Biochemical and Physiological Responses of Cucumis sativus Cultivars to Different Combinations of Low-Temperature and High Humidity

Low-temperature and high humidity are typical environmental factors in the plastic tunnel and solar greenhouse during the cold season that restricts plant growth and development. Herein, we investigated the impact of different combinations of low-temperature and high humidity (day/night: T1 15/10 °C?+?95%, T2 12/8 °C?+?95%, and T3 9/5 °C?+?95%) along with a control (CK 25/18 °C?+?80%) on cucumber cultivars viz: Zhongnong37 (ZN37: resistant) and Shuyanbailv (SYB: sensitive). The low-temperature and high humidity stresses increased electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and intercellular concentration of carbon dioxide (Ci), and reduced morphological indices, relative water content (RWC), net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (E) and leaf pigments in both cultivars as compared to control (CK). Superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were decreased in cv. SYB under stress conditions as compared to cv. ZN37. Low-temperature and high humidity treatments showed an increase in proline and soluble protein content in cv. ZN37 as compared to cv. SYB. Abscisic acid (ABA) and jasmonic acid (JA) were augmented while indole-3-acetic acid (IAA), zeatin (ZT), zeatin riboside (ZR), and gibberellic acid (GA) were decreased in both cultivars. Under T3 (9/5 °C?+?95%), Pn, protoporphyrin, and ZT were extremely decreased by 71.3%, 74.3%, and 82.4%, respectively, in cv. SYB compared to control. Moreover, principal component analysis (PCA) based on physiochemical traits confirmed that cv. ZN37 had the strongest correlation with antioxidant enzymes, proline, and soluble protein content than cv. SYB under low-temperature and high humidity treatments. Our results suggest that a stress-tolerant cultivar mitigates stress damage in cucumber transplants by regulating photosynthetic efficiency, antioxidant capacity and hormonal profile when compared to a stress-sensitive cultivar.

     

Abutilon indicum Exhibits Anxiolytic and Antidepressant Effects in Mice Models

Doklady Biochemistry and Biophysics - Abutilon indicum Linn (A. indicum) is native to tropical and subtropical zones and traditionally used in ulcer, diabetes, piles, jaundice, gonorrhoea and...     

Definition of an inhibitory juxtamembrane WW-like domain in the platelet-derived growth factor beta receptor

A variety of tumors contain activating mutations in the cytoplasmic juxtamembrane domain of the type III family of receptor-tyrosine kinases, and some constructed mutations in this domain induce ligand-independent receptor activation. To explore the role of this domain in regulation of receptor activity, we subjected the juxtamembrane domain of the murine platelet-derived growth factor (PDGF) beta receptor to alanine-scanning mutagenesis. The mutant receptors were expressed in Ba/F3 cells and tested for constitutive tyrosine phosphorylation, association with phosphatidylinositol 3'-kinase, and their ability to induce cell survival and proliferation in the absence of interleukin-3. The mutant receptors accumulated to similar levels and appeared to undergo a normal PDGF-induced increase in tyrosine phosphorylation. Alanine substitutions at numerous positions located throughout the juxtamembrane domain caused constitutive receptor activation, as did an alanine insertion in the membrane-proximal segment of the juxtamembrane domain and a six-amino acid deletion in the center of the domain. It is possible to model the PDGF receptor juxtamembrane domain as a short alpha-helix followed by a three-stranded beta-sheet very similar to the known structures of WW domains. Strikingly, the activating mutations clustered in the central portions of the first and second beta strands and along one face of the beta-sheet, whereas the loops connecting the strands were largely devoid of mutationally sensitive positions. These findings provide strong support for the model that the activating mutations in the juxtamembrane region stimulate receptor activity by disrupting an inhibitory WW-like domain.     

Pandemic strains of O3:K6 Vibrio parahaemolyticus in the aquatic environment of Bangladesh

A total of 1500 environmental strains of Vibrio parahaemolyticus, isolated from the aquatic environment of Bangladesh, were screened for the presence of a major V. parahaemolyticus virulence factor, the thermostable direct haemolysin (tdh) gene, by the colony blot hybridization method using a digoxigenin-labeled tdh gene probe. Of 1500 strains, 5 carried the tdh sequence, which was further confirmed by PCR using primers specific for the tdh gene. Examination by PCR confirmed that the 5 strains were V. parahaemolyticus and lacked the thermostable direct haemolysin-related haemolysin (trh) gene, the alternative major virulence gene known to be absent in pandemic strains. All 5 strains gave positive Kanagawa phenomenon reaction with characteristic beta-haemolysis on Wagatsuma agar medium. Southern blot analysis of the HindIII-digested chromosomal DNA demonstrated, in all 5 strains, the presence of 2 tdh genes common to strains positive for Kanagawa phenomenon. However, the 5 strains were found to belong to 3 different serotypes (O3:K29, O4:K37, and O3:K6). The 2 with pandemic serotype O3:K6 gave positive results in group-specific PCR and ORF8 PCR assays, characteristics unique to the pandemic clone. Clonal variations among the 5 isolates were analyzed by comparing RAPD and ribotyping patterns. Results showed different patterns for the 3 serotypes, but the pattern was identical among the O3:K6 strains. This is the first report on the isolation of pandemic O3:K6 strains of V. parahaemolyticus from the aquatic environment of Bangladesh.     

Human-mediated introgression of exotic chukar (Alectoris chukar, Galliformes) genes from East Asia into native Mediterranean partridges

Mediterranean red-legged (Alectoris rufa) and rock (Alectoris graeca) partridge populations are affected by genetic pollution. The chukar partridge (Alectoris chukar), a species only partly native to Europe, is the most frequently introgressive taxon detected in the genome of hybrid partridges. Both theoretical (evolutionary) and practical (resources management) matters spur to get insight into the geographic origin of the A. chukar hybridizing swarm. The phenotypic A. rufa populations colonizing the easternmost part of the distribution range of this species, the islands of Elba (Italy) and Corsica (France), were investigated. The analysis of both mitochondrial (mtDNA: Cytochrome-b gene plus Control Region: 2,250 characters) and nuclear (Short Tandem Repeats, STR; Random Amplified Polymorphic DNA, RAPD) genomes of 25 wild (Elba) and 20 captive (Corsica) partridges, disclosed spread introgression of chukar origin also in these populations. All mtDNA haplotypes of Elba and Corsica partridges along with those we obtained from other A. rufa (total, n = 111: Italy, Spain, France) and A. graeca (n = 6, Italy), were compared with the mtDNA haplotypes of chukars (n = 205) sampled in 20 countries. It was found that the A. chukar genes detected in red-legged (n = 43) and rock partridges (n = 4) of Spain, France and Italy as well as in either introduced (Italy) or native (Greece, Turkey) chukars (n = 35) were all from East Asia. Hence, a well-defined geographic origin of the exotic chukar genes polluting the genome of native Mediterranean A. rufa and A. graeca (inter-specific level) as well as A. chukar (intra-specific level), was demonstrated.     

Synthesis and evaluation of in vitro antiviral activity of novel phenoxy acetic acid derivatives

Several substituted phenoxy acetic acid derived pyrazolines were synthesized by the reaction between 2-{4-[3-(2,4-dihydroxyphenyl)-3-oxo-1-propenyl]-2-methoxyphenoxy} acetic acid and substituted acid hydrazides and were tested for their in vitro cytotoxicity and antiviral activity. None of the compounds showed any specific antiviral activity [50% antivirally effective concentration (EC(50)) > or = 5-fold lower than minimum cytotoxic concentration]. The most cytotoxic of the series was 2-{4-[3-(2,4-dihydroxyphenyl)-1-(2-hydroxybenzoyl-4,5-dihydro-1H-5-pyrazolyl]-2-methoxyphenoxy}acetic acid (3(j)), with a minimum cytotoxic concentration of 0.16 microg/mL in human embryonic lung (HEL) cells.     

Glycosyltransferases from Oat (Avena) Implicated in the Acylation of Avenacins

Plants produce a huge array of specialized metabolites that have important functions in defense against biotic and abiotic stresses. Many of these compounds are glycosylated by family 1 glycosyltransferases (GTs). Oats (Avena spp.) make root-derived antimicrobial triterpenes (avenacins) that provide protection against soil-borne diseases. The ability to synthesize avenacins has evolved since the divergence of oats from other cereals and grasses. The major avenacin, A-1, is acylated with N-methylanthranilic acid. Previously, we have cloned and characterized three genes for avenacin synthesis (for the triterpene synthase SAD1, a triterpene-modifying cytochrome P450 SAD2, and the serine carboxypeptidase-like acyl transferase SAD7), which form part of a biosynthetic gene cluster. Here, we identify a fourth member of this gene cluster encoding a GT belonging to clade L of family 1 (UGT74H5), and show that this enzyme is an N-methylanthranilic acid O-glucosyltransferase implicated in the synthesis of avenacin A-1. Two other closely related family 1 GTs (UGT74H6 and UGT74H7) are also expressed in oat roots. One of these (UGT74H6) is able to glucosylate both N-methylanthranilic acid and benzoic acid, whereas the function of the other (UGT74H7) remains unknown. Our investigations indicate that UGT74H5 is likely to be key for the generation of the activated acyl donor used by SAD7 in the synthesis of the major avenacin, A-1, whereas UGT74H6 may contribute to the synthesis of other forms of avenacin that are acylated with benzoic acid.     

Cholesterol precursors stabilize ordinary and ceramide-rich ordered lipid domains (lipid rafts) to different degrees. Implications for the Bloch hypothesis and sterol biosynthesis disorders

Genetic disorders of cholesterol biosynthesis result in accumulation of cholesterol precursors and cause severe disease. We examined whether cholesterol precursors alter the stability and properties of ordered lipid domains (rafts). Tempo quenching of a raft-binding fluorophore was used to measure raft stability in vesicles containing sterol, dioleoylphosphatidylcholine, and one of the following ordered domain-forming lipids/lipid mixtures: dipalmitoylphosphatidylcholine (DPPC), sphingomyelin (SM), a SM/cerebroside mixture or a SM/ceramide (cer) mixture. Relative to cholesterol, early cholesterol precursors containing an 8-9 double bond (lanosterol, dihydrolanosterol, zymosterol, and zymostenol) only weakly stabilized raft formation by SM or DPPC. Desmosterol, a late precursor containing the same 5-6 double bond as cholesterol, but with an additional 24-25 double bond, also stabilized domain formation weakly. In contrast, two late precursors containing 7-8 double bonds (lathosterol and 7-dehydrocholesterol) were better raft stabilizers than cholesterol. For vesicles containing SM/cerebroside and SM/cer mixtures the effect of precursor upon raft stability was small, although the relative effects of different precursors were the same. Using both detergent resistance and a novel assay involving fluorescence quenching induced by certain sterols we found cholesterol precursors were displaced from cer-rich rafts, and could displace cer from rafts. Precursor displacement by cer was inversely correlated to precursor raft-stabilizing abilities, whereas precursor displacement of cer was greatest for the most highly raft-stabilizing precursors. These observations support the hypothesis that sterols and cer compete for raft-association (Megha, and London, E. (2004) J. Biol. Chem. 279, 9997-10004). The results of this study have important implications for how precursors might alter raft structure and function in cells, and for the Bloch hypothesis, which postulates that sterol properties are gradually optimized for function along the biosynthetic pathway.