Activity of the aldehyde and alcohol of gibberellins A12 and A14, two derivatives of gibberellin A15 and four decomposition products of gibberellin A3 in 13 plant bioassays

Summary The biological activities of the aldehyde and alcohol of gibberellins (GAs) A₁₂ and A₁₄, 3-OH-GA₁₅, 3-OH-GA₁₅ wrong lactone (i.e. GA₃₇ wrong lactone) and the four major decomposition products of GA₃ (isogibberellic, allogibberic, epiallogibberic and 9(11)-dehydroallogibberic acids) were tested over a wide range of concentrations on 13 plant bioassays in order to ascertain certain of the structural requirements for biological activity. Generally modification of the basic GA-molecule decreased its activity in all assays except for derivatives of GA₁₂ and GA₁₄ (suggesting conversion of these derivatives to more polar, active GAs). Modification of the 3-OH from the usual 3 to 3 configuration markedly reduced activity. Neither the presence of an inverted lactone ring (i.e. 3-OH-GA₁₅ wrong lactone) nor changes to the lactone ring of GA₃ (410) to form iso-GA₃ (42) appreciably reduce activity. Further decomposition of GA₃ to allogibberic and 9(11)-dehydroallogibberic acid reduced activity only slightly, but epimerization of allogibberic acid at C-9 essentially eliminated biological activity.     

Conversion of gibberellin A14 to other gibberellins in seedlings of dwarf Pisum sativum

Gibberellin A₁₄-[17-³H] applied to seedlings of dark grown dwarf pea (Pisum sativum L. cy. Meteor) was converted to GA₁, GA₈, GA₁₈, GA₂₃, GA₂₈, and GA₃₈. The sequence of interconversion of GA₁₄→ GA₁₈ → GA₃₈ → GA₂₃ → GA₁ → GA₈ is indicated. Identifications were made by gas-liquid radiochromatography using three liquid stationary phases.     

Ab initio molecular dynamics of the reactivity of vitamin C toward hydroxyl and $$ {HO}_2/{O}_2^{-} $$ radicals

Vitamin C is one of the most abundant exogenous antioxidants in the cell, and it is of the utmost importance to elucidate its mechanism of action against radicals. In this study, the reactivity of vitamin C toward OH and \( {HO}_2/{O}_2^{-} \) radicals in aqueous medium was analyzed by ab initio molecular dynamics using CPMD code. The simulations led to results similar to those of static studies or experiments for the pair of \( {HO}_2/{O}_2^{-} \) radicals but bring new insights for the reactivity with hydroxyl radical: the reaction takes place before the formation of an adduct and consists of two steps: first an electron is transferred to hydroxyl radical and then the ascorbyl radical loses a proton.

Open image in new window

Graphical Abstract Reactivity of vitamin C toward hydroxyl and \( {HO}_2/{O}_2^{-} \) radicals

     

A comparison of two methods for assessing critical flicker fusion frequency in hens

This paper compared two general methods for assessing critical fusion frequency in hens (gallus gallus domesticus). The first method was a conditional discrimination procedure with the stimuli presented successively. The second was a two-alternative forced-choice procedure with the stimuli presented simultaneously. It was found that both methods of stimulus presentation gave comparable results suggesting that either method is useful when investigating psychophysics in animals. The results also show that hens’ critical fusion frequency is considerably higher than that of humans which may account for hens’ inability to recognise images presented on standard computer or television monitors.     

Chloroplasts and the biosynthesis and catabolism of abscisic acid

Chloroplast preparations from the mesocarp ofPersea gratissima and from light-grown shoots ofPisum sativum were unable to synthesize abscisic acid (ABA) from mevalonolactone, mevalonic acid, or isopentenyl pyrophosphate. Similar plastid preparations transformed [2-¹⁴C]ABA into acidic products that were chromatographically similar to those generated byP. gratissima mesocarp slices and excised shoots ofP. sativum. Attempts to increase ABA catabolism in chloroplast preparations using sedimentation through Percoll to remove associated proteases also reduced the capacity for ABA catabolism, suggesting that such catabolism arose from contaminating, cytoplasmic enzymes. Both lincomycin and chloramphenicol inhibited the catabolism of ABA by excised shoots ofP. sativum but had little effect on either ABA biosynthesis or ABA catabolism in mesocarp fromP. gratissima. These processes were inhibited markedly by cycloheximide.     

Conformational analysis of macrocyclic frankincense (<Emphasis Type="Italic">Boswellia</Emphasis>) diterpenoids

Frankincense oleoresin has been used in traditional medicine for more than 5000 years. The phytochemistry of frankincense (Boswellia spp.) resins includes triterpenoids (including boswellic acids and their derivatives), diterpenoids (cembrenoids and cneorubenoids), and essential oils. The macrocyclic cembrene diterpenoids may play a part in the biological activities of frankincense resin, but neither the biological targets nor the modes of interaction with the targets are currently known. How these macrocycles interact with biological macromolecules likely depends on what conformation(s) are energetically available to them. In this work, a conformational analysis of 15 Boswellia cembrene diterpenoids and 1 verticillane diterpenoid was carried out at the B3LYP/6-31G* and M06-2X/6-31G* levels of theory, including the SM8 aqueous solvation model. The lowest-energy conformations of boscartin B and incensole oxide were the same as the previously reported X-ray crystal structures, while the lowest-energy conformations of boscartins A and C were very similar to the crystal structures. Boscartins D-H and isoincensole oxide showed only one low-energy conformation for each compound and are predicted to be conformationally locked. Incensole, isoincensolol, and serratol are predicted to be conformationally mobile with several low-energy forms. The conformational mobility of Boswellia cembrenoid diterpenoids depends largely on the degree of epoxidation, either oxirane or tetrahydrofuran rings.     

Evidence of multiple introductions and genetic admixture of the Asian brush-clawed shore crab <Emphasis Type="Italic">Hemigrapsus takanoi</Emphasis> (Decapoda: Brachyura: Varunidae) along the Northern European coast

The Asian brush-clawed shore crab Hemigrapsus takanoi is a non-indigenous species along the Northern European coast. Although the history of range expansion of European H. takanoi has been well-documented, little is known about the genetic compositions of either the introduced European populations or the native Asian ones. We therefore collected H. takanoi broadly from their native Asian sites and introduced European ranges, and genotyped them by sequencing the mitochondrial 16S RNA gene and by analyzing nuclear microsatellite loci. Our results revealed that the H. takanoi Bay of Seine (France) populations consisted of a genetic admixture between populations in Japan and those in the Yellow Sea region. These French populations should be carefully monitored in the future, since the genetic admixture of multiple source populations may accelerate range expansion in non-indigenous organisms. Our results also suggested that shipping lines from East Asia were more probable vectors than historical juvenile oyster transportations from Japan for the foundation of present European H. takanoi populations. Interestingly, gene flow between populations in Japan and those in the Yellow Sea region (i.e., domestic invasion) was not observed despite the higher potential for artificial translocations via shipping lines in the native Asian range compared with those from Asia to Europe. The lack of domestic invasions implied that intra-specific priority effects of the resident H. takanoi populations played an important role in preventing the successful colonization of artificially-transferred individuals.     

Interconversion of gibberellin A5 to gibberellin 3 in seedlings of dwarf Pisum sativum

[³H]-Gibberellin A₅ ([³H]-GA₅) applied to seedlings of dark-grown dwarf pea (Pisum sativum L. cv. Meteor), was converted to two acidic compounds, GA₃ and a chromatographically similar unknown. Identification of GA₃ was made by gas-liquid radiochromatography using three stationary phases.     

Assessing the diversity of New Zealand freshwater harpacticoid copepods (Crustacea: Copepoda) using mitochondrial DNA (COI) barcodes

Taxonomic and ecological studies of freshwater harpacticoid copepods are limited globally by the ability to easily and accurately identify specimens. Here, we test the use of the mitochondrial cytochrome c oxidase subunit I (COI) gene locus as a tool for assessing the diversity of freshwater Harpacticoida. We obtained sequences from New Zealand harpacticoid copepods, representing two families, five genera and nine species, including the non-indigenous Elaphoidella sewelli. All species were delineated by the COI gene. However, high intraspecific diversity was evident among populations of Elaphoidella bidens (>12%), and between North and South Island populations of Bryocamptus pygmaeus (>18%), potentially indicating the presence of morphologically cryptic taxa. We suggest that mitochondrial DNA (COI) sequences can provide a useful tool for the routine identification of freshwater harpacticoid copepods. Applications of these data will include assessing species diversity and biogeography as well as assisting with the detection of non-indigenous species.