Divergent RNA localisation patterns of maternal genes regulating embryonic patterning in the butterfly Pararge aegeria

The maternal effect genes responsible for patterning the embryo along the antero-posterior(AP) axis are broadly conserved in insects. The precise function of these maternal effect genes is the result of the localisation of their mRNA in the oocyte. The main developmental mechanisms involved have been elucidated in Drosophila melanogaster, but recent studies have shown that other insect orders often diverge in RNA localisation patterns. A recent study has shown that in the butterfly Pararge aegeria the distinction between blastodermal embryonic (i.e. germ band) and extra-embryonic tissue (i.e. serosa) is already specified in the oocyte during oogenesis in the ovariole, long before blastoderm cellularisation. To examine the extent by which a female butterfly specifies and patterns the AP axis within the region fated to be the germ band, and whether she specifies a germ plasm, we performed in situ hybridisation experiments on oocytes in P. aegeria ovarioles and on early embryos. RNA localisation of the following key maternal effect genes were investigated: caudal (cad),orthodenticle (otd), hunchback (hb) and four nanos (nos) paralogs, as well as TDRD7 a gene containing a key functional domain (OST-HTH/LOTUS) shared with oskar. TDRD7 was mainly confined to the follicle cells, whilst hb was exclusively zygotically transcribed. RNA of some of the nos paralogs, otd and cad revealed complex localisation patterns within the cortical region prefiguring the germ band (i.e. germ cortex). Rather interestingly, otd was localised within and outside the anterior of the germ cortex. Transcripts of nos-O formed a distinct granular ring in the middle of the germ cortex possibly prefiguring the region where germline stem cells form. These butterfly RNA localisation patterns are highly divergent with respect to other insects, highlighting the diverse ways in which different insect orders maternally regulate early embryogenesis of their offspring

Development on drought-stressed host plants affects life history, flight morphology and reproductive output relative to landscape structure

With global climate change, rainfall is becoming more variable. Predicting the responses of species to changing rainfall levels is difficult because, for example in herbivorous species, these effects may be mediated indirectly through changes in host plant quality. Furthermore, species responses may result from a simultaneous interaction between rainfall levels and other environmental variables such as anthropogenic land use or habitat quality. In this eco-evolutionary study, we examined how male and female Pararge aegeria (L.) from woodland and agricultural landscape populations were affected by the development on drought-stressed host plants. Compared with individuals from woodland landscapes, when reared on drought-stressed plants agricultural individuals had longer development times, reduced survival rates and lower adult body masses. Across both landscape types, growth on drought-stressed plants resulted in males and females with low forewing aspect ratios and in females with lower wing loading and reduced fecundity. Development on drought-stressed plants also had a landscape-specific effect on reproductive output; agricultural females laid eggs that had a significantly lower hatching success. Overall, our results highlight several potential mechanisms by which low water availability, via changes in host plant quality, may differentially influence P. aegeria populations relative to landscape structure

The Chichibabin amination of diazines geometrical isomerism in anions of aromatic amines

The first part of this thesis describes investigations into the mechanistic aspects of the Chichibabin amination of some diazines in liquid ammonia containing potassium amide.The nucleophilic attack of the amide ion on 4-phenylpyrimidine readily takes place at C-2, due to its low electron density, and at C-6 because of the thermodynamic stability of the resulting σ-adduct. The former kinetically determined C-2 adduct isomerizes into the latter as shown by NMR spectros copy. Both adducts, but no analogous isomerization are observed in 4- t -butyl-pyrimidine. In 5-phenylpyrimidine an adduct on C-2 is not formed.Phenylpyrazine initially undergoes nucleophilic addition in KNH 2 /NH 3 at all three unsubstituted pyrazine carbon atoms. The C-5 adduct is thermodynamically. the most stable one.Amination of 4-phenylpyrimidine in 15N-labeled KNH 2 /NH 3 clearly shows that a ring opening-ring closure sequence (the S N (ANRORC) mechanism) must be in volved in the formation of the main product 2-amino-4- phenylpyrimidine. Quenching of the reaction with ammonium salt is an essential requirement for this mechanism. The conclusion is that the intermediate 6-amino-1,6-dihydro-4-phenylpyrimidine undergoes the ring opening. In the amination of 5-phenylpyrimidine the product 2-amino-5-phenylpyrimidine is also formed via an acyclic intermediate. In contrast, 4- t -butylpyrimidine, pyrazine and phenyl-pyrazine do not follow this S N (ANRORC) mechanism.The second part of this thesis deals with the occurrence of geometrical isomerism in the anions of aromatic amino compounds. NMR spectroscopy reveals the presence of two isomers of azaaromatic amines in liquid ammonia containing potassium amide, and even of anilines, in which the rotational barrier is lower. Coalescence is observed on increasing the temperature.The 1H and 13C NMR spectra are assigned to the syn - and anti -isomers. In all anions the ortho -hydrogen atom in the syn position relative to the lone pair of the exocyclic nitrogen atom resonates at lower field than in the anti position.In contrast, the ortho13C atoms do not show such a straightforward rela tionship in the anions of amino- as well as (methylamino)pyridines. In the former ions the signal of the ortho -carbon in the syn position relative to the nitrogen lone pair is found at higher field than in the anti position, whereas in the (methylamino)pyridine anions this signal is observed at lower field.With these data it is shown that the presence of a methyl substituent ortho to the amino group in aminopyridine anions causes a preference for the iso mer in which the amino hydrogen and the methyl group are directed towards each other. The conclusion is that the effective size of the lone pair is larger than that of an amino hydrogen, probably due to solvation. Stabilization of the preferred isomer by other effects, however, cannot be excluded

Resonances and higher twist in polarized lepton-nucleon scattering

We present a detailed analysis of resonance contributions in the context of higher twist effects in the moments of the proton spin structure function g_1. For each of these moments, it is found that there exists a characteristic Q^2 region in which (perturbative) higher twist corrections coexist with (non-perturbative) resonance contribution of comparable magnitude.Comment: 17 pages LaTe

Seasonal environments drive convergent evolution of a faster pace-of-life in tropical butterflies

New ecological niches that may arise due to climate change can trigger diversification, but their colonisation often requires adaptations in a suite of life-history traits. We test this hypothesis in species-rich Mycalesina butterflies that have undergone parallel radiations in Africa, Asia, and Madagascar. First, our ancestral state reconstruction of habitat preference, using c. 85% of extant species, revealed that early forest-linked lineages began to invade seasonal savannahs during the late Miocene-Pliocene. Second, rearing replicate pairs of forest and savannah species from the African and Malagasy radiation in a common garden experiment, and utilising published data from the Asian radiation, demonstrated that savannah species consistently develop faster, have smaller bodies, higher fecundity with an earlier investment in reproduction, and reduced longevity, compared to forest species across all three radiations. We argue that time-constraints for reproduction favoured the evolution of a faster pace-of-life in savannah species that facilitated their persistence in seasonal habitats.Peer reviewe

Activated Ion Electron Capture Dissociation (AI ECD) of proteins: synchronization of infrared and electron irradiation with ion magnetron motion.

Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a CO(2) laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion. This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides (tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and measured on the time scale longer than the period of ion magnetron motion