Homologous Overexpression Research Articles

Genome-Wide Characterization and Expression Analysis of Soybean TGA Transcription Factors Identified a Novel TGA Gene Involved in Drought and Salt Tolerance.

The TGA transcription factors, a subfamily of bZIP group D, play crucial roles in various biological processes, including the regulation of growth and development as well as responses to pathogens and abiotic stress. In this study, 27 TGA genes were identified in the soybean genome. The expression patterns of GmTGA genes showed that several GmTGA genes are differentially expressed under drought and salt stress conditions. Among them, GmTGA17 was strongly induced by both stress, which were verificated by the promoter-GUS fusion assay. GmTGA17 encodes a nuclear-localized protein with transcriptional activation activity. Heterologous and homologous overexpression of GmTGA17 enhanced tolerance to drought and salt stress in both transgeinc Arabidopsis plants and soybean hairy roots. However, RNAi hairy roots silenced for GmTGA17 exhibited an increased sensitivity to drought and salt stress. In response to drought or salt stress, transgenic Arabidopsis plants had an increased chlorophyll and proline contents, a higher ABA content, a decreased MDA content, a reduced water loss rate, and an altered expression of ABA- responsive marker genes compared with WT plants. In addition, transgenic Arabidopsis plants were more sensitive to ABA in stomatal closure. Similarly, measurement of physiological parameters showed an increase in chlorophyll and proline contents, with a decrease in MDA content in soybean seedlings with overexpression hairy roots after drought and salt stress treatments. The opposite results for each measurement were observed in RNAi lines. This study provides new insights for functional analysis of soybean TGA transcription factors in abiotic stress.

Genetic Modification of Mucor circinelloides to Construct Stearidonic Acid Producing Cell Factory.

Stearidonic acid (SDA; 18:4, n-3) is the delta 15-desaturase product of gamma linolenic acid (GLA; 18:3, n-6) and delta 6-desaturase product of alpha linolenic acid (ALA; 18:3, n-3). Construction of engineered oleaginous microbes have been attracting significant interest in producing SDA because of its nutritional value and pharmaceutical applications. Mucor circinelloides is a GLA producing filamentous fungus, which can be a useful tool to produce SDA. This study has, therefore, overexpressed the delta-15 desaturase (D15D) gene from Mortierella alpina in this fungus to construct a SDA-producing cell factory. To produce SDA in M. circinelloides, the homologous overexpression of D15D gene was analyzed. When the gene was overexpressed in M. circinelloides CBS 277.49, up to 5.0% SDA was accumulated in this strain. According to current knowledge, this is the first study describing the construction of a SDA-producing cell factory by overexpression of D15D gene in oleaginous fungus M. circinelloides. A new scope for further research has been established by this work to improve SDA production in this fungus, specifically in its high lipid-producing strain, WJ11.

Construction of DGLA producing cell factory by genetic modification of Mucor circinelloides

BackgroundDihomo-gamma linolenic acid (DGLA, 20:3, n-6) is the elongated product of Gamma linolenic acid (GLA, 18:3, n-6) catalyzed by the enzyme delta-6 elongase (D6E) or gamma linolenic acid elongase (GLELO). Construction of engineered oleaginous microbes have been attracting significant interest to produce DGLA because of its nutritional value and medicinal applications. Mucor circinelloides is a GLA producing filamentous fungus which can be a useful tool to produce DGLA. We have, therefore, overexpressed the D6E (GLELO) gene in this fungus to construct DGLA producing cell factory.ResultTo produce DGLA in M. circinelloides, homologous overexpression of D6E (GLELO) gene was analyzed. When the gene was overexpressed in M. circinelloides CBS277.49, up to 5.72% DGLA was produced in this strain.ConclusionTo our knowledge, this is the first report describing the overexpression of D6E (GLELO) gene in M. circinelloides to construct DGLA producing cell factory. A new scope for further research has been established by this work for improved production of DGLA in this fungus, specifically in its high lipid-producing strain, WJ11.

Cyclic nucleotides in archaea: Cyclic di-AMP in the archaeon Haloferax volcanii and its putative role.

The role of cyclic nucleotides as second messengers for intracellular signal transduction has been well described in bacteria. One recently discovered bacterial second messenger is cyclic di‐adenylate monophosphate (c‐di‐AMP), which has been demonstrated to be essential in bacteria. Compared to bacteria, significantly less is known about second messengers in archaea. This study presents the first evidence of in vivo presence of c‐di‐AMP in an archaeon. The model organism Haloferax volcanii was demonstrated to produce c‐di‐AMP. Its genome encodes one diadenylate cyclase (DacZ) which was shown to produce c‐di‐AMP in vitro. Similar to bacteria, the dacZ gene is essential and homologous overexpression of DacZ leads to cell death, suggesting the need for tight regulation of c‐di‐AMP levels. Such tight regulation often indicates the control of important regulatory processes. A central target of c‐di‐AMP signaling in bacteria is cellular osmohomeostasis. The results presented here suggest a comparable function in H. volcanii. A strain with decreased c‐di‐AMP levels exhibited an increased cell area in hypo‐salt medium, implying impaired osmoregulation. In summary, this study expands the field of research on c‐di‐AMP and its physiological function to archaea and indicates that osmoregulation is likely to be a common function of c‐di‐AMP in bacteria and archaea.

Homologous overexpression of hydrogenase and glycerol dehydrogenase in Clostridium pasteurianum to enhance hydrogen production from crude glycerol

This study reports engineering of a hypertransformable variant of C. pasteurianum for bioconversion of glycerol into hydrogen (H2). A functional glycerol-triggered hydrogen pathway was engineered based on two approaches: (1) increasing product yield by overexpression of immediate enzyme catalyzing H2 production, (2) increasing substrate uptake by overexpression of enzymes involved in glycerol utilization. The first strategy aimed at overexpression of hydA gene encoding hydrogenase, and the second one, through combination of overexpression of dhaD1 and dhaK genes encoding glycerol dehydrogenase and dihydroxyacetone kinase. These genetic manipulations resulted in two recombinant strains (hydA++/dhaD1K++) capable of producing 97% H2 (v/v), with yields of 1.1 mol H2/mol glycerol in hydA overexpressed strain, and 0.93 mol H2/mol glycerol in dhaD1K overexpressed strain, which was 1.5 fold higher than wild type. Among two strains, dhaD1K++ consumed more glycerol than hydA++ which proves that overexpression of glycerol enzymes has enhanced glycerol intake rate.

A pilot study on the effect of lactoferrin on Alzheimer’s disease pathological sequelae: Impact of the p-Akt/PTEN pathway

Alzheimer’s disease (AD) is one of the most common neurodegenerative diseases in which the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (PKB or Akt) pathway is deregulated in response to phosphatase and tensin homolog (PTEN) overexpression. Lactoferrin (LF), a multifunctional iron-binding glycoprotein, is involved in AD pathology; however, direct evidence of its impact upon AD remains unclear. To elucidate LF’s role in AD, the possible protective mechanism post-LF administration for 3 months was investigated in AD patients by observing changes in the p-Akt/PTEN pathway. AD patients showed decreased serum acetylcholine (ACh), serotonin (5-HT), antioxidant and anti-inflammatory markers, and decreased expression of Akt in peripheral blood lymphocytes (PBL), as well as PI3K, and p-Akt levels in PBL lysate; all these parameters were significantly improved after daily LF administration for 3 months. Similarly, elevated serum amyloid β (Aβ) 42, cholesterol, oxidative stress markers, IL-6, heat shock protein (HSP) 90, caspase-3, and p-tau, as well as increased expression of tau, MAPK1 and PTEN in AD patients, were significantly reduced upon LF intake. Improvement in the aforementioned AD surrogate markers post-LF treatment was reflected in enhanced cognitive function assessed by the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-Cognitive Subscale 11-item (ADAS-COG 11) questionnaires as clinical endpoints. These results provide a basis for a possible protective mechanism of LF in AD through its ability to alleviate the AD pathological cascade and cognitive decline via modulation of the p-Akt/PTEN pathway, which affects the key players of inflammation and oxidative stress that are involved in AD pathology.

Improved production of the NiFe-hydrogenase from Pyrococcus furiosus by increased expression of maturation genes.

The NADPH-dependent cytoplasmic [NiFe]-hydrogenase (SHI) from the hyperthermophile Pyrococcus furiosus, which grows optimally near 100°C, is extremely thermostable and has many in vitro applications, including cofactor generation and hydrogen production. In particular, SHI is used in a cell-free synthetic pathway that contains more than a dozen other enzymes and produces three times more hydrogen (12 H2/glucose) from sugars compared to cellular fermentations (4 H2/glucose). We previously reported homologous over-expression and rapid purification of an affinity-tagged (9x-His) version of SHI, which is a heterotetrameric enzyme. However, about 30% of the enzyme that was purified contained an inactive trimeric form of SHI lacking the catalytic [NiFe]-containing subunit. Herein, we constructed a strain of P. furiosus that contained a second set of the eight genes involved in the maturation of the catalytic subunit and insertion of the [NiFe]-site, along with a second set of the four genes encoding the SHI structural subunits. This resulted in a 40% higher yield of the purified affinity-tagged enzyme and the content of the inactive trimeric form decreased to 5% of the total protein. These results bode well for the future production of active SHI for both basic and applied purposes.

Homologous overexpression of NpDps2 and NpDps5 increases the tolerance for oxidative stress in the multicellular cyanobacterium Nostoc punctiforme.

The filamentous cyanobacterium Nostoc punctiforme has several oxidative stress-managing systems, including Dps proteins. Dps proteins belong to the ferritin superfamily and are involved in abiotic stress management in prokaryotes. Previously, we found that one of the five Dps proteins in N. punctiforme, NpDps2, was critical for H2O2 tolerance. Stress induced by high light intensities is aggravated in N. punctiforme strains deficient of either NpDps2, or the bacterioferritin-like NpDps5. Here, we have investigated the capacity of NpDps2 and NpDps5 to enhance stress tolerance by homologous overexpression of these two proteins in N. punctiforme. Both overexpression strains were found to tolerate twice as high concentrations of added H2O2 as the control strain, indicating that overexpression of either NpDps2 or NpDps5 will enhance the capacity for H2O2 tolerance. Under high light intensities, the overexpression of the two NpDps did not enhance the tolerance against general light-induced stress. However, overexpression of the heterocyst-specific NpDps5 in all cells of the filament led to a higher amount of chlorophyll-binding proteins per cell during diazotrophic growth. The OENpDps5 strain also showed an increased tolerance to ammonium-induced oxidative stress. Our results provide information of how Dps proteins may be utilised for engineering of cyanobacteria with enhanced stress tolerance.

Improved Polysaccharide Production by Homologous Co-overexpression of Phosphoglucomutase and UDP Glucose Pyrophosphorylase Genes in the Mushroom Coprinopsis cinerea.

Coprinopsis polysaccharides exhibit hypoglycemic and antioxidant activities. In this report, increases in polysaccharide production by homologous co-overexpression or individual homologous overexpression of phosphoglucomutase and UDP glucose pyrophosphorylase gene in Coprinopsis cinerea, which participate in polysaccharide biosynthesis. The transcription levels of the target genes were upregulated significantly in the oePGM-UGP strain when compared with the oePGM or oeUGP strain. The maximum intracellular polysaccharide content obtained in the oePGM-UGP strain was 1.49-fold higher than that of the WT strain, whereas a slight improvement in polysaccharide production was obtained in the oePGM and oeUGP strains. Extracellular polysaccharide production was enhanced by 75% in the oePGM-UGP strain when compared with that of the WT strain, whereas improvements of 30% and 16% were observed for the oePGM and oeUGP strains, respectively. These results show that multiple interventions in polysaccharide biosynthesis pathways of Basidiomycetes might improve polysaccharide yields when compared with that of single interventions.

Cdc20/p55 mediates the resistance to docetaxel in castration-resistant prostate cancer in a Bim-dependent manner.

At least to date, no effective treatment for advanced castration-resistant prostate cancer (CRPC) has been established. Recent studies indicated that cell division cycle 20 homolog (Cdc20) overexpression is associated with poor prognosis in patients with castration-resistant prostate cancer. However, the mechanism of Cdc20 in the development of docetaxel resistance in CRPC remains elusive. In this study, the transcription of Cdc20 was confirmed in three independent CRPC cell lines derived from different tissues, including LNCaP, PC3, and DU145. Docetaxel resistant (DR) cell lines were generated within the background of DU145 and PC3. The protein levels of Cdc20 and the biological phenotype were detected in both wild-type and DR cell lines. To further explore the mechanism of Cdc20 overexpression, stable cell lines with Cdc20 or Bcl-2 interacting mediator of cell death (Bim) deprivation were generated and examined for biological parameters. In addition, a specific Cdc20 inhibitor was used in DR cell lines to explore the potential solution for docetaxel resistant CRPC. Here, we identified Cdc20 is overexpressed in docetaxel resistant CRPC cell lines, including LNCaP, PC3, and DU145. We also reported that DR cell lines, which mimic the recurrent prostate cancer cells after docetaxel treatment, have higher levels of Cdc20 protein compared with the CRPC cell lines. Interestingly, the protein levels of Bim, an E3 ligase substrate of Cdc20, were decreased in DR cell lines compared with the wild-type, while the mRNA levels were similar. More importantly, in DR cell lines, the biological phenotype induced by Cdc20 deletion could be significantly reversed by the additional knockdown of Bim. As a result, docetaxel resistant prostate cancer cells treated with the pharmacological Cdc20 inhibitor became sensitive to docetaxel treatment. In conclusion, our data collectively demonstrated that Cdc20 overexpression facilitates the docetaxel resistant of the CRPC cell lines in a Bim-dependent manner. Furthermore, additionally targeting Cdc20 might be a promising solution for the treatment of the CRPC with docetaxel resistance.

Engineering Yarrowia lipolytica to Simultaneously Produce Lipase and Single Cell Protein from Agro-industrial Wastes for Feed

Lipases are scarcely exploited as feed enzymes in hydrolysis of lipids for increasing energy supply and improving nutrient use efficiency. In this work, we performed homologous overexpression, in vitro characterization and in vivo assessment of a lipase from the yeast Yarrowia lipolytica for feed purpose. Simultaneously, a large amount of yeast cell biomass was produced, for use as single cell protein, a potential protein-rich feed resource. Three kinds of low cost agro-industrial wastes were tested as substrates for simultaneous production of lipase and single cell protein (SCP) as feed additives: sugarcane molasses, waste cooking oil and crude glycerol from biodiesel production. Sugarcane molasses appeared as the most effective cheap medium, allowing production of 16420 U/ml of lipase and 151.2 g/L of single cell protein at 10 liter fermentation scale. In vitro characterization by mimicking a gastro-intestinal environment and determination of essential amino acids of the SCP, and in vivo oral feeding test on fish all revealed that lipase, SCP and their combination were excellent feed additives. Such simultaneous production of this lipase and SCP could address two main concerns of feed industry, poor utilization of lipid and shortage of protein resource at the same time.

Characterization of Two VAO-Type Flavoprotein Oxidases from Myceliophthora thermophila.

The VAO flavoprotein family consists mostly of oxidoreductases harboring a covalently linked flavin cofactor. The linkage can be either monocovalent at position 8 with a histidine or tyrosine or bicovalent at position 8 with a histidine and at position 6 with a cysteine. Bicovalently bound flavoproteins show a preference for bulkier substrates such as oligosaccharides or secondary metabolites. The genome of the thermophilic fungus Myceliophthora thermophila C1 was found to be rich in genes encoding putative covalent VAO-type flavoproteins. Enzymes from this fungus have the advantage of being rather thermostable and homologous overexpression in M. thermophila C1 is feasible. Recently we discovered a new and VAO-type carbohydrate oxidase from this fungus: xylooligosaccharide oxidase. In this study, two other putative VAO-type oxidases, protein sequence XP_003663615 (MtVAO615) and XP_003665713 (MtVAO713), were expressed in M. thermophila C1, purified and characterized. Enzyme MtVAO615 was found to contain a bicovalently bound FAD, while enzyme MtVAO713 contained a monocovalent histidyl-bound FAD. The crystal structures of both proteins were obtained which revealed atypical active site architectures. It could be experimentally verified that both proteins, when reduced, rapidly react with molecular oxygen, a hallmark of flavoprotein oxidases. A large panel of alcohols, including carbohydrates, steroids and secondary alcohols were tested as potential substrates. For enzyme MtVAO713 low oxidase activity was discovered towards ricinoleic acid.

The Copper Homeostasis Transcription Factor CopR Is Involved in H2O2 Stress in Lactobacillus plantarum CAUH2.

Transcriptional factors (TFs) play important roles in the responses to oxidative, acid, and other environmental stresses in Gram-positive bacteria, but the regulatory mechanism of TFs involved in oxidative stress remains unknown in lactic acid bacteria. In the present work, homologous overexpression strains with 43 TFs were constructed in the Lactobacillus plantarum CAUH2 parent strain. The strain overexpressing CopR displayed the highest sensitivity and a 110-fold decrease in survival rate under H2O2 challenge. The importance of CopR in the response to H2O2 stress was further confirmed by a 10.8-fold increase in the survival of a copR insertion mutant. In silico analysis of the genes flanking copR revealed putative CopR-binding “cop box” sequences in the promoter region of the adjacent gene copB encoding a Cu2+-exporting ATPase. Electrophoretic mobility shift assay (EMSA) analysis demonstrated the specific binding of CopR with copB in vitro, suggesting copB is a target gene of CopR in L. plantarum. The role of CopB involved in oxidative stress was verified by the significantly decreased survival in the copB mutant. Furthermore, a growth defect in copper-containing medium demonstrated that CopB functions as an export ATPase for copper ions. Furthermore, EMSAs revealed that CopR functions as a regulator that negatively regulates copB gene and Cu2+ serves as inducer of CopR to activate the expression of CopB in response to H2O2 stress in L. plantarum CAUH2. Our findings indicated that CopR plays an important role in enhancing oxidative resistance by regulating copB to modulate copper homeostasis.

Improved \u03b3-linolenic acid production in Mucor circinelloides by homologous overexpressing of delta-12 and delta-6 desaturases

Backgroundγ-Linolenic acid (GLA) is important because of its nutritional value and medicinal applications. Although the biosynthetic pathways of some plant and microbial GLA have been deciphered, current understanding of the correlation between desaturases and GLA synthesis in oleaginous fungi is incomplete. In previous work, we found that a large amount of oleic acid (OA) had not been converted to linoleic acid (LA) or GLA in Mucor circinelloides CBS 277.49, which may be due to inadequate activities of the delta-12 or delta-6 desaturases, and thus leading to the accumulation of OA and LA. Thus, it is necessary to explore the main contributing factor during the process of GLA biosynthesis in M. circinelloides.ResultsTo enhance GLA production in M. circinelloides, homologous overexpression of delta-12 and two delta-6 desaturases (named delta-6-1 and delta-6-2, respectively) were analyzed. When delta-6 desaturase were overexpressed in M. circinelloides, up to 43% GLA was produced in the total fatty acids, and the yield of GLA reached 180 mg/l, which were, respectively, 38 and 33% higher than the control strain.ConclusionThese findings revealed that delta-6 desaturase (especially for delta-6-1 desaturase) plays an important role in GLA synthesis by M. circinelloides. The strain overexpressing delta-6-1 desaturase may have potential application in microbial GLA production.

Modification of Different Pulps by Homologous Overexpression Alkali-Tolerant Endoglucanase in Bacillus subtilis Y106

Cellulase (mainly endoglucanase, EG) has been used in pulp modification for improving paper quality through environmentally friendly process. But low activity in alkaline pH and high filter paper activity (FPA) were still obstacles for extending the cellulase application in papermaking industry. In the study, an alkali-tolerant EG gene of Bacillus subtilis Y106 was homologous over-expressed for obtaining suitable enzyme used in pulp modification. The engineering strain could produce the crude enzyme with more alkali-tolerant EG and little PFA. Potential of the crude enzyme in modification of different pulps were investigated. It was found that the enzyme could be used for improving drainage and strength properties of pulps from softwood, hardwood and non-wood materials, especially non-wood pulp such as wheat straw pulp. The underlying mechanisms of pulp modification and different effects on various types of pulps by the EG treatment were also discussed by studying the change in fibers characteristics and fiber bonding.

Metabolic engineering of Klebsiella pneumoniae J2B for the production of 1,3-propanediol from glucose

The production of 1,3-propanediol (1,3-PDO) from glucose was investigated using Klebsiella pneumoniae J2B, which converts glycerol to 1,3-PDO and synthesize an essential coenzyme B12. In order to connect the glycolytic pathway with the pathway of 1,3-PDO synthesis from glycerol, i.e., to directly produce diol from glucose, glycerol-3-phosphate dehydrogenase and glycerol-3-phosphate phosphatase from Saccharomyces cerevisiae were overexpressed. Additionally, the effect of expression levels and the use of isoforms of these two enzymes on glycerol and 1,3-PDO production were studied. Furthermore, to prevent loss of produced glycerol, the glycerol oxidation pathways were disrupted. Finally, the conversion rate of glycerol to 1,3-PDO was increased via homologous overexpression of glycerol dehydratase and 1,3-PDO oxidoreductase. The resultant strain successfully produced 1,3-PDO from glucose at a yield of 0.27mol/mol along with glycerol at 0.52mol/mol. Improvement of the engineered K. pneumoniae J2B to further increase conversion of glycerol to 1,3-PDO is discussed.

Heat shock protein 104 (Hsp104)-mediated curing of [PSI+] yeast prions depends on both [PSI+] conformation and the properties of the Hsp104 homologs

Prions arise from proteins that have two possible conformations: properly folded and non-infectious or misfolded and infectious. The [PSI+] yeast prion, which is the misfolded and self-propagating form of the translation termination factor eRF3 (Sup35), can be cured of its infectious conformation by overexpression of Hsp104, which helps dissolve the prion seeds. This dissolution depends on the trimming activity of Hsp104, which reduces the size of the prion seeds without increasing their number. To further understand the relationship between trimming and curing, trimming was followed by measuring the loss of GFP-labeled Sup35 foci from both strong and weak [PSI+] variants; the former variant has more seeds and less soluble Sup35 than the latter. Overexpression of Saccharomyces cerevisiae Hsp104 (Sc-Hsp104) trimmed the weak [PSI+] variants much faster than the strong variants and cured the weak variants an order of magnitude faster than the strong variants. Overexpression of the fungal Hsp104 homologs from Schizosaccharomyces pombe (Sp-Hsp104) or Candida albicans (Ca-Hsp104) also trimmed and cured the weak variants, but interestingly, it neither trimmed nor cured the strong variants. These results show that, because Sc-Hsp104 has greater trimming activity than either Ca-Hsp104 or Sp-Hsp104, it cures both the weak and strong variants, whereas Ca-Hsp104 and Sp-Hsp104 only cure the weak variants. Therefore, curing by Hsp104 overexpression depends on both the trimming ability of the fungal Hsp104 homolog and the strength of the [PSI+] variant: the greater the trimming activity of the Hsp104 homolog and the weaker the variant, the greater the curing.

Ectopic expression of two AREB/ABF orthologs increases drought tolerance in cotton (Gossypium hirsutum).

Plants have evolved complex molecular, cellular and physiological mechanisms to respond to environmental stressors. Because of the inherent complexity of this response, genetic manipulation to substantially improve water deficit tolerance, particularly in agricultural crops, has been largely unsuccessful, as the improvements are frequently accompanied by slower growth and delayed reproduction. Here, we ectopically express two abiotic stress-responsive bZIP AREB/ABF transcription factor orthologs, Arabidopsis ABF3 and Gossypium hirsutum ABF2D, in G. hirsutum, to compare the effects of exogenous and endogenous AREB/ABF transgene overexpression on dehydration resilience. Our results show that ectopic expression of each of these orthologs increases dehydration resilience, although these increases are accompanied by slower growth. These phenotypic effects are proportional to the ectopic expression level in the GhABF2D transgenic plants, while the phenotypes of all of the AtABF3 transgenic plants are similar, largely independent of ectopic expression level, possibly indicating differential post-transcriptional regulation of these transgenes. Our results indicate that overexpression of exogenous and endogenous ABF homologs in G. hirsutum substantially increases drought resilience, primarily through stomatal regulation, negatively impacting transpiration and photosynthetic productivity.

Candida guilliermondii as a potential biocatalyst for the production of long-chain α,ω-dicarboxylic acids.

To explore Candida guilliermondii for the production of long-chain dicarboxylic acids (DCA), we performed metabolic pathway engineering aiming to prevent DCA consumption during β-oxidation, but also to increase its production via the ω-oxidation pathway. We identified the major β- and ω-oxidation pathway genes in C. guilliermondii and performed first steps in the strain improvement. A double pox disruption mutant was created that slowed growth with oleic acid but showed accelerated DCA degradation. Increase in DCA production was achieved by homologous overexpression of a plasmid borne cytochrome P450 monooxygenase gene. C. guilliermondii is a promising biocatalyst for DCA production but further insight into its fatty acid metabolism is necessary.

Overexpression of an Arabidopsis heterogeneous nuclear ribonucleoprotein gene, AtRNP1, affects plant growth and reduces plant tolerance to drought and salt stresses

Heterogeneous nuclear ribonucleoproteins (hnRNPs) participate in diverse regulations of plant growth and environmental stress responses. In this work, an Arabidopsis hnRNP of unknown function, AtRNP1, was investigated. We found that AtRNP1 gene is highly expressed in rosette and cauline leaves, and slightly induced under drought, salt, osmotic and ABA stresses. AtRNP1 protein is localized to both the nucleus and cytoplasm. We performed homologous overexpression of AtRNP1 and found that the transgenic plants showed shortened root length and plant height, and accelerated flowering. In addition, the transgenic plants also showed reduced tolerance to drought, salt, osmotic and ABA stresses. Further studies revealed that under both normal and stress conditions, the proline contents in the transgenic plants are markedly decreased, associated with reduced expression levels of a proline synthase gene and several stress-responsive genes. These results suggested that the overexpression of AtRNP1 negatively affects plant growth and abiotic stress tolerance.