Machine learning-based algorithm identifies key mitochondria-related genes in non-alcoholic steatohepatitis.

BACKGROUND: Evidence suggests that hepatocyte mitochondrial dysfunction leads to abnormal lipid metabolism, redox imbalance, and programmed cell death, driving the onset and progression of non-alcoholic steatohepatitis (NASH). Identifying hub mitochondrial genes linked to NASH may unveil potential therapeutic targets. METHODS: Mitochondrial hub genes implicated in NASH were identified via analysis using 134 algorithms. RESULTS: The Random Forest algorithm (RF), the most effective among the 134 algorithms, identified three genes: Aldo-keto reductase family 1 member B10 (AKR1B10), thymidylate synthase (TYMS), and triggering receptor expressed in myeloid cell 2 (TREM2). They were upregulated and positively associated with genes promoting inflammation, genes involved in lipid synthesis, fibrosis, and nonalcoholic steatohepatitis activity scores in patients with NASH. Moreover, using these three genes, patients with NASH were accurately categorized into cluster 1, exhibiting heightened disease severity, and cluster 2, distinguished by milder disease activity. CONCLUSION: These three genes are pivotal mitochondrial genes implicated in NASH progression.

A novel aldo-keto reductase gene, OsAKR1, from rice confers higher tolerance to cadmium stress in rice by an in vivo reactive aldehyde detoxification.

Elevated levels of cadmium (Cd) have the ability to impede plant development. Aldo-keto reductases (AKRs) have been demonstrated in a number of plant species to improve tolerance to a variety of abiotic stresses by scavenging cytotoxic aldehydes; however, only a few AKRs have been identified to improve Cd tolerance. The OsAKR1 gene was extracted and identified from rice here. After being exposed to Cd, the expression of OsAKR1 dramatically rose in both roots and shoots, although more pronounced in roots. According to a subcellular localization experiment, the nucleus and cytoplasm are where OsAKR1 is primarily found. Mutants lacking OsAKR1 exhibited Cd sensitive phenotype than that of the wild-type (WT) Nipponbare (Nip), and osakr1 mutants exhibited reduced capacity to scavenge methylglyoxal (MG). Furthermore, osakr1 mutants exhibited considerably greater hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels, and increased catalase (CAT) activity in comparison to Nip. The expression of three isomeric forms of CAT was found to be considerably elevated in osakr1 mutants during Cd stress, as demonstrated by quantitative real-time PCR analysis, when compared to Nip. These results imply that OsAKR1 controlled rice's ability to withstand Cd by scavenging harmful aldehydes and turning on the reactive oxygen species (ROS) scavenging mechanism.

Computer-aided design to enhance the stability of aldo-keto reductase KdAKR.

The aldo-keto reductase (AKR) KdAKR from Kluyvermyces dobzhanskii can reduce t-butyl 6-chloro-(5S)-hydroxy-3-oxohexanoate ((5S)-CHOH) to t-butyl 6-chloro-(3R,5S)-dihydroxyhexanoate ((3R,5S)-CDHH), which is the key chiral intermediate of rosuvastatin. Herein, a computer-aided design that combined the use of PROSS platform and consensus design was employed to improve the stability of a previously constructed mutant KdAKRM6 . Experimental verification revealed that S196C, T232A, V264I and V45L produced improved thermostability and activity. The "best" mutant KdAKRM10 (KdAKRM6 -S196C/T232A/V264I/V45L) was constructed by combining the four beneficial mutations, which displayed enhanced thermostability. Its T50 15 and Tm values were increased by 10.2 and 10.0°C, respectively, and half-life (t1/2 ) at 40°C was increased by 17.6 h. Additionally, KdAKRM10 demonstrated improved resistance to organic solvents compared to that of KdAKRM6 . Structural analysis revealed that the increased number of hydrogen bonds and stabilized hydrophobic core contributed to the rigidity of KdAKRM10 , thus improving its stability. The results validated the feasibility of the computer-aided design strategy in improving the stability of AKRs.

A three-level regulatory mechanism of the aldo-keto reductase subfamily AKR12D.

Modulation of protein function through allosteric regulation is central in biology, but biomacromolecular systems involving multiple subunits and ligands may exhibit complex regulatory mechanisms at different levels, which remain poorly understood. Here, we discover an aldo-keto reductase termed AKRtyl and present its three-level regulatory mechanism. Specifically, by combining steady-state and transient kinetics, X-ray crystallography and molecular dynamics simulation, we demonstrate that AKRtyl exhibits a positive synergy mediated by an unusual Monod-Wyman-Changeux (MWC) paradigm of allosteric regulation at low concentrations of the cofactor NADPH, but an inhibitory effect at high concentrations is observed. While the substrate tylosin binds at a remote allosteric site with positive cooperativity. We further reveal that these regulatory mechanisms are conserved in AKR12D subfamily, and that substrate cooperativity is common in AKRs across three kingdoms of life. This work provides an intriguing example for understanding complex allosteric regulatory networks.

Multi-strategy orthogonal enhancement and analysis of aldo-keto reductase thermal stability.

Given their outstanding efficiency and selectivity, enzymes are integral in various domains such as drug synthesis, the food industry, and environmental management. However, the inherent instability of natural enzymes limits their widespread industrial application. In this study, we underscore the efficacy of enhancing protein thermal stability through comprehensive protein design strategies, encompassing elements such as the free energy of protein folding, internal forces within proteins, and the overall structural design. We also demonstrate the efficiency and precision of combinatorial screening in the thermal stability design of aldo-keto reductase (AKR7-2-1). In our research, three single-point mutations and five combinatorial mutations were strategically introduced into AKR7-2-1, using multiple computational techniques. Notably, the E12I/S235I mutant showed a significant increase of 25.4 °C in its melting temperature (Tm). Furthermore, the optimal mutant, E12V/S235I, maintained 80 % of its activity while realizing a 16.8 °C elevation in Tm. Remarkably, its half-life at 50 °C was increased to twenty times that of the wild type. Structural analysis indicates that this enhanced thermal stability primarily arises from reduced oscillation in the loop region and increased internal hydrogen bonding. The promising results achieved with AKR7-2-1 demonstrate that our strategy could serve as a valuable reference for enhancing the thermal stability of other industrial enzymes.

Aldo-keto reductase-7A2 protects against atorvastatin-induced hepatotoxicity via Nrf2 activation.

Atorvastatin (ATO), as a cholesterol-lowering drug, was the world's best-selling drug in the early 2000s. However, ATO overdose-induced liver or muscle injury is a threat to many patients, which restricts its application. Previous studies suggest that ATO overdose is accompanied with ROS accumulation and increased lipid peroxidation, which are the leading causes of ATO-induced liver damage. This study is, therefore, carried out to investigate the roles of anti-oxidant pathways and enzymes in protection against ATO-induced hepatotoxicity. Here we show that in ATO-challenged HepG2 cells, the expression levels of transcription factor NFE2L2/Nrf2 (nuclear factor erythroid 2 p45-related factor 2) are significantly upregulated. When Nrf2 is pharmacologically inhibited or genetically inactivated, ATO-induced cytotoxicity is significantly aggravated. Aldo-keto reductase-7A (AKR7A) enzymes, transcriptionally regulated by Nrf2, are important for bioactivation and biodetoxification. Here, we reveal that in response to ATO exposure, mRNA levels of human AKR7A2 are significantly upregulated in HepG2 cells. Furthermore, knockdown of AKR7A2 exacerbates ATO-induced hepatotoxicity, suggesting that AKR7A2 is essential for cellular adaptive response to ATO-induced cell damage. In addition, overexpression of AKR7A2 in HepG2 cells can significantly mitigate ATO-induced cytotoxicity and this process is Nrf2-dependent. Taken together, these findings indicate that Nrf2-mediated AKR7A2 is responsive to high concentrations of ATO and contributes to protection against ATO-induced hepatotoxicity, making it a good candidate for mitigating ATO-induced side effects.

Self-cascade deoxynivalenol detoxification by an artificial enzyme with bifunctions of dehydrogenase and aldo/keto reductase from genome mining.

Due to the severe health risks for human and animal caused by the intake of toxic deoxynivalenol (DON) derived from Fusarium species, elimination DON in food and feed has been initiated as a critical issue. Enzymatic cascade catalysis by dehydrogenase and aldo-keto reductase represents a fascinating strategy for DON detoxification. Here, one quinone-dpendent alcohol dehydrogenase DADH oxidized DON into less-toxic 3-keto-DON and NADPH-dependent aldo-keto reductase AKR13B3 reduced 3-keto-DON into relatively non-toxic 3-epi-DON were identified from Devosia strain A6-243, indicating that degradation of DON on C3 are two-step sequential cascade processes. To establish the bifunctions, fusion enzyme linking DADH and AKR13B3 was successfully assembled to promote one-step DON degradations with accelerated specific activity and efficiency, resulting 93.29 % of DON removal rate in wheat sample. Three-dimensional simulation analysis revealed that the bifunctional enzyme forms an artificial intramolecular channel to minimize the distance of intermediate from DADH to AKR13B3 for two-step enzymatic reactions, and thereby accelerates this enzymatic process. As the first report of directing single step DON detoxification by an interesting bifunctional artificial enzyme, this work revealed a facile and eco-friendly approach to detoxify DON with application potential and gave valuable insights into execute other mycotoxin detoxification for ensuring food safety.

Aldo-keto reductase 1C2 (AKR1C2) as the second gene associated to non-syndromic primary lipedema: investigating activating mutation or overexpression as causative factors.

OBJECTIVE: Lipedema is a debilitating chronic condition predominantly affecting women, characterized by the abnormal accumulation of fat in a symmetrical, bilateral pattern in the extremities, often coinciding with hormonal imbalances. PATIENTS AND METHODS: Despite the conjectured role of sex hormones in its etiology, a definitive link has remained elusive. This study explores the case of a patient possessing a mutation deletion within the C-terminal region of Aldo-keto reductases Member C2 (AKR1C2), Ser320PheTer2, that could lead to heightened enzyme activity. A cohort of 19 additional lipedema patients and 2 additional affected family members14 were enrolled in this study. The two additional affected family members are relatives of the patient with the AKR1C1 L213Q variant, which is included in the 19 cohorts and described in literature. RESULTS: Our investigation revealed that AKR1C2 was overexpressed, as quantified by qPCR, in 5 out of 21 (24%) lipedema patients who did not possess mutations in the AKR1C2 gene. Collectively, these findings implicate AKR1C2 in the pathogenesis of lipedema, substantiating its causative role. CONCLUSIONS: This study demonstrates that the activating mutation in the enzyme or its overexpression is a causative factor in the development of lipedema. Further exploration and replication in diverse populations will bolster our understanding of this significant connection.

Semi-rational engineering an aldo-keto reductase for stereocomplementary reduction of α-keto amide compounds.

Enantio-pure α-hydroxy amides are valuable intermediates for the synthesis of chiral pharmaceuticals. The asymmetric reduction of α-keto amides to generate chiral α-hydroxy amides is a difficult and challenging task in biocatalysis. In this study, iolS, an aldo-keto reductase from Bacillus subtilis 168 was exhibited as a potential biocatalyst, which could catalyze the reduction of diaryl α-keto amide such as 2-oxo-N, 2-diphenyl-acetamide (ONDPA) with moderate S-selectivity (76.1%, ee) and 60.5% conversion. Through semi-rational engineering, two stereocomplementary variants (I57F/F126L and N21A/F126A) were obtained with ee value of 97.6% (S) and 99.9% (R) toward ONDPA (1a), respectively, delivering chiral α-hydroxy amide with > 98% conversions. Moreover, the excellent S- and R-preference variants displayed improved stereoselectivities toward the other α-keto amide compounds. Molecular dynamic and docking analysis revealed that the two key residues at 21 and 126 were identified as the "switch", which specifically controlled the stereopreference of iolS by regulating the shape of substrate binding pocket as well as the substrate orientation. Our results offer an effective strategy to obtain α-hydroxy amides with high optical purity and provide structural insights into altering the stereoselectivity of AKRs.

Identification and functional characterization of a novel aldo-keto reductase from Aloe vera.

MAIN CONCLUSION: The present investigation profoundly asserted the catalytic potential of plant-based aldo-ketoreductase, postulating its role in polyketide biosynthesis and providing new insights for tailored biosynthesis of vital plant polyketides for therapeutics. Plants hold great potential as a future source of innovative biocatalysts, expanding the possibilities within chemical reactions and generating a variety of benefits. The aldo-keto reductase (AKR) superfamily includes a huge collection of NAD(P)H-dependent oxidoreductases that carry out a variety of redox reactions essential for biosynthesis, detoxification, and intermediary metabolism. The present study involved the isolation, cloning, and purification of a novel aldo-ketoreductase (AvAKR) from the leaves of Aloe vera (Aloe barbadensis Miller) by heterologous gene expression in Escherichia coli based on the unigene sequences of putative ketoreductase and cDNA library screening by oligonucleotide hybridization. The in-silico structural analysis, phylogenetic relationship, and molecular modeling were outranged to approach the novelty of the sequence. Additionally, agroinfiltration of the candidate gene tagged with a green fluorescent protein (GFP) was employed for transient expression in the Nicotiana benthamiana to evaluate the sub-cellular localization of the candidate gene. The AvAKR preferred cytoplasmic localization and shared similarities with the known plant AKRs, keeping the majority of the conserved active-site residues in the AKR superfamily enzymes. The enzyme facilitated the NADPH-dependent reduction of various carbonyl substrates, including benzaldehyde and sugars, proclaiming a broad spectrum range. Our study successfully isolated and characterized a novel aldo-ketoreductase (AvAKR) from Aloe vera, highlighting its versatile NADPH-dependent carbonyl reduction proficiency therewith showcasing its potential as a versatile biocatalyst in diverse redox reactions.

Aldo keto-reductase family 1C members 1 through 4 recombinant enzyme purification and enzyme assay.

Aldo-keto reductase family 1C (AKR1C) members transform steroids via their 3-, 17-, and 20-ketosteroid reductase activities. The biochemical study of these enzymes can help to inform their roles in hormone-dependent diseases and develop therapeutic inhibitors. This work describes a protocol to purify AKR1C1-4 members from a bacterial expression system using two chromatography steps. It also describes the basis of discontinuous assays to measure steroid conversion.

Aldo-keto Reductase 1B10 Restrains Cell Migration, Invasion, and Adhesion of Gastric Cancer via Regulating Integrin Subunit Alpha 5.

BACKGROUND/AIMS: Gastric cancer is a prevalent malignancy with unfavorable prognosis partially resulting from its high metastasis rate. Clarifying the molecular mechanism of gastric cancer occurrence and progression for improvement of therapeutic efficacy and prognosis is needed. The study tended to delineate the role and regulatory mechanism of aldo-keto reductase 1B10 (AKR1B10) in gastric cancer progression. MATERIALS AND METHODS: The relationship of AKR1B10 expression with survival rate in gastric cancer was analyzed through Kaplan-Meier analysis. The mRNA levels of AKR1B10 and integrin subunit alpha 5 (ITGA5) in gastric cancer tissues and cell lines were measured by real-time quantitative polymerase chain reaction. Protein levels of AKR1B10 and integrin subunit alpha 5 were assayed via western blot. The molecular relationship between AKR1B10 and ITGA5 was analyzed by co-immunoprecipitation assay. Cell viability was assayed through Cell Counting Kit-8, invasion and migration of tumor cells was assessed through wound healing and transwell assays. Transwell assay was utilized to detect invasion. The adhesion of gastric cancer cells was detected using cell adhesion assays. RESULTS: The results unveiled that integrin subunit alpha 5 was upregulated, while AKR1B10 was downregulated in gastric cancer tissues and cells. Overexpressing AKR1B10 hindered gastric cancer cell proliferation, migration, invasion and adhesion. It was striking that we certified the inhibitory effect of AKR1B10 on integrin subunit alpha 5 expression and their (AKR1B10 and ITGA5)) negative relationship via bioinformatics method, real-time quantitative polymerase chain reaction, and co-immunoprecipitation assays. Via rescue experiments, it was concluded that AKR1B10 served as tumor suppressor potentially by ITGA5 expression in gastric cancer. CONCLUSION: Our results indicated that AKR1B10 inhibited migration, invasion, and adhesion of gastric cancer cells via modulation of ITGA5.

Quantitative Analysis of mRNA and Protein Expression Levels of Aldo-Keto Reductase and Short-Chain Dehydrogenase/Reductase Isoforms in the Human Intestine.

Enzymes catalyzing the reduction reaction of xenobiotics are mainly members of the aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase (SDR) superfamilies. The intestine, together with the liver, is responsible for first-pass effects and is an organ that determines the bioavailability of orally administered drugs. In this study, we evaluated the mRNA and protein expression levels of 12 AKR isoforms (AKR1A1, AKR1B1, AKR1B10, AKR1B15, AKR1C1, AKR1C2, AKR1C3, AKR1C4, AKR1D1, AKR1E2, AKR7A2, and AKR7A3) and 7 SDR isoforms (CBR1, CBR3, CBR4, DCXR, DHRS4, HSD11B1, and HSD17B12) in each region of the human intestine using next-generation sequencing and data-independent acquisition proteomics. At both the mRNA and protein levels, most AKR isoforms were highly expressed in the upper regions of the intestine, namely the duodenum and jejunum, and then declined toward the rectum. Among the members in the SDR superfamily, CBR1 and DHRS4 were highly expressed in the upper regions, whereas the expression levels of the other isoforms were almost uniform in all regions. Significant positive correlations between mRNA and protein levels were observed in AKR1A1, AKR1B1, AKR1B10, AKR1C3, AKR7A2, AKR7A3, CBR1, and CBR3. The mRNA level of AKR1B10 was highest, followed by AKR7A3 and CBR1, each accounting for more than 10% of the sum of all AKR and SDR levels in the small intestine. This expression profile in the human intestine was greatly different from that in the human liver, where AKR1C isoforms are predominantly expressed. SIGNIFICANCE STATEMENT: In this study comprehensively determined the mRNA and protein expression profiles of aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase isoforms involved in xenobiotic metabolism in the human intestine and found that most of them are highly expressed in the upper region, where AKR1B10, AKR7A3, and CBR1 are predominantly expressed. Since the intestine is significantly involved in the metabolism of orally administered drugs, the information provided here is valuable for pharmacokinetic studies in drug development.

Structural-guided design to improve the catalytic performance of aldo-keto reductase KdAKR.

Aldo-keto reductases (AKRs) are important biocatalysts that can be used to synthesize chiral pharmaceutical alcohols. In this study, the catalytic activity and stereoselectivity of a NADPH-dependent AKR from Kluyveromyces dobzhanskii (KdAKR) toward t-butyl 6-chloro (5S)-hydroxy-3-oxohexanoate ((5S)-CHOH) were improved by mutating its residues in the loop regions around the substrate-binding pocket. And the thermostability of KdAKR was improved by a consensus sequence method targeted on the flexible regions. The best mutant M6 (Y28A/L58I/I63L/G223P/Y296W/W297H) exhibited a 67-fold higher catalytic efficiency compared to the wild-type (WT) KdAKR, and improved R-selectivity toward (5S)-CHOH (dep value from 47.6% to >99.5%). Moreover, M6 exhibited a 6.3-fold increase in half-life (t1/2 ) at 40°C compared to WT. Under the optimal conditions, M6 completely converted 200 g/L (5S)-CHOH to diastereomeric pure t-butyl 6-chloro-(3R, 5S)-dihydroxyhexanoate ((3R, 5S)-CDHH) within 8.0 h, with a space-time yield of 300.7 g/L/day. Our results deepen the understandings of the structure-function relationship of AKRs, providing a certain guidance for the modification of other AKRs.

Function, drug resistance and prognostic effect of AKR1C2 in human cancer.

Aldo-keto reductases (ARKs), a group of reductases that rely on nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) to catalyze carbonyl, are widely found in various organisms, which play an important role in the physiological and pathological processes of human. Aldo-keto reductase family 1 member C2 (AKR1C2) as a member of the human ARKs family, can regulate steroid hormones and is abnormally expressed in many cancers. According to whether the tumor can be affected by hormones, we divide malignancies into hormone-dependent and hormone-independent types. Studies have shown that AKR1C2 is involved in regulating tumor invasion, migration, and other malignant phenotypes, eliminating reactive oxygen species (ROS), promoting chemotherapy resistance of tumor cells, and has prognostic value in some cancers. Here, we focus on the role and clinical significance of AKR1C2 in different types of tumors.

AKR1B10 regulates M2 macrophage polarization to promote the malignant phenotype of gastric cancer.

BACKGROUND: Immunotherapy has brought new hope to gastric cancer (GC) patients. Exploring the immune infiltration pattern in GC and the key molecules is critical for optimizing the efficacy of immunotherapy. Aldo-keto reductase family 1 member B10 (AKR1B10) is an inflammatory regulator and is closely related to the prognosis of patients with GC. However, the function of AKR1B10 in GC remains unclear. METHODS: In the present study, the CIBERSORT algorithm was used to analyze the immune infiltration pattern in 373 samples in the Cancer Genome Atlas (TCGA) database. Differentially expressed genes (DEGs) were seared by combing the TCGA database and the Gene Expression Omnibus (GEO) database, and the key molecule AKR1B10 was identified by weighted gene coexpression network analysis (WGCNA). The biological functions of AKR1B10 in stomach adenocarcinoma (STAD) were investigated in vitro. RESULTS: Macrophage polarization was the main immune infiltration pattern in GC, and the state of macrophage polarization was closely related to the pathological grading of GC and the clinical stage of patients. AKR1B10, MUC5AC, TFF2, GKN1, and PGC were significantly down-regulated in GC tissues. Low AKR1B10 expression induced M2 macrophage polarization and promoted the malignant phenotype of GC. CONCLUSION: M2 macrophage polarization is the main immune infiltration pattern in GC. Low AKR1B10 expression induces M2 macrophage polarization and promotes the malignant transformation of GC.

AKR7A3 modulates the metastasis of pancreatic ductal adenocarcinoma through regulating PHGDH-suppressed autophagy.

AKR7A3 is a member of the aldo-keto reductase (AKR) protein family, whose primary purpose is to reduce aldehydes and ketones to generate primary and secondary alcohols. It has been reported that AKR7A3 is downregulated in pancreatic cancer (PC). However, the mechanism underlying the effects of AKR7A3 in PC remains largely unclarified. Here, we explored the biological function, molecular mechanism and clinical relevance of AKR7A3 in pancreatic ductal adenocarcinoma (PDAC). AKR7A3 expression was downregulated in PDAC compared with adjacent normal tissues, and the lower AKR7A3 expression was related to poor prognosis. In addition, our results demonstrated that AKR7A3 could be a potential diagnostic marker for PDAC, especially in the early stages. Knockdown of AKR7A3 promoted PDAC progression and chemoresistance, while inhibiting autophagy flux. Mechanistically, AKR7A3 affected the metastasis, autophagy, and chemoresistance of PDAC by regulating PHGDH. Overall, the present study suggests that AKR7A3 inhibits PDAC progression by regulating PHGDH-induced autophagy. In addition, AKR7A3 inhibits chemoresistance via regulating PHGDH and may serve as a new therapeutic target for PDAC.

Germline Mutations in Steroid Metabolizing Enzymes: A Focus on Steroid Transforming Aldo-Keto Reductases.

Steroid hormones synchronize a variety of functions throughout all stages of life. Importantly, steroid hormone-transforming enzymes are ultimately responsible for the regulation of these potent signaling molecules. Germline mutations that cause dysfunction in these enzymes cause a variety of endocrine disorders. Mutations in SRD5A2, HSD17B3, and HSD3B2 genes that lead to disordered sexual development, salt wasting, and other severe disorders provide a glimpse of the impacts of mutations in steroid hormone transforming enzymes. In a departure from these established examples, this review examines disease-associated germline coding mutations in steroid-transforming members of the human aldo-keto reductase (AKR) superfamily. We consider two main categories of missense mutations: those resulting from nonsynonymous single nucleotide polymorphisms (nsSNPs) and cases resulting from familial inherited base pair substitutions. We found mutations in human AKR1C genes that disrupt androgen metabolism, which can affect male sexual development and exacerbate prostate cancer and polycystic ovary syndrome (PCOS). Others may be disease causal in the AKR1D1 gene that is responsible for bile acid deficiency. However, given the extensive roles of AKRs in steroid metabolism, we predict that with expanding publicly available data and analysis tools, there is still much to be uncovered regarding germline AKR mutations in disease.

Comparison of Glyphosate-Degradation Ability of Aldo-Keto Reductase (AKR4) Proteins in Maize, Soybean and Rice.

Genes that participate in the degradation or isolation of glyphosate in plants are promising, for they endow crops with herbicide tolerance with a low glyphosate residue. Recently, the aldo-keto reductase (AKR4) gene in Echinochloa colona (EcAKR4) was identified as a naturally evolved glyphosate-metabolism enzyme. Here, we compared the glyphosate-degradation ability of theAKR4 proteins from maize, soybean and rice, which belong to a clade containing EcAKR4 in the phylogenetic tree, by incubation of glyphosate with AKR proteins both in vivo and in vitro. The results indicated that, except for OsALR1, the other proteins were characterized as glyphosate-metabolism enzymes, with ZmAKR4 ranked the highest activity, and OsAKR4-1 and OsAKR4-2 exhibiting the highest activity among the AKR4 family in rice. Moreover, OsAKR4-1 was confirmed to endow glyphosate-tolerance at the plant level. Our study provides information on the mechanism underlying the glyphosate-degradation ability of AKR proteins in crops, which enables the development of glyphosate-resistant crops with a low glyphosate residue, mediated by AKRs.

Genome-Wide Identification and Characterization of Aldo-Keto Reductase (AKR) Gene Family in Response to Abiotic Stresses in Solanum lycopersicum.

Tomato is one of the most popular and nutritious vegetables worldwide, but their production and quality are threatened by various stresses in the environment in which they are grown. Thus, the resistance and tolerance of tomatoes to various biotic and abiotic stresses should be improved. Aldo-keto reductases (AKR) are a superfamily of NAD(P)(H)-dependent oxidoreductases that play multiple roles in abiotic and biotic stress defenses by detoxification and reactive oxygen species (ROS) clearance pathways. Here, 28 identified AKR family genes of tomatoes were identified genome-wide, and their characteristics, including chromosomal location, gene structures, protein motifs, and system evolution, were analyzed. Furthermore, the phylogenetic and syntenic relationships in Arabidopsis thaliana, rice, and tomatoes were compared. Expression patterns at different tissues and in response to abiotic stresses, such as drought and salt, were monitored to further explore the function of SlAKRs. Finally, three SlAKRs candidate genes were silenced by Virus induced gene silencing (VIGS) systems in Solanum lycopersicum, showing sensitivity to drought and salt stresses with low contents of proline (Pro) and peroxidase (POD) and high content of malonaldehyde (MDA). This study provides the characteristics and potential functions of SlAKRs in response to abiotic stresses that will be helpful for further studies in S. lycopersicum.