Ascorbate peroxidase from Jatropha curcas enhances salt tolerance in transgenic Arabidopsis

Expression analysis of PIN family genes in Chinese hickory reveals their potential roles during grafting and salt stress

Grafting is an effective way to improve Chinese hickory while salt stress has caused great damage to the Chinese hickory industry. Grafting and salt stress have been regarded as the main abiotic stress types for Chinese hickory. However, how Chinese hickory responds to grafting and salt stress is less studied. Auxin has been proved to play an essential role in the stress response through its re-distribution regulation mediated by polar auxin transporters, including PIN-formed (PIN) proteins. In this study, the PIN gene family in Chinese hickory (CcPINs) was identified and structurally characterized for the first time. The expression profiles of the genes in response to grafting and salt stress were determined. A total of 11 CcPINs with the open reading frames (ORFs) of 1,026-1,983 bp were identified. Transient transformation in tobacco leaves demonstrated that CcPIN1a, CcPIN3, and CcPIN4 were localized in the plasma membrane. There were varying phylogenetic relationships between CcPINs and homologous genes in different species, but the closest relationships were with those in Carya illinoinensis and Juglans regia. Conserved N- and C-terminal transmembrane regions as well as sites controlling the functions of CcPINs were detected in CcPINs. Five types of cis-acting elements, including hormone- and stress-responsive elements, were detected on the promoters of CcPINs. CcPINs exhibited different expression profiles in different tissues, indicating their varied roles during growth and development. The 11 CcPINs responded differently to grafting and salt stress treatment. CcPIN1a might be involved in the regulation of the grafting process, while CcPIN1a and CcPIN8a were related to the regulation of salt stress in Chinese hickory. Our results will lay the foundation for understanding the potential regulatory functions of CcPIN genes during grafting and under salt stress treatment in Chinese hickory.

The Variability for the Biochemical Indicators at the Winter Wheat Assortment and Identifying the Sources with a High Antioxidant Activity

This study presents the variability of some biochemical indicators in the winter wheat assortments tested in south-western Oltenia (Romania) and identification of the sources showing a high antioxidant activity. The peroxidase activity has intensified as the stress induced by treatment with PEG of different concentrations and in different doses increased. Regarding the peroxidase content, among the varieties treated with PEG 10,000 25%, the majority of the Romanian varieties tested showed higher values of the PEG/control treatment ratio, which suggests tolerance to drought. In reverse, the activity of ascorbate peroxidase is lower in tolerant varieties. The varieties with a subunit report have been noted. Among them are the Izvor variety, known as the drought-tolerant variety, as well as other Romanian varieties: Alex, Delabrad, Lovrin 34, etc. An increased activity of catalase was present in most varieties, so there is the possibility of drought tolerance. Among the varieties highlighted are Romanian varieties (Dropia, Trivale, Nikifor, etc.) but also foreign varieties (Kristina, GH Hattyu, Karlygash, etc.). However, the correlation between yield index in the limited assortment and the antioxidant enzyme content ratios between PEG and control treatments does not exist, suggesting that none of these biochemical indicators are a selective indicator for drought tolerance under the experimental condition.

Hsa_circ_0074491 regulates the malignance of cholesteatoma keratinocytes by modulating the PI3K/Akt pathway by binding to miR-22-3p and miR-125a-5p: An observational study

Cholesteatoma is a benign cystic lesion that can continue to grow like a tumor. Circular ribonucleic acid (RNA) hsa_circ_0074491 (circ_0074491) has been reported to be down-regulated in cholesteatoma tissues. However, the role and regulatory mechanism of circ_0074491 in the growth of cholesteatoma are unclear.The expression of circ_0074491, microRNA (miR)-22-3p, and miR-125a-5p in cholesteatoma tissues was detected by quantitative real-time polymerase chain reaction. The proliferation, cell cycle, apoptosis, migration, and invasion of cholesteatoma keratinocytes were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, plate clone, flow cytometry, or transwell assays. Several protein levels were examined by western blotting. The targeting relationship between miR-22-3p or miR-125a-5p and circ_0074491 was verified via dual-luciferase reporter and RNA pull-down assays.We observed the downregulation of circ_0074491 in cholesteatoma tissues. Furthermore, circ_0074491 knockdown facilitated cell proliferation, migration, invasion, and repressed cell apoptosis in cholesteatoma keratinocytes. Circ_0074491 was verified as a decoy for miR-22-3p and miR-125a-5p in cholesteatoma keratinocytes. Both miR-22-3p and miR-125a-5p silencing reversed the impacts of circ_0074491 silencing on proliferation, apoptosis, migration, and invasion of cholesteatoma keratinocytes. Also, circ_0074491 knockdown activated the PI3K/Akt pathway in cholesteatoma keratinocytes via miR-22-3p and miR-125a-5p.Circ_0074491 played a suppressive role in cholesteatoma through inactivating the PI3K/Akt pathway via binding to miR-22-3p and miR-125a-5p, which provided a novel evidence for the involvement of circRNA in the development of cholesteatoma.

Progressive Genomic Approaches to Explore Drought- and Salt-Induced Oxidative Stress Responses in Plants under Changing Climate

Drought and salinity are the major environmental abiotic stresses that negatively impact crop development and yield. To improve yields under abiotic stress conditions, drought- and salinity-tolerant crops are key to support world crop production and mitigate the demand of the growing world population. Nevertheless, plant responses to abiotic stresses are highly complex and controlled by networks of genetic and ecological factors that are the main targets of crop breeding programs. Several genomics strategies are employed to improve crop productivity under abiotic stress conditions, but traditional techniques are not sufficient to prevent stress-related losses in productivity. Within the last decade, modern genomics studies have advanced our capabilities of improving crop genetics, especially those traits relevant to abiotic stress management. This review provided updated and comprehensive knowledge concerning all possible combinations of advanced genomics tools and the gene regulatory network of reactive oxygen species homeostasis for the appropriate planning of future breeding programs, which will assist sustainable crop production under salinity and drought conditions.

Identification and Characterization of the APX Gene Family and Its Expression Pattern under Phytohormone Treatment and Abiotic Stress in Populus trichocarpa

Ascorbate peroxidase (APX) is a member of class I of the heme-containing peroxidase family. The enzyme plays important roles in scavenging reactive oxygen species for protection against oxidative damage and maintaining normal plant growth and development, as well as in biotic stress responses. In this study, we identified 11 APX genes in the Populus trichocarpa genome using bioinformatic methods. Phylogenetic analysis revealed that the PtrAPX proteins were classifiable into three clades and the members of each clade shared similar gene structures and motifs. The PtrAPX genes were distributed on six chromosomes and four segmental-duplicated gene pairs were identified. Promoter cis-elements analysis showed that the majority of PtrAPX genes contained a variety of phytohormone- and abiotic stress-related cis-elements. Tissue-specific expression profiles indicated that the PtrAPX genes primarily function in roots and leaves. Real-time quantitative PCR (RT-qPCR) analysis indicated that PtrAPX transcription was induced in response to drought, salinity, high ammonium concentration, and exogenous abscisic acid treatment. These results provide important information on the phylogenetic relationships and functions of the APX gene family in P. trichocarpa.

Groundnut AhcAPX conferred abiotic stress tolerance in transgenic banana through modulation of the ascorbate-glutathione pathway

A stress inducible cytosolic ascorbate peroxidase gene (AhcAPX) was ectopically expressed in banana (cv. Grand naine) plants to strengthen their antioxidant capacity. High level of AhcAPX gene transcripts and enzyme suggested constitutive and functional expression of candidate gene in transgenic (TR) plants. The tolerance level of in vitro and in vivo grown TR banana plantlets were assessed against salt and drought stress. The TR banana plants conferred tolerance against the abiotic stresses by maintaining a high redox state of ascorbate and glutathione, which correlated with lower accumulation of H₂O₂, O₂ ^⋅- and higher level of antioxidant enzyme (SOD, APX, CAT, GR, DHAR and MDHAR) activities. The efficacy of AhcAPX over-expression was also investigated in terms of different physiochemical attributes of TR and untransformed control plants, such as, proline content, membrane stability, electrolyte leakage and chlorophyll retention. The TR plants showed higher photochemical efficiency of PSII (Fv/Fm), and stomatal attributes under photosynthesis generated reactive oxygen species (ROS) stress. The outcome of present investigation suggest that ectopic expression of AhcAPX gene in banana enhances the tolerance to drought and salt stress by annulling the damage caused by ROS.

Abiotic Stress Tolerance in Plants: Myriad Roles of Ascorbate Peroxidase

One of the most significant manifestations of environmental stress in plants is the increased production of Reactive Oxygen Species (ROS). These ROS, if allowed to accumulate unchecked, can lead to cellular toxicity. A battery of antioxidant molecules is present in plants for keeping ROS levels under check and to maintain the cellular homeostasis under stress. Ascorbate peroxidase (APX) is a key antioxidant enzyme of such scavenging systems. It catalyses the conversion of H₂O₂ into H₂O, employing ascorbate as an electron donor. The expression of APX is differentially regulated in response to environmental stresses and during normal plant growth and development as well. Different isoforms of APX show differential response to environmental stresses, depending upon their sub-cellular localization, and the presence of specific regulatory elements in the upstream regions of the respective genes. The present review delineates role of APX isoforms with respect to different types of abiotic stresses and its importance as a key antioxidant enzyme in maintaining cellular homeostasis.

Expression Patterns of Genes Involved in Ascorbate-Glutathione Cycle in Aphid-Infested Maize (Zea mays L.) Seedlings

Reduced forms of ascorbate (AsA) and glutathione (GSH) are among the most important non-enzymatic foliar antioxidants in maize (Zea mays L.). The survey was aimed to evaluate impact of bird cherry-oat aphid (Rhopalosiphum padi L.) or grain aphid (Sitobion avenae F.) herbivory on expression of genes related to ascorbate-glutathione (AsA-GSH) cycle in seedlings of six maize varieties (Ambrozja, Nana, Tasty Sweet, Touran, Waza, Złota Karłowa), differing in resistance to the cereal aphids. Relative expression of sixteen maize genes encoding isoenzymes of ascorbate peroxidase (APX1, APX2, APX3, APX4, APX5, APX6, APX7), monodehydroascorbate reductase (MDHAR1, MDHAR2, MDHAR3, MDHAR4), dehydroascorbate reductase (DHAR1, DHAR2, DHAR3) and glutathione reductase (GR1, GR2) was quantified. Furthermore, effect of hemipterans’ attack on activity of APX, MDHAR, DHAR and GR enzymes, and the content of reduced and oxidized ascorbate and glutathione in maize plants were assessed. Seedling leaves of more resistant Z. mays varieties responded higher elevations in abundance of target transcripts. In addition, earlier and stronger aphid-triggered changes in activity of APX, MDHAR, DHAR and GR enzymes, and greater modulations in amount of the analyzed antioxidative metabolites were detected in foliar tissues of highly resistant Ambrozja genotype in relation to susceptible Tasty Sweet plants.