The dark-color inducing neuropeptide, [His(7)]-corazonin,causes a shift in morphometic characteristics towards the gregarious phase in isolated-reared (solitarious) Locusta migratoria

The neurohormone, [His⁷]-corazonin is known to induce dark color in the cuticle and epidermis of Locusta migratoria. In the present study, we examined the effects of this hormone on development and morphometrics in two strains, albino and normal, of this locust under isolated conditions. Injection of [His⁷]-corazonin induced dark color in both strains. In either strain, [His⁷]-corazonin injected at the second and third instars did not affect duration of nymphal development or the number of nymphal instars. The shape of the pronotum was more convex in isolated-reared animals than in crowd-reared ones, and injection of [His⁷]-corazonin caused isolated-reared animals to develop a less convex pronotum in the normal strain injected at a high dose (1 nmol×2) but not in the albino strain injected at a low dose (50 pmol×2). [His⁷]-corazonin injected into isolated-reared nymphs caused a shift in classical morphometric ratios (F/C and E/F; F=length of the hind femur, C=maximum width of the head, E=length of the fore wings) towards values typical for crowd-reared (gregarious) individuals of the two strains. This study demonstrated for the first time that [His⁷]-corazonin affected morphometric characteristics in L. migratoria.     

A comparison of phase-related shifts in behavior and morphometrics of an albino strain,deficient in [His(7)]-corazonin,and a normally colored Locusta migratoria strain

The albino Okinawa strain of Locusta migratoria is deficient in the neurohormone [His⁷]-corazonin. This peptide induces darkening of the cuticle, one of the typical features of gregarious locusts. As part of a broader study on the possible role of [His⁷]-corazonin in phase transition, we explored whether corazonin-deficiency might be associated with differences in behavior and morphometrics between albino and normal phenotypes of L. migratoria. Using a modification of the logistic-regression assay of behavioral phase state previously derived for Schistocerca gregaria, we found that there were strain dependent behavioral differences between crowd-reared nymphs of the albino Okinawa and the normally colored African strain, with no evidence of the albino strain being obligatorily solitarious. However, upon isolation, a shift towards more solitarious behavior occurs in both strains, even more profoundly in the Okinawa albinos. A shift could also be recorded in morphometrics. The conclusion is that the albino strain, although showing some solitarious features even when crowd-reared, is not, as has been suggested, obligatory solitarious and, as a consequence, the complete absence of corazonin is not sufficient to bring about the solitarious state.     

飞蝗变型及体色多型的内分泌控制机理

飞蝗具变型现象,散居型和群居型在形态特征、生理机能、行为及体色等方面存在明显差异。保幼激素已被证实能诱导飞蝗散居型绿色的出现。近年,从飞蝗心侧体成功地分离了一种神经肽——黑化诱导激素([His^7]-corazonin),并用白化型进行检测,证实了其对体色黑化作用的活性。不同时间对飞蝗若虫注射不同剂量的[His^7]-corazonin,能诱导出现除绿色以外的散居型体色,如浅褐色、褐色、赤褐色、黑色等;也能诱导出现群居型的体色,即黑色配以橘黄色的底色。而且,对散居型若虫注射[His^7]-corazonin能诱导其形态向群居型转换。这些研究证实[His^7]-corazonin对飞蝗的变型有着重要的控制作用,但又不是唯一的。     

Degradation profile of [His7]-corazonin in the hemolymph of the desert locust Schistocerca gregaria

Degradation of the neuropeptide [His7]-corazonin, a key hormone in phase transition in locusts was studied using [3H][His7]-corazonin, RP-HPLC and mass spectrometry. After 4h incubation, 50 and 75% of [His7]-corazonin could still be found in hemolymph of gregarious and solitarious Schistocerca gregaria, respectively. Under in vivo conditions the half-life was 30 min. These results are in contrast to many other neuropeptides that usually have half lives of a few minutes. The peptide is cleaved first by an endopeptidase, either just before or after the Tyr residue at position 5. Next, the C-terminal degradation fragments are further degraded by a dipeptidyl-peptidase, whereas the N-terminal fragments are further broken down one amino acid at a time. In addition, [Dopa5][His7]-corazonin was detected. Upon synthesis, this unexpected molecular modification turned out to be biologically active in bringing about cuticular melanization.     

Mass spectrometric analysis of peptides in brain neurosecretory cells and neurohemal organs in the adult blowfly,Protophormia terraenovae

Neuropeptides in neurosecretory cells of the pars intercerebralis (PI) and pars lateralis (PL) in the brain, and those in the corpus cardiacum–hypocerebral ganglion complex (CC-HG) and corpus allatum (CA) were examined by mass spectrometry and immunocytochemistry in adult females of the blowfly, Protophormia terraenovae. By using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and electrospray ionization quadrupole orthogonal acceleration time-of-flight mass spectrometry (ESI-Q-Tof MS) and MS/MS, 4 peptides (including myosuppressin and SIFamide) were detected in the PI, 12 peptides (including [Arg⁷]-corazonin and [Arg⁷]-corazonin^3–11) in the PL, 13 peptides (including myosuppressin, [Arg⁷]-corazonin and [Arg⁷]-corazonin^3–11) in the CC-HG, and 6 peptides in the CA. MALDI-TOF MS analysis of each tissue or organ was made in about 20 flies under diapause-inducing (LD 12:12 at 20 °C) and diapause-averting conditions (LD 18:6 at 25 °C). These molecular ion peaks did not distinctively differ between diapause-inducing and diapause-averting conditions. A peptide with an m/z value at 1395.1 was purified from 240 brains and the 2nd–10th amino acids were sequenced as –YRKPPFNGS–, corresponding to a partial sequence of SIFamide. Only two pairs of somata in the PI were immunoreactive to antisera against SIFamide, which were local neurons widely extending fibers throughout the brain neuropils.     

Syntheses and biological evaluation of analogs of luteinizing hormone-releasing hormone (LH-RH) modified in position 2, 3, 4 or 5

Syntheses by the conventional methods as well as the chemical, physical and biological properties are described of the following analogs of the LH-releasing hormone (LH-RH): [Leu³]-LH-RH, [Phe³]-LH-RH, [Trp²] [His³]-LH-RH, Des-Trp³-LH-RH, Des-His²-[Phe⁵]-LH-RH, [Ala⁴]-LH-RH, [Phe⁵]-LH-RH and [Ala⁴] [Phe⁵]-LH-RH. $\text{In vivo}$ assays showed that [Leu³]-LH-RH did not release LH in doses as high as 5 – 25 μg, having less than 0.0008% of LH-RH activity, while [Phe³]-LH-RH had 0.43% of the LH-RH activity of natural LH-RH. The LH-RH activities of [Trp²] [His³]-LH-RH, Des-Trp³-LH-RH and Des-His²-[Phe⁵]-LH-RH were extremely low. On the other hand, [Ala⁴]-LH-RH, [Phe⁵]-LH-RH and [Ala⁴] [Phe⁵]-LH-RH had significant LH-RH activity. The structure-activity relationship of LH-RH is discussed on the basis of these findings.     

Nociceptin and its natural and specifically‐modified fragments: Structural studies

The vibrational structures of Nociceptin (FQ), its short bioactive fragments, and specifically‐modified [Tyr¹]FQ (1‐6), [His¹]FQ (1‐6), and [His^1,4]FQ (1‐6) fragments were characterized. We showed that in the solid state, all of the aforementioned peptides except FQ adopt mainly turn and disordered secondary structures with a small contribution from an antiparallel β‐sheet conformation. FQ (1‐11), FQ (7‐17) [His¹]FQ (1‐6), and [His^1,4]FQ (1‐6) have an α‐helical backbone arrangement that could also slightly influence their secondary structure. The adsorption behavior of these peptides on a colloidal silver surface in an aqueous solution (pH = ～8.3) was investigated by means of surface‐enhanced Raman scattering (SERS). All of the peptides, excluding FQ (7‐17), chemisorbed on the colloidal silver surfaces through a Phe⁴ residue, which for FQ, FQ (1‐11), FQ (1‐6), [Tyr¹]FQ (1‐6), and [His¹]FQ (1‐6) lies almost flat on this surface, while for FQ (1‐13) and FQ (1‐13)NH₂ adopts a slightly tilted orientation with respect to the surface. The Tyr¹ residue in [Tyr¹]FQ (1‐6) does not interact with the colloidal silver surface, suggesting that the Tyr¹ and Phe⁴ side chains are located on the opposite sides of the peptide backbone, which can be also true for His¹ and Phe⁴ in [His¹]FQ (1‐6). The lone pair of electrons on the oxygen atom of the ionized carbonyl group of FQ (1‐13) and FQ (7‐17) appears to be coordinated to the colloidal silver nanoparticles, whereas in the case of the remaining peptides, it only assists in the adsorption process, similar to the ? NH₂ group. We also showed that upon adsorption, the secondary structure of these peptides is altered. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 1039–1054, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

The Identification of Histidine 712 as a Critical Residue for Constitutive TRPV5 Internalization

The epithelial Ca²⁺ channel TRPV5 constitutes the apical entry gate for Ca²⁺ transport in renal epithelial cells. Ablation of the trpv5 gene in mice leads to a reduced Ca²⁺ reabsorption. TRPV5 is tightly regulated by various calciotropic hormones, associated proteins, and other factors, which mainly affect channel activity via the C terminus. To further identify the role of the C terminus in TRPV5 regulation, we expressed channels harboring C-terminal deletions and studied channel activity by measuring intracellular Ca²⁺ concentration ([Ca²⁺]_i) using fura-2 analysis. Removal of amino acid His⁷¹² elevated the [Ca²⁺]_i, indicating enlarged TRPV5 activity. In addition, substitution of the positively charged His⁷¹² for a negative (H712D) or neutral (H712N) amino acid also stimulated TRPV5 activity. This critical role of His⁷¹² was confirmed by patch clamp analysis, which demonstrates increased Na⁺ and Ca²⁺ currents for TRPV5-H712D. Cell surface biotinylation studies revealed enhanced plasma membrane expression of TRPV5-H712D as compared with wild-type (WT) TRPV5. This elevated plasma membrane presence also was observed with the Ca²⁺-impermeable TRPV5-H712D and TRPV5-WT pore mutants, demonstrating that the elevation is not due to the increased [Ca²⁺]_i. Finally, using an internalization assay, we demonstrated a delayed cell surface retrieval for TRPV5-H712D, likely causing the increase in plasma membrane expression. Together, these results demonstrate that His⁷¹² plays an essential role in plasma membrane regulation of TRPV5 via a constitutive endocytotic mechanism.     

Genetic and hormonal control of melanization in reddish–brown and albino mutants in the desert locust Schistocerca gregaria

The genetic and hormonal control of body colouration is investigated using two recessive genetic mutant strains, the reddish–brown (RB) mutant and an albino mutant, as well as a normal (pigmented) strain of the desert locust Schistocerca gregaria. The colour patterns of the RB nymphs are similar to those of a normal strain, although the intensity of the melanization is weaker in the former. Reciprocal crosses between the RB and albino mutants produce only normal phenotypes in the F₁ generation. In the F₂ generation, the normal, RB and albino phenotypes appear in a ratio of 9 : 3 : 4, indicating that two Mendelian units might determine the appearance of dark body colour and the intensity of melanization, respectively. In other words, at least two steps of regulation might be involved in the expression of body colour. Injections of [His⁷]‐corazonin, a neuropeptide inducing dark colour in this locust, fail to induce dark colour in albino nymphs but show a dose‐dependent darkening in RB nymphs in the range, 10 pmol to 1 nmol. Some RB nymphs become indistinguishable from normal individuals after injection of the peptide. Implantation of corpora cardiaca (CC) taken from RB mutants into other RB individuals induces darkening in the latter and CC from RB, albino and normal strains have similar dark colour‐inducing activity when implanted into albino Locusta migratoria. These results suggest the possibility that the RB mutant gene regulates the intensity of melanization, possibly through controlling the pathway of pigment biosynthesis associated with [His⁷]‐corazonin.     

Khayanolides from African mahogany Khaya senegalensis (Meliaceae): A revision

Five khayanolides (1-O-acetylkhayanolide B 1, khayanolide B 2, khayanolide E 3, 1-O-deacetylkhayanolide E 4, 6-dehydroxylkhayanolide E 5) were isolated from the stem bark of African mahogany Khaya senegalensis (Meliaceae). Their structures and absolute configurations were determined through extensive spectroscopic analyses including MS, NMR, and single-crystal X-ray diffraction experiments. The results established that two previously reported khayanolides, 1α-acetoxy-2β,3α,6,8α,14β-pentahydroxy-[4.2.1^10,30.1^1,4]-tricyclomeliac-7-oate 6 and 1α,2β,3α,6,8α,14β-hexahydroxy-[4.2.1^10,30.1^1,4]-tricyclomeliac-7-oate 7, were, in fact, 1-O-acetylkhayanolide B 1 and khayanolide B 2, and that the two reported phragmalin derivatives, methyl 1α-acetoxy-6,8α,14β,30β-tetrahydroxy-3-oxo-[3.3.1^10,2.1^1,4]-tricyclomeliac-7-oate 8 and methyl 1α,6,8α,14β,30β-pentahydroxy-3-oxo-[3.3.1^10,2.1^1,4]-tricyclomeliac-7-oate 9, were, in fact, khayanolide E 3 and 1-O-deacetylkhayanolide E 4, respectively. Based on the results from this study and consideration of the biogenetic pathway, the methyl 6-hydroxyangolensate in African mahogany K. senegalensis should have a C-6 S configuration while methyl 6-hydroxyangolensate in genuine mahogany Swietenia species should have a C-6 R configuration.     

Quantitative analysis of herbivore-induced cytosolic calcium by using a Cameleon (YC 3.6) calcium sensor in Arabidopsis thaliana

Ca²⁺ is a key player in plant cell responses to biotic and abiotic stress. Owing to the central role of cytosolic Ca²⁺ ([Ca²⁺]_cyt) during early signaling and the need for precise determination of [Ca²⁺]_cyt variations, we used a Cameleon YC 3.6 reporter protein expressed in Arabidopsis thaliana to quantify [Ca²⁺]_cyt variations upon leaf mechanical damage (MD), herbivory by 3rd and 5th instar larvae of Spodoptera littoralis and S. littoralis oral secretions (OS) applied to MD. YC 3.6 allowed a clear distinction between MD and herbivory and discriminated between the two larvae instars. To our knowledge this is the first report of quantitative [Ca²⁺]_cyt determination upon herbivory using a Cameleon calcium sensor.     

Hormonal control of phase-related changes in the number of antennal sensilla in the desert locust, Schistocerca gregaria: possible involvement of [His7]-corazonin

The effect of [His(7)]-corazonin on the abundance of antennal sensilla in the desert locust, Schistocerca gregaria, was investigated to test the hypothesis that injection of this neuropeptide would mimic a crowding effect. Solitarious locusts (reared in isolation) were injected with [His(7)]-corazonin at the 3rd nymphal instar and the numbers of sensilla on the 2nd, 8th and 14th antennal segments in the adult stage were compared with those for oil-injected solitarious controls or un-injected gregarious locusts (reared in group). The numbers of sensilla on these antennal segments were all reduced significantly after [His(7)]-corazonin injection compared with those for oil-injected controls, but similar to the values for gregarious individuals. Among the four major types of olfactory sensilla, coeloconic, trichoid, basiconic type A and basiconic type B, [His(7)]-corazonin injection influenced the abundance of all but the last type. The effect of [His(7)]-corazonin injection varied with the time of injection; the earlier the injection the larger the effects on the abundance of total antennal sensilla on the 8th segment, although the way in which the injection affected the abundance varied with the sensillum type. A hypothesis explaining how crowding affects the abundance of antennal sensilla and other phase-related characteristics through changes in [His(7)]-corazonin concentrations was proposed.     

Effect of [His7]-corazonin on the number of antennal sensilla in Locusta migratoria

Abstract.  Certain types of antennal sensilla are known to be more abundant in solitarious individuals than in gregarious ones in the migratory locust, Locusta migratoria . We tested the hypothesis that injection of a neurohormone, [His⁷]-corazonin, into isolated-reared nymphs of this species mimics the effect of crowding on the frequencies of various types of antennal sensilla. One nmol of the hormone was injected into nymphs on two occasions, on the third days of the second and third stadia, respectively. Upon adult emergence, the numbers of different types of sensilla on the eighth antennal segment were compared with those of oil-injected controls. [His⁷]-corazonin did not influence the numbers of basiconic sensilla type A, basiconic sensilla type B and trichoid sensilla significantly compared to oil-injected controls. However, the number of coeloconic sensilla was reduced significantly by the hormone injections. Because the length of the antennal segment was not affected by the hormone injection, it appears that the hormone influenced the development of coeloconic sensilla. The results support the hypothesis tested and are consistent with the idea that [His⁷]-corazonin plays an important role in the control of phase polymorphism in L. migratoria .     

Corazonin reduces the spinning rate in the silkworm,Bombyx mori

The insect neuropeptide, [Arg⁷]-corazonin was injected into larvae of the silkworm, Bombyx mori to investigate its influence on development and behavior. A single injection of 50 pmol of corazonin into the fourth and fifth instar larvae induced prolongation of the spinning period in all experimental groups except for those injected on day 10 of the fifth instar. The injection also caused a prolongation of the pupal period in some experimental groups, while it had no effect on the timing of larval ecdysis and the length of feeding period of the fifth instar. The spinning period was significantly prolonged even at a low dose of 1 pmol. Both the spinning rate and the rate of increase in hemolymph ecdysteroid level during the spinning stage were reduced by injection of corazonin. However, corazonin injection during days 5-7 of the fifth instar reduced the spinning rate without influencing the ecdysteroid level until the end of day 8, thereafter the rate of increase in hemolymph ecdysteroid level was slower in the corazonin-injected larvae than in the control larvae. Therefore, the suppressed ecdysteroid level observed in the corazonin-injected larvae appears to be a result rather than a cause of the reduced spinning rate. This study is the first published report for the corazonin effect on the behavior in insects.     

Isolation and amino terminal sequence of melanization and reddish coloration hormone (MRCH) from the silkworm,Bombyx mori

Cuticular melanization associated with the gregarious phase of the common armyworm larvae, Leucania separata, is caused by a neurohormone, melanization and reddish coloration hormone (MRCH). Two molecular species of MRCH were isolated from 211,000 heads of adult Bombyx mori with conventional column chromatography and reversed-phase high performance liquid chromatography. As little as 6 ng of purified MRCH elicited marked melanization in the cuticle of an L. separata larva. Automated Edman degradation confirmed 16 residues of N-terminal amino acid sequences of the purified MRCHs; these showed homology with each other.     

Contribution of Residue B5 to the Folding and Function of Insulin and IGF-I: CONSTRAINTS AND FINE-TUNING IN THE EVOLUTION OF A PROTEIN FAMILY*

Proinsulin exhibits a single structure, whereas insulin-like growth factors refold as two disulfide isomers in equilibrium. Native insulin-related growth factor (IGF)-I has canonical cystines (A6—A11, A7–B7, and A20—B19) maintained by IGF-binding proteins; IGF-swap has alternative pairing (A7–A11, A6—B7, and A20—B19) and impaired activity. Studies of mini-domain models suggest that residue B5 (His in insulin and Thr in IGFs) governs the ambiguity or uniqueness of disulfide pairing. Residue B5, a site of mutation in proinsulin causing neonatal diabetes, is thus of broad biophysical interest. Here, we characterize reciprocal B5 substitutions in the two proteins. In insulin, His^B5 → Thr markedly destabilizes the hormone (ΔΔG_u 2.0 ± 0.2 kcal/mol), impairs chain combination, and blocks cellular secretion of proinsulin. The reciprocal IGF-I substitution Thr^B5 → His (residue 4) specifies a unique structure with native ¹H NMR signature. Chemical shifts and nuclear Overhauser effects are similar to those of native IGF-I. Whereas wild-type IGF-I undergoes thiol-catalyzed disulfide exchange to yield IGF-swap, His^B5-IGF-I retains canonical pairing. Chemical denaturation studies indicate that His^B5 does not significantly enhance thermodynamic stability (ΔΔG_u 0.2 ± 0.2 kcal/mol), implying that the substitution favors canonical pairing by destabilizing competing folds. Whereas the activity of Thr^B5-insulin is decreased 5-fold, His^B5-IGF-I exhibits 2-fold increased affinity for the IGF receptor and augmented post-receptor signaling. We propose that conservation of Thr^B5 in IGF-I, rescued from structural ambiguity by IGF-binding proteins, reflects fine-tuning of signal transduction. In contrast, the conservation of His^B5 in insulin highlights its critical role in insulin biosynthesis.     

Antiplasmodial activity study of angiotensin II via Ala scan analogs

Angiotensin II (AII) as well as analog peptides shows antimalarial activity against Plasmodium gallinaceum and Plasmodium falciparum, but the exact mechanism of action is still unknown. This work presents the solid‐phase synthesis and characterization of eight peptides corresponding to the alanine scanning series of AII plus the amide‐capped derivative and the evaluation of the antiplasmodial activity of these peptides against mature P. gallinaceum sporozoites. The Ala screening data indicates that the replacement of either the Ile⁵ or the His⁶ residues causes minor effects on the in vitro antiplasmodial activity compared with AII, i.e. AII (88%), [Ala⁶]‐AII (79%), and [Ala⁵]‐AII (75%). Analogs [Ala³]‐AII, [Ala¹]‐AII, and AII‐NH₂ showed antiplasmodial activity around 65%, whereas the activity of the [Ala⁸]‐AII, [Ala⁷]‐AII, [Ala⁴]‐AII, and [Ala²]‐AII analogs is lower than 45%. Circular dichroism data suggest that AII and the most active analogs adopt a β‐fold conformation in different solutions. All AII analogs, except [Ala⁴]‐AII and [Ala⁸]‐AII, show contractile responses and interact with the AT₁ receptor, [Ala⁵]‐AII and [Ala⁶]‐AII. In conclusion, this approach is helpful to understand the contribution of each amino acid residue to the bioactivity of AII, opening new perspectives toward the design of new sporozoiticidal compounds. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Synthesis and characterization of Mg(II), Mn(II), Zn(II) and Cd(II) complexes with a new heptaaza Schiff base pendant-armed macrocycle: X-ray crystal structure, NMR and computational study

New 2-aminoethyl pendant-armed Schiff base macrocyclic complexes, [ML⁷]²⁺ (M = Mn(II), Mg(II), Zn(II) and Cd(II)), have been prepared via M(II) templated [1 + 1] cyclocondensation of 2,6-diacetylpyridine with a new branched hexamine, N,N,N′,N′-tetrakis(2-aminoethyl)-2,2-dimethylpropane-1,3-diamine. The ligand is a 16-membered pentaaza macrocycle having two 2-aminoethyl pendant arms [L⁷ is 2,14-dimethyl-6,10-bis(2-aminoethyl)-3,6,10,13,19-pentaazabicyclo[13.3.1]8,8-dimethylnonadeca-1(19),2,13,15,17-pentaene]. The crystal structures of [MnL⁷]²⁺ and [MgL⁷]²⁺ were determined from X-ray diffraction data. The geometry of the coordination sphere of complexes is a slightly distorted pentagonal bipyramid with the metal ion located within a pentaaza macrocycle and two pendant amines coordinating on opposite sides. All complexes were characterized by IR, microanalysis and except of [MnL⁷]²⁺ by ¹H NMR, ¹³C NMR, DEPT135, COSY(H, H) and HMQC spectroscopy. The data indicate that the structure is pentagonal bipyramidal in each case. The structure of all complexes has also been theoretically studied by ab initio Hartree-Fock and density functional theory methods.     

Gallium and indium compounds supported by a [PNP] pincer ligand

The new bis(phosphino)amido ligand, [MePNP^Ph], that incorporates (i) an ortho-tolylene linker between nitrogen and phosphorus and (ii) phenyl substituents on phosphorus, has been synthesized as its protonated derivative, [MePNP^Ph]H, via sequential treatment of (2-Br,4-Me-C₆H₃)₂NH with (i) BuⁿLi, (ii) Ph₂PCl and (iii) HCl. Deprotonation of [MePNP^Ph]H with BuⁿLi in THF affords the lithium derivative which has been isolated as both mono and bis THF adducts, [MePNP^Ph]Li(THF) and [MePNP^Ph]Li(THF)₂. Treatment of [MePNP^Ph]Li(THF)₂ with GaCl₃ and InX₃ (X = Cl, Br, I) gives a series of [MePNP^Ph]MX₂ complexes in which the [PNP] donor binds in a “T”-shaped manner and the metal has a distorted trigonal bipyramidal geometry. The reaction of [MePNP^Ph]Li(THF)₂ with “GaI” yields the Ga-Ga bonded complex [κ²-MePNP^Ph](GaI)(GaI)[κ²-MePNP^Ph] in which the [MePNP^Ph] ligand binds in a κ²-P,N manner. The bis(phosphino)amine [MePNP^Ph]H may also serve as a ligand and treatment of [MePNP^Ph]H with GaBr₃ affords [κ²-{[MePNP^Ph]H}GaBr₂][GaBr₄], in which the [MePNP^Ph]H ligand coordinates in a κ²-P,P manner such that the gallium adopts a tetrahedral geometry.     

Behavioural phase change in the Australian plague locust, Chortoicetes terminifera, is triggered by tactile stimulation of the antennae

Density-dependent phase polyphenism is a defining characteristic of the paraphyletic group of acridid grasshoppers known as locusts. The cues and mechanisms associated with crowding that induce behavioural gregarization are best understood in the desert locust, Schistocerca gregaria, and involve a combination of sensory inputs from the head (visual and olfactory) and mechanostimulation of the hind legs, acting via a transient increase in serotonin in the thoracic ganglia. Since behavioural gregarization has apparently arisen independently multiple times within the Acrididae, the important question arises as to whether the same mechanisms have been recruited each time. Here we explored the roles of visual, olfactory and tactile stimulation in the induction of behavioural gregarization in the Australian plague locust, Chortoicetes terminifera. We show that the primary gregarizing input is tactile stimulation of the antennae, with no evidence for an effect of visual and olfactory stimulation or tactile stimulation of the hind legs. Our results show that convergent behavioural responses to crowding have evolved employing different sites of sensory input in the Australian plague locust and the desert locust.