the optimal reference genes in different tissues. Furthermore, examination of relative expression of a functional gene long hypocotyl 5 (HY5) in LD-treated RNA samples demonstrated additional reference genes contribute to accurate quantitative expression analysis. This study will help the selection of the most stable reference genes for accurate gene expression studies in B. dactyloides.

Genome-wide Identification and Expression Pattern Analysis of the DnaJ Protein Family in Gossypium raimondii under Salt Stress Using a Bioinformatics Method

Genome-wide Identification and Expression Pattern Analysis of the DnaJ Protein Family in Gossypium raimondii under Salt Stress Using a Bioinformatics Method

Evaluation of the amyloid beta-GFP fusion protein as a model of amyloid beta peptides-mediated aggregation: a study of DNAJB6 chaperone.

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by the accumulation and aggregation of extracellular amyloid β (Aβ) peptides and intracellular aggregation of hyper-phosphorylated tau protein. Recent evidence indicates that accumulation and aggregation of intracellular amyloid β peptides may also play a role in disease pathogenesis. This would suggest that intracellular Heat Shock Proteins (HSP) that maintain cellular protein homeostasis might be candidates for disease amelioration. We recently found that DNAJB6, a member of DNAJ family of heat shock proteins, effectively prevented the aggregation of short aggregation-prone peptides containing large poly glutamines (associated with CAG repeat diseases) both in vitro and in cells. Moreover, recent in vitro data showed that DNAJB6 can delay the aggregation of Aβ42 peptides. In this study, we investigated the ability of DNAJB6 to prevent the aggregation of extracellular and intracellular Aβ peptides using transfection of human embryonic kidney 293 (HEK293) cells with Aβ-green fluorescent protein (GFP) fusion construct and performing western blotting and immunofluorescence techniques. We found that DNAJB6 indeed suppresses Aβ-GFP aggregation, but not seeded aggregation initiated by extracellular Aβ peptides. Unexpectedly and unlike what we found for peptide-mediated aggregation, DNAJB6 required interaction with HSP70 to prevent the aggregation of the Aβ-GFP fusion protein and its J-domain was crucial for its anti-aggregation effect. In addition, other DNAJ proteins as well as HSPA1a overexpression also suppressed Aβ-GFP aggregation efficiently. Our findings suggest that Aβ aggregation differs from poly glutamine (Poly Q) peptide induced aggregation in terms of chaperone handling and sheds doubt on the usage of Aβ-GFP fusion construct for studying Aβ peptide aggregation in cells.

The DnaJ OsDjA7/8 is essential for chloroplast development in rice (Oryza sativa)

DnaJ proteins belong to chaperones of Hsp40 family that ubiquitously participate in various cellular processes. Previous studies have shown chloroplast-targeted DnaJs are involved in the development of chloroplast in some plant species. However, little is known about the function of DnaJs in rice, one of the main staple crops. In this study, we characterized a type I DnaJ protein OsDjA7/8. We found that the gene OsDjA7/8 was expressed in all collected tissues, with a priority in the vigorous growth leaf. Subcellular localization revealed that the protein OsDjA7/8 was mainly distributed in chloroplast. Reduced expression of OsDjA7/8 in rice led to albino lethal at the seedling stage. Transmission electron microscopy observation showed that the chloroplast structures were abnormally developed in the plants silenced for OsDjA7/8. In addition, the transcriptional expression of the genes tightly associated with the development of chloroplast was deeply reduced in the plants silenced for OsDjA7/8. Collectively, our study reveals that OsDjA7/8 encodes a chloroplast-localized protein and is essential for chloroplast development and differentiation in rice.

Rme-8 depletion perturbs Notch recycling and predisposes to pathogenic signaling.

Notch signaling is a major regulator of cell fate, proliferation, and differentiation. Like other signaling pathways, its activity is strongly influenced by intracellular trafficking. Besides contributing to signal activation and down-regulation, differential fluxes between trafficking routes can cause aberrant Notch pathway activation. Investigating the function of the retromer-associated DNAJ protein Rme-8 in vivo, we demonstrate a critical role in regulating Notch receptor recycling. In the absence of Rme-8, Notch accumulated in enlarged tubulated Rab4-positive endosomes, and as a consequence, signaling was compromised. Strikingly, when the retromer component Vps26 was depleted at the same time, Notch no longer accumulated and instead was ectopically activated. Likewise, depletion of ESCRT-0 components Hrs or Stam in combination with Rme-8 also led to high levels of ectopic Notch activity. Together, these results highlight the importance of Rme-8 in coordinating normal endocytic recycling route and reveal that its absence predisposes toward conditions in which pathological Notch signaling can occur.

Identification and characterization of a DnaJ gene from red alga Pyropia yezoensis (Bangiales, Rhodophyta)

Members of the DnaJ family are proteins that play a pivotal role in various cellular processes, such as protein folding, protein transport and cellular responses to stress. In the present study, we identified and characterized the full-length DnaJ cDNA sequence from expressed sequence tags of Pyropia yezoensis (PyDnaJ) via rapid identification of cDNA ends. This cDNA encoded a protein of 429 amino acids, which shared high sequence similarity with other identified DnaJ proteins, such as a heat shock protein 40/DnaJ from Pyropia haitanensis. The relative mRNA expression level of PyDnaJ was investigated using real-time PCR to determine its specific expression during the algal life cycle and during desiccation. The relative mRNA expression level in sporophytes was higher than that in gametophytes and significantly increased during the whole desiccation process. These results indicate that PyDnaJ is an authentic member of the DnaJ family in plants and red algae and might play a pivotal role in mitigating damage to P. yezoensis during desiccation.

Isoform-selective Genetic Inhibition of Constitutive Cytosolic Hsp70 Activity Promotes Client Tau Degradation Using an Altered Co-chaperone Complement

The constitutively expressed heat shock protein 70 kDa (Hsc70) is a major chaperone protein responsible for maintaining proteostasis, yet how its structure translates into functional decisions regarding client fate is still unclear. We previously showed that Hsc70 preserved aberrant Tau, but it remained unknown if selective inhibition of the activity of this Hsp70 isoform could facilitate Tau clearance. Using single point mutations in the nucleotide binding domain, we assessed the effect of several mutations on the functions of human Hsc70. Biochemical characterization revealed that one mutation abolished both Hsc70 ATPase and refolding activities. This variant resembled the ADP-bound conformer at all times yet remained able to interact with cofactors, nucleotides, and substrates appropriately, resembling a dominant negative Hsc70 (DN-Hsc70). We then assessed the effects of this DN-Hsc70 on its client Tau. DN-Hsc70 potently facilitated Tau clearance via the proteasome in cells and brain tissue, in contrast to wild type Hsc70 that stabilized Tau. Thus, DN-Hsc70 mimics the action of small molecule pan Hsp70 inhibitors with regard to Tau metabolism. This shift in Hsc70 function by a single point mutation was the result of a change in the chaperome associated with Hsc70 such that DN-Hsc70 associated more with Hsp90 and DnaJ proteins, whereas wild type Hsc70 was more associated with other Hsp70 isoforms. Thus, isoform-selective targeting of Hsc70 could be a viable therapeutic strategy for tauopathies and possibly lead to new insights in chaperone complex biology.

Mechanism of Plant Growth Promoting Activity of Burkholderia Species

Application of plant growth promoting rhizobacteria (PGPR) to boost up production and reduce pathogenesis is an imminent approach in agriculture. One of the PGPR (RR18) was found to have best plant growth promoting characteristics among 41 PGPR shortlisted from the 162 bacteria isolated from the groundnut rhizosphere. RR18 reduced disease incidence and increased germination of groundnut seeds in presence of A. niger. RR18 was found to induce systemic resistance in A. hypogaea L. as it induced chitinase, ß – 1,3- glucanase, phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, lipoxygenase and jasmonic acid. Investigation of the specific mechanism by a comparative 2D gel electrophoresis of bacteria treated and untreated groundnut seedlings revealed induction of several proteins, two of them very prominently seen were- 60 kD and 56 kD proteins. These proteins were identified as Phospho-2-dehydro-3-deoxyheptonate aldolase 1 and auxilin related protein 1 using MALDI TOF and Mascot analysis. Phospho-2-dehydro-3-deoxyheptonate aldolase 1 is reported to synthesize secondary metabolites derived from intermediates of the pre-chorismate pathway up to shikimate. Auxilin related protein 1 belongs to DnaJ protein family and reported to be involved in protein folding, protein transport and plant growth promoting activity. 16S rDNA sequence of RR18 showed 99 % homology to Burkholderia species.

Comparative proteomic analysis of gamma-aminobutyric acid responses in hypoxia-treated and untreated melon roots

Hypoxia is one of the main environmental stresses that accounts for decreasing crop yield. To further investigate the mechanisms whereby exogenous GABA alleviates hypoxia injury to melon seedlings, a comparative proteomic analysis was performed using roots subjected to normal aeration and hypoxia conditions with or without GABA (5mM). The results indicated that protein spots on gels after hypoxia and hypoxia+GABA treatment were significantly changed. Three “matched sets” were analyzed from four treatments, and 13 protein spots with large significant differences in expression were identified by MALDI-TOF/TOF mass spectrometry. Exogenous GABA treatment enhanced the expression of protein in cytosolic phosphoglycerate kinase 1, exaA2 gene product, dnaJ and myb-like DNA-binding domain-containing proteins, as well as elongation factor-1 alpha and hypothetical proteins in hypoxia-induced roots. However, the hypoxia+GABA treated roots had a significantly lower expression of proteins including malate dehydrogenase, nucleoside diphosphate kinase, disease resistance-like protein, disulfide isomerase, actin, ferrodoxin NADP oxidoreductase, glutathione transferase, netting associated peroxidase. This paper describes the effect of GABA on melon plants under hypoxia-induced stress using proteomics, and supports the alleviating function of GABA in melon plants grown under hypoxic conditions.

A tomato chloroplast-targeted DnaJ protein protects Rubisco activity under heat stress.

Photosynthesis is one of the biological processes most sensitive to heat stress in plants. Carbon assimilation, which depends on ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), is one of the major sites sensitive to heat stress in photosynthesis. In this study, the roles of a tomato (Solanum lycopersicum) chloroplast-targeted DnaJ protein (SlCDJ2) in resisting heat using sense and antisense transgenic tomatoes were examined. SlCDJ2 was found to be uniformly distributed in the thylakoids and stroma of the chloroplasts. Under heat stress, sense plants exhibited higher chlorophyll contents and fresh weights, and lower accumulation of reactive oxygen species (ROS) and membrane damage. Moreover, Rubisco activity, Rubisco large subunit (RbcL) content, and CO2 assimilation capacity were all higher in sense plants and lower in antisense plants compared with wild-type plants. Thus, SlCDJ2 contributes to maintenance of CO2 assimilation capacity mainly by protecting Rubisco activity under heat stress. SlCDJ2 probably achieves this by keeping the levels of proteolytic enzymes low, which prevents accelerated degradation of Rubisco under heat stress. Furthermore, a chloroplast heat-shock protein 70 was identified as a binding partner of SlCDJ2 in yeast two-hybrid assays. Taken together, these findings establish a role for SlCDJ2 in maintaining Rubisco activity in plants under heat stress.

Submicroscopic and asymptomatic Plasmodium falciparum and Plasmodium vivax infections are common in western Thailand - molecular and serological evidence.

BackgroundMalaria is a public health problem in parts of Thailand, where Plasmodium falciparum and Plasmodium vivax are the main causes of infection. In the northwestern border province of Tak parasite prevalence is now estimated to be less than 1% by microscopy. Nonetheless, microscopy is insensitive at low-level parasitaemia. The objective of this study was to assess the current epidemiology of falciparum and vivax malaria in Tak using molecular methods to detect exposure to and infection with parasites; in particular, the prevalence of asymptomatic infections and infections with submicroscopic parasite levels.MethodsThree-hundred microlitres of whole blood from finger-prick were collected into capillary tubes from residents of a sentinel village and from patients at a malaria clinic. Pelleted cellular fractions were screened by quantitative PCR to determine parasite prevalence, while plasma was probed on a protein microarray displaying hundreds of P. falciparum and P. vivax proteins to obtain antibody response profiles in those individuals.ResultsOf 219 samples from the village, qPCR detected 25 (11.4%) Plasmodium sp. infections, of which 92% were asymptomatic and 100% were submicroscopic. Of 61 samples from the clinic patients, 27 (44.3%) were positive by qPCR, of which 25.9% had submicroscopic parasite levels. Cryptic mixed infections, misdiagnosed as single-species infections by microscopy, were found in 7 (25.9%) malaria patients. All sample donors, parasitaemic and non-parasitaemic alike, had serological evidence of parasite exposure, with 100% seropositivity to at least 54 antigens. Antigens significantly associated with asymptomatic infections were P. falciparum MSP2, DnaJ protein, putative E1E2 ATPase, and three others.ConclusionThese findings suggest that parasite prevalence is higher than currently estimated by local authorities based on the standard light microscopy. As transmission levels drop in Thailand, it may be necessary to employ higher throughput and sensitivity methods for parasite detection in the phase of malaria elimination.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0611-9) contains supplementary material, which is available to authorized users.

Complete Genome Sequence of Bovine Viral Diarrhea Virus 2 Japanese Reference and Vaccine Strain KZ-91CP.

In this study, we report the complete genome sequence of the bovine viral diarrhea virus 2 Japanese reference strain KZ-91CP. The complete genome comprises 12,654 nucleotides and one open reading frame with 4,020 amino acids. A 369-nucleotide-long insertion encoding the chaperone protein DnaJ is found in the nonstructural 2 (NS2) coding region.

Characterization of the cytopathic BVDV strains isolated from 13 mucosal disease cases arising in a cattle herd

Bovine viral diarrhea virus (BVDV) is a positive single stranded RNA virus belonging to the Pestivirus genus of the Flaviviridae family. BVDV has a wide host range that includes most ruminants. Noncytopathic (ncp) BVDV may establish lifelong persistent infections in calves following infection of the fetus between 40 and 120 days of gestation. Cytopathic (cp) BVDV strains arise from ncp strains via mutations. The most common cp mutations are insertions of RNA derived from either host or a duplication of viral sequences into the region of the genome coding for the NS2/3 protein. Superinfection of a persistently infected animal with a cp virus can give rise to mucosal disease, a condition that is invariably fatal. A herd of 136 bred 3-year old cows was studied. These cows gave birth to 41 PI animals of which 23 succumbed to mucosal disease. In this study, we characterized the ncp and cp viruses isolated from 13 of these animals. All viruses belonged to the BVDV type 2a genotype and were highly similar. All the cp viruses contained an insertion in the NS2/3 coding region consisting of the sequences derived from the transcript encoding a DnaJ protein named Jiv90. Comparison of the inserted DnaJ regions along with the flanking viral sequences in the insertion 3′ end of the 13 cp isolates revealed sequence identities ranging from 96% to 99% with common borders. This suggested that one animal likely developed a cp virus that then progressively spread to the other 12 animals. Interestingly, when the inserted mammalian gene replicated within viral genome, it showed conservation of the same conserved motifs between the different species, which may indicate a role for these motifs in the insertion function within the virus genome. This is the first characterization of multiple cp bovine viral diarrhea virus isolates that spread in a herd under natural conditions.

Overexpression of a tobacco J-domain protein enhances drought tolerance in transgenic Arabidopsis

DnaJ proteins constitute a DnaJ/Hsp40 family and are important regulators involved in diverse cellular functions. To date, the molecular mechanisms of DnaJ proteins involved in response to drought stress in plants are largely unknown. In this study, a putative DnaJ ortholog from Nicotiana tabacum (NtDnaJ1), which encodes a putative type-I J-protein, was isolated. The transcript levels of NtDnaJ1 were higher in aerial tissues and were markedly up-regulated by drought stress. Over-expression of NtDnaJ1 in Arabidopsis plants enhanced their tolerance to osmotic or drought stress. Quantitative determination of H2O2 accumulation has shown that H2O2 content increased in wild-type and transgenic seedlings under osmotic stress, but was significantly lower in both transgenic lines compared with the wild-type. Expression analysis of stress-responsive genes in NtDnaJ1-transgenic Arabidopsis revealed that there was significantly increased expression of genes involved in the ABA-dependent signaling pathway (AtRD20, AtRD22 and AtAREB2) and antioxidant genes (AtSOD1, AtSOD2, and AtCAT1). Collectively, these data demonstrate that NtDnaJ1 could be involved in drought stress response and its over-expression enhances drought tolerance possibly through regulating expression of stress-responsive genes. This study may facilitate our understandings of the biological roles of DnaJ protein-mediated abiotic stress in higher plants and accelerate genetic improvement of crop plants tolerant to environmental stresses.

Overexpression of tomato chloroplast-targeted DnaJ protein enhances tolerance to drought stress and resistance to Pseudomonas solanacearum in transgenic tobacco

DnaJ proteins as co-chaperones have critical functions in biotic and abiotic stress responses, but their biological functions remain largely uninvestigated. This study investigates the function of a tomato (Lycopersicon esculentum) chloroplast-targeted DnaJ protein (LeCDJ2) using transgenic tobacco. Quantitative real-time polymerase chain reaction analysis showed that LeCDJ2 expression was triggered by salicylic acid (SA), drought and pathogen attack. Ectopic expression of LeCDJ2 in transgenic tobacco reduced the accumulation of superoxide anion radical (O2−) and hydrogen peroxide (H2O2) under drought stress. Compared with Vec plants, the maximum photochemical efficiency of photosystem II (PSII) (Fv/Fm), net photosynthetic rate (Pn), and content of D1 protein were relatively higher in transgenic plants. The transgenic plants showes better growth, higher chlorophyll content, lower malondialdehyde (MDA) accumulation and relative electrolyte leakage (REL) under drought stress. In addition, overexpression of LeCDJ2 improved the resistance to the pathogen Pseudomonas solanacearum in transgenic tobacco. These results indicate that overexpression of a tomato chloroplast-targeted DnaJ gene enhances tolerance to drought stress and resistance to P. solanacearum in transgenic tobacco.