Cyanobacteria-mediated phenylpropanoids and phytohormones in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis>) enhance plant growth and stress tolerance

Phenylpropanoids, flavonoids and plant growth regulators in rice (Oryza sativa) variety (UPR 1823) inoculated with different cyanobacterial strains namely Anabaena oryzae, Anabaena doliolum, Phormidium fragile, Calothrix geitonos, Hapalosiphon intricatus, Aulosira fertilissima, Tolypothrix tenuis, Oscillatoria acuta and Plectonema boryanum were quantified using HPLC in pot conditions after 15 and 30 days. Qualitative analysis of the induced compounds using reverse phase HPLC and further confirmation with LC-MS/MS showed consistent accumulation of phenolic acids (gallic, gentisic, caffeic, chlorogenic and ferulic acids), flavonoids (rutin and quercetin) and phytohormones (indole acetic acid and indole butyric acid) in rice leaves. Plant growth promotion (shoot, root length and biomass) was positively correlated with total protein and chlorophyll content of leaves. Enzyme activity of peroxidase and phenylalanine ammonia lyase and total phenolic content was fairly high in rice leaves inoculated with O. acuta and P. boryanum after 30 days. Differential systemic accumulation of phenylpropanoids in plant leaves led us to conclude that cyanobacterial inoculation correlates positively with plant growth promotion and stress tolerance in rice. Furthermore, the study helped in deciphering possible mechanisms underlying plant growth promotion and stress tolerance in rice following cyanobacterial inoculation and indicated the less explored avenue of cyanobacterial colonization in stress tolerance against abiotic stress.     

Effects of arboriculture stands on European hare <Emphasis Type="Italic">Lepus europaeus</Emphasis> spring habitat use in an agricultural area of northern Italy

Habitat changes due to agricultural intensification is widely considered a main cause of European hare (Lepus europaeus Pallas, 1778) decline. We investigated the potential of arboriculture stands to enhance landscape diversity and increase farmland suitability for European hares in an intensive agricultural area of northern Italy. In spring 2005, we recorded hare habitat use during feeding activity and resting time by nocturnal censuses and searching for daytime resting sites, respectively. Hare presence/absence, based on faecal pellets, was assessed in 150 1-m radius plots. Hares positively selected edges and avoided woods and stubble during both feeding activity and resting time, which highlights the key role of permanent linear cover in providing the variety of vegetation types required by hares for shelter and feed. Forms were typically located in covered places, surrounded by denser vegetation than sample plots, in order to gain protection from avian and terrestrial predators. Arboriculture stands seem to be able to satisfy a part of hare habitat requirement, thanks to ground flora that provide tasty food, and tree cover that offers refuge against predators and bad weather conditions. However, more focused studies are necessary to improve knowledge of the long-term effects of these crops on farmland biodiversity.     

TRPM2 Channel Membrane Currents in Primary Rat Megakaryocytes Were Activated by the Agonist ADP-Ribose but Not Oxidative Stress

Melastatin-like transient receptor potential 2 (TRPM2) channel activation/inhibition mechanisms in response to ADP-ribose (ADPR), oxidative stress, flufenamic acid (FFA) and 2-aminoethoxydiphenyl borate (2-APB) are not clear. We tested the effects of FFA and 2-APB on ADPR-induced TRPM2 cation channel currents in rat native bone marrow megakaryocytes. Megakaryocyte cells were freshly isolated from rat bone marrow and studied with the conventional whole-cell patch-clamp technique. Extracellular H₂O₂, FFA and 2-APB were added through the patch chamber, while intracellular ADPR was applied through the pipette. Nonselective cation currents were consistently induced by ADPR but not H₂O₂. Current density of ADPR in the cells was significantly (P < 0.001) higher than in control. The time courses of ADPR effects in the megakaryocytes were characterized by a delay of 2.24 ± 0.73. The ADPR-induced Ca²⁺ gate was not blocked by either the IP₃ receptor inhibitor 2-APB or the PLC inhibitor FFA. In conclusion, TRPM2 channels were constitutively activated by intracellular ADPR, although the channel currents in rat native megakaryocytes were not affected by extracellular H₂O₂, 2-APB or FFA. Activation of TRPM2 channels in megakaryocytes seems to be intracellular and ADPR-dependent.     

Expression patterns of two <Emphasis Type="Italic">Arabidopsis</Emphasis> endo-β-1,4-glucanase genes (<Emphasis Type="Italic">At3g43860, At4g39000</Emphasis>) in reproductive development

Endo-β-1,4-D-glucanases (EGases) are a widespread and vital group of glycosyl hydrolases that generally break the β-1,4-glucosyl linkages. Studies of plant EGases have mainly been concentrated on vegetative growth, while little is currently known about their role in reproductive processes. Using the GUS reporter aided analysis of promoter activities, we identified the expression patterns of two putative Arabidopsis EGases genes (At3g43860 and At4g39000) whose promoters conferred specific localization of the GUS activity in reproductive organs. We found that At3g43860, which is similar to KOR in its protein structural organization, is expressed in mature pollen and the pollen tube, implying that it may have a role in pollen and pollen tube growth. At4g39000 was found to be activated in the developing ovules and seeds, especially at the micropylar end of the inner integuments and nucellus in a proximal-distal pattern. Our results suggested that the two EGases play specific roles in Arabidopsis sexual reproduction.     

Chromosome polymorphism in <Emphasis Type="Italic">Rineloricaria pentamaculata</Emphasis> (Loricariidae,Siluriformes) of the Paraná River basin

Cytogenetic analysis in three Rineloricaria pentamaculata populations revealed diploid number 2n = 56 chromosomes, karyotype formula 8m/sm + 48st/a and FN = 64. Owing to the presence of the heteromorphic chromosome pair with a big submetacentric chromosome and a small acrocentric one in both males and females, 42.9% of specimens in the Tauá Stream population had the karyotype formula 9m/sm + 47st/a and FN = 65. Analysis of the nucleolus-organizing region by Ag-NOR and FISH techniques showed a single NOR system at pair 5 for R. pentamaculata populations of the Keller River and the Tauá Stream. However, specimens of populations of the Tatupeba Stream had multiple NOR systems at pairs 5 and 8. A constitutive heterochromatin pattern in R. pentamaculata is mainly distributed in the pericentromeric and telomeric regions with interstitial markers in certain chromosomes. Heterochromatin is located in the telomeric and centromeric positions of the acrocentric chromosome in the heteromorphic pair of the Tauá Stream population. In the submetacentric chromosome the markings are located in the telomeric (short arm), pericentomeric and interstitial (long arm) positions. The origins of polymorphisms are discussed.     

Action of ferric and aluminium ions on the dormancy breakage of <Emphasis Type="Italic">Stylosanthes humilis</Emphasis> seeds

Dormancy of scarified seeds of Stylosanthes humilis was broken by acidic Al³⁺ and Fe³⁺ solutions. Fe⁺³-stimulated seeds exhibited a high activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and produced great amounts of ethylene, which showed correlated with the germination process. In addition, specific inhibitors of ethylene biosynthesis and action largely depressed the Fe³⁺-stimulated germination, leading to the conclusion that the ion broke dormancy by triggering ethylene production by the seeds. By contrast, inhibitors of ethylene biosynthesis and action did not impair germination of Al³⁺-stimulated dormant seeds. Moreover, ethylene production and activity of ACC oxidase of Al³⁺-treated seeds was substantially decreased by inhibitors of ethylene biosynthesis, but germination kept large. Together these data suggest that ethylene biosynthesis was not required in the chain of events triggered by Al³⁺ leading to dormancy breakage. Methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of seeds to the same extent as Al³⁺ did. Germination of both Al³⁺- and MV-stimulated dormant seeds was inhibited by sodium selenate, an antioxidant compound; selenate, however had no effect on germination of Fe³⁺-stimulated seeds. Together these data indicate that the mechanisms underlying the germination of Al³⁺- and Fe³⁺-treated seeds are not the same.     

Light activation of the isomerization and deprotonation of the protonated Schiff base retinal

We perform an ab initio analysis of the photoisomerization of the protonated Schiff base of retinal (PSB-retinal) from 11-cis to 11-trans rotating the C10-C11=C12-C13 dihedral angle from 0° (cis) to -180° (trans). We find that the retinal molecule shows the lowest rotational barrier (0.22 eV) when its charge state is zero as compared to the barrier for the protonated molecule which is ∼0.89 eV. We conclude that rotation most likely takes place in the excited state of the deprotonated retinal. The addition of a proton creates a much larger barrier implying a switching behavior of retinal that might be useful for several applications in molecular electronics. All conformations of the retinal compound absorb in the green region with small shifts following the dihedral angle rotation; however, the Schiff base of retinal (SB-retinal) at trans-conformation absorbs in the violet region. The rotation of the dihedral angle around the C11=C12 π-bond affects the absorption energy of the retinal and the binding energy of the SB-retinal with the proton at the N-Schiff; the binding energy is slightly lower at the trans-SB-retinal than at other conformations of the retinal.