<Emphasis Type="Italic">Aphidius ervi</Emphasis> Preferentially Attacks the Green Morph of the Pea Aphid, <Emphasis Type="Italic">Acyrthosiphon pisum</Emphasis>

The pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae) is found in red and green color morphs. Previous work has suggested that the aphidiine parasitoid Aphidius ervi Haliday preferentially attacks green pea aphids in the field. It is not clear whether these results reflect a real preference, or some unknown clonal difference, such as in immunity, between the aphids used in the previous studies. We used three susceptibility-matched pairs of red and green morph pea aphid clones to test for preferences. In a no-choice situation, the parasitoids attacked equal proportions of each color morph. When provided with a choice, A. ervi was significantly more likely to oviposit into colonies formed from green morphs when the neighboring colony was formed from red morph aphids. In contrast, red morphs were less likely to be attacked when their neighboring colony was of the green morph. By preferentially attacking green colonies, A. ervi may reduce the likelihood of intraguild predation, as it is suggested that visually foraging predators preferentially attack red aphid colonies. Furthermore, if this host choice behavior is replicated in the field, we speculate that color morphs of the pea aphid may interact indirectly through their shared natural enemies, leading to intraspecific apparent competition.     

Gene knockdown by RNAi in the pea aphid <Emphasis Type="Italic">Acyrthosiphon pisum</Emphasis>

Background  

RNA interference (RNAi) is a powerful method to inhibit gene expression in a sequence specific manner.     

Floral development and systematic position of <Emphasis Type="Italic">Arillastrum</Emphasis>, <Emphasis Type="Italic">Allosyncarpia</Emphasis>, <Emphasis Type="Italic">Stockwellia</Emphasis> and <Emphasis Type="Italic">Eucalyptopsis</Emphasis> (Myrtaceae)

We have investigated the floral ontogeny of Arillastrum, Allosyncarpia, Stockwellia and Eucalyptopsis (of the eucalypt group, Myrtaceae) using scanning electron microscopy and light microscopy. Several critical characters for establishing relationships between these genera and to the eucalypts have been determined. The absence of compound petaline primordia in Arillastrum, Allosyncarpia, Stockwellia and Eucalyptopsis excludes these taxa from the eucalypt clade. Post-anthesis circumscissile abscission of the hypanthium above the ovary in Stockwellia, Eucalyptopsis and Allosyncarpia is evidence that these three taxa form a monophyletic group; undifferentiated perianth parts and elongated fusiform buds are characters that unite Stockwellia and Eucalyptopsis as sister taxa. No floral characters clearly associate Arillastrum with either the eucalypt clade or the clade of Stockwellia, Eucalyptopsis and Allosyncarpia.We gratefully acknowledge Clyde Dunlop and Bob Harwood (Northern Territory Herbarium) for collecting specimens of Allosyncarpia, and Bruce Gray (Atherton) for collecting specimens of Stockwellia. The Australian National Herbarium (CANB) kindly lent herbarium specimens of Eucalyptopsis for examination. This research was supported by a University of Melbourne Research Development Grant to Andrew Drinnan.     

The <Emphasis Type="Italic">Caenorhabditis</Emphasis><Emphasis Type="Italic">briggsae</Emphasis> genome contains active <Emphasis Type="Italic">CbmaT1</Emphasis> and <Emphasis Type="Italic">Tcb1</Emphasis> transposons

The maT clade of transposons is a group of transposable elements intermediate in sequence and predicted protein structure to mariner and Tc transposons, with a distribution thus far limited to a few invertebrate species. We present evidence, based on searches of publicly available databases, that the nematode Caenorhabditis briggsae has several maT-like transposons, which we have designated as CbmaT elements, dispersed throughout its genome. We also describe two additional transposon sequences that probably share their evolutionary history with the CbmaT transposons. One resembles a fold back variant of a CbmaT element, with long (380-bp) inverted terminal repeats (ITRs) that show a high degree (71%) of identity to CbmaT1. The other, which shares only the 26-bp ITR sequences with one of the CbmaT variants, is present in eight nearly identical copies, but does not have a transposase gene and may therefore be cross mobilised by a CbmaT transposase. Using PCR-based mobility assays, we show that CbmaT1 transposons are capable of excising from the C. briggsae genome. CbmaT1 excised approximately 500 times less frequently than Tcb1 in the reference strain AF16, but both CbmaT1 and Tcb1 excised at extremely high frequencies in the HK105 strain. The HK105 strain also exhibited a high frequency of spontaneous induction of unc-22 mutants, suggesting that it may be a mutator strain of C. briggsae.     

Regulation of stipule development by <Emphasis Type="Italic">COCHLEATA</Emphasis> and <Emphasis Type="Italic">STIPULE</Emphasis>-<Emphasis Type="Italic">REDUCED</Emphasis> genes in pea <Emphasis Type="Italic">Pisum sativum</Emphasis>

Pisum sativum L., the garden pea crop plant, is serving as the unique model for genetic analyses of morphogenetic development of stipule, the lateral organ formed on either side of the junction of leafblade petiole and stem at nodes. The stipule reduced (st) and cochleata (coch) stipule mutations and afila (af), tendril-less (tl), multifoliate-pinna (mfp) and unifoliata-tendrilled acacia (uni-tac) leafblade mutations were variously combined and the recombinant genotypes were quantitatively phenotyped for stipule morphology at both vegetative and reproductive nodes. The observations suggest a role of master regulator to COCH in stipule development. COCH is essential for initiation, growth and development of stipule, represses the UNI-TAC, AF, TL and MFP led leafblade-like morphogenetic pathway for compound stipule and together with ST mediates the developmental pathway for peltate-shaped simple wild-type stipule. It is also shown that stipule is an autonomous lateral organ, like a leafblade and secondary inflorescence.     

Isolation and characterization of the <Emphasis Type="Italic">Larix gmelinii </Emphasis><Emphasis Type="Italic">ANGUSTIFOLIA</Emphasis> (<Emphasis Type="Italic">LgAN</Emphasis>) gene

ANGUSTIFOLIA (AN), a plant homolog of C-terminal binding protein, controls the polar elongation of leaf cells and the trichome-branching pattern in Arabidopsis thaliana. In the present study, degenerate PCR was used to isolate an ortholog of AN, referred to as LgAN, from larch (Larix gmelinii). The LgAN cDNA is predicted to encode a protein of 646 amino acids that shows striking sequence similarity to AN proteins from other plants. The predicted amino acid sequence has a conserved NAD-dependent 2-hydroxy acid dehydrogenase (D2-HDH) motif and a plant AN-specific LxCxE/D motif at its N-terminus, as well as a plant-specific long C-terminal region. The LgAN gene is a single-copy gene that is expressed in all larch tissues. Expression of the LgAN cDNA rescued the leaf width and trichome-branching pattern defects in the angustifolia-1 (an-1) mutant of Arabidopsis, showing that the LgAN gene has effects complementary to those of AN. These results suggest that the LgAN gene has the same function as the AN gene.     

Juvenile hormone effects on polymorphism in the pea aphid, Acyrthosiphon pisum

When reared in short days (LD 12:12) at 15°C, apterous Acyrthosiphon pisum gave birth to sexual females (oviparae) exclusively for the first eight days of larviposition. After this time they switched to the production of parthenogenetic females (viviparae). Topical application of juvenile hormones I, II and III to fourth instar or adult ovipara-producers induced the precocious appearance of parthenogenetic females in the progeny sequence. Various forms intermediate between oviparae and viviparae were also produced and repetitive JH-I treatments resulted in a few alatiform progeny. However, many of the JH induced apterous, parthenogenetic females appeared to be normal viviparae and were capble of reproduction. Thus, prenatal treatment of oviparous embryos with JH diverts development towards the viviparous form. JH-I treatment of long-day reared A. pisum had no effect on the type of progeny produced.

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Effets de l'hormone juvénile sur le polymorphisme d'Acythosiphon pisum

Résumé Quand il est élevé sous jours courts (LN 12/12) à 15°C, le type anglais vert d'Acyrthosiphon pisum ne donne naissance qu'à des femelles sexuées (ovipares) pendant la première partie de sa période de reproduction. Ensuite quelques types intermédiaires ovipares/vivipares peuvent apparaitre avant que les pucerons ne bifurquent spontanément vers la production de femelles parthénogénétiques (vivipares). L'application cutanée d'hormones juvéniles (JH I, II, et III) aux larves de quatrième stade ou à des adultes producteurs d'ovipares provoque l'apparition prématurée d'intermédiaires et de vivipares dans la descendance. Les différentes formes intermédiaires produites par des applications répétées de J.H. comprenaient des types ailés ou partiellement ailés. Cependant, les vivipares aptères induits par J.H. étaient morphologiquement normaux et beaucoup étaient capables de se reproduire. Des traitements semblables aux J.H. de vivipares élevées en jours longs (LN 16/8) n'ont pas eu d'effets sur le type de la descendance.On ne sait pas si l'action de JH exogène sur l'induction des vivipares est direct ou indirect. La reprogrammation des embryons, autrement destinés à se développer comme ovipares, est examinée en relation avec notre connaissance du contrôle endocrine du polymorphisme des pucerons.

     

<Emphasis Type="Italic">Funastrum rupicola</Emphasis> (<Emphasis Type="Italic">Apocynaceae:</Emphasis><Emphasis Type="Italic">Asclepiadoideae</Emphasis>), a new species from Bolivia

Summary   Funastrum rupicola Goyder, a new species of Apocynaceae: Asclepiadoideae from Bolivia, is described and illustrated. The conservation status of this species is assessed.     

<Emphasis Type="Italic">Phuphanochloa,</Emphasis> a new bamboo genus (<Emphasis Type="Italic">Poaceae</Emphasis>: <Emphasis Type="Italic">Bambusoideae</Emphasis>) from Thailand

Summary  A new monotypic bamboo genus Phuphanochloa (Poaceae: Bambusoideae) from north-eastern Thailand is described, together with a new species, P. speciosa.     

<Emphasis Type="Italic">Drosophila</Emphasis><Emphasis Type="Italic">P</Emphasis> transposons of the urochordata <Emphasis Type="Italic">Ciona intestinalis</Emphasis>

P transposons belong to the eukaryotic DNA transposons, which are transposed by a cut and paste mechanism using a P-element-coded transposase. They have been detected in Drosophila, and reside as single copies and stable homologous sequences in many vertebrate species. We present the P elements Pcin1, Pcin2 and Pcin3 from Ciona intestinalis, a species of the most primitive chordates, and compare them with those from Ciona savignyi. They showed typical DNA transposon structures, namely terminal inverted repeats and target site duplications. The coding region of Pcin1 consisted of 13 small exons that could be translated into a P-transposon-homologous protein. C. intestinalis and C. savignyi displayed nearly the same phenotype. However, their P elements were highly divergent and the assumed P transposase from C. intestinalis was more closely related to the transposase from Drosophila melanogaster than to the transposase of C. savignyi. The present study showed that P elements with typical features of transposable DNA elements may be found already at the base of the chordate lineage. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Influence of <Emphasis Type="Italic">Lecanicillium attenuatum</Emphasis> on the development and reproduction of the cotton aphid, <Emphasis Type="Italic">Aphis gossypii</Emphasis>

The activity of entomopathogens on insect pests has been investigated for many species but the influence of entomopathogenic fungi on factors other than mortality relating to population increase has not been frequently studied. The influence of Lecanicillium attenuatum CS625 (=Verticillium lecanii CS625) on development and reproduction of cotton aphid (Aphis gossypii) was investigated. A conidia suspension of the isolate was applied onto first instar nymphs. Increased spore concentration did not significantly affect each nymphal stage, total nymphal period, pre-reproductive period and the age of first larviposition. A significant dose effect on reduction of life span, reproductive period and fecundity was observed in 1st and 3rd instars after spore application. When conidia were applied to 1st instars, life span was significantly reduced to 10.8 and 8.4 days at 1 × 10⁴ and 1 × 10⁸ conidia/ml, respectively from 12.2 days in the control. During the life span, total fecundity was 41 ± 7.3, 26 ± 0.8 and 22 ± 5.7 nymphs per female at 1 × 10⁴, 1 × 10⁶ and 1 × 10⁸ conidia/ml, respectively compared with 51 ± 2.0 nymphs per untreated female. Reproduction period was also significantly shortened with increasing spore concentration. Application of spores to 3rd instars showed a similar trend. However, daily fecundity of individual aphids was not affected by spore dose. It was concluded that the isolate of L. attenuatum is able to affect populations of cotton aphid by reducing life span and total fecundity as well as by killing the aphids directly.     

The transformation of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.): applicable methods of <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated gene transfer

Three methods of transformation of pea (Pisum sativum ssp. sativum L. var. medullare) were tested. The most efficient Agrobacterium tumefaciens-mediated T-DNA transfer was obtained using embryonic segments from mature pea seeds as initial explants. The transformation procedure was based on the transfer of the T-DNA region with the reporter gene uidA and selection gene bar. The expression of β-glucuronidase (GUS) in the regenerated shoots was tested using the histochemical method and the shoots were selected on a medium containing phosphinothricin (PPT). The shoots of putative transformants were rooted and transferred to non-sterile conditions. Transient expression of the uidA gene in the tissues after co-cultivation and in the course of short-term shoot cultivation (confirmed by histochemical analysis of GUS and by RT-PCR of mRNA) was achieved; however, we have not yet succeeded in proving stable incorporation of the transgene in the analysed plants.     

A new species of <Emphasis Type="Italic">Macroptilium</Emphasis> (Benth.) Urb. (<Emphasis Type="Italic">Leguminosae</Emphasis>: <Emphasis Type="Italic">Papilionoideae</Emphasis>: <Emphasis Type="Italic">Phaseolinae</Emphasis>) from North-Eastern Brazil

Summary  A new species of Macroptilium sect. Microcochle (Benth.) J. A. Lackey is herein described from the states of Piauí and Bahia, Brazil. Macroptilium cochleatum is characterized by few-flowered inflorescences, calyx teeth longer than the tube, a tightly four-coiled keel, and linear, patent fruits. The discovery of this unique Macroptilium species, with its distally coiled keel, expands the diagnostic features of the genus. A key to the Brazilian species of sect. Microcochle is provided.     

The Madagascan genus <Emphasis Type="Italic">Vaughania</Emphasis> is reduced to synonymy under <Emphasis Type="Italic">Indigofera</Emphasis> (<Emphasis Type="Italic">Leguminosae-Papilionoideae-Indigofereae</Emphasis>)

Summary  Eleven species comprising the Madagascan genus Vaughania are subsumed within the large pantropical genus Indigofera. Six new combinations are made; the remaining species were originally described in Indigofera.     

In planta transformation of <Emphasis Type="Italic">Notocactus scopa</Emphasis> cv. <Emphasis Type="Italic">Soonjung</Emphasis> by <Emphasis Type="Italic">Agrobacterium </Emphasis><Emphasis Type="Italic">tumefaciens</Emphasis>

Notocactus scopa cv. Soonjung was subjected to in planta Agrobacterium tumefaciens-mediated transformation with vacuum infiltration, pin-pricking, and a combination of the two methods. The pin-pricking combined with vacuum infiltration (20-30 cmHg for 15 min) resulted in a transformation efficiency of 67-100%, and the expression of the uidA and nptII genes was detected in transformed cactus. The established in planta transformation technique generated a transgenic cactus with higher transformation efficiency, shortened selection process, and stable gene expression via asexual reproduction. All of the results showed that the in planta transformation method utilized in the current study provided an efficient and time-saving procedure for the delivery of genes into the cactus genome, and that this technique can be applied to other asexually reproducing succulent plant species.     

Morphological and histological examination of polyphenic wing formation in the pea aphid <Emphasis Type="Italic">Acyrthosiphon pisum</Emphasis> (Hemiptera,Hexapoda)

Aphids display divergent adult phenotypes, depending on environmental conditions experienced during their embyonic and nymphal stages in their complex life cycles. The plastic developmental mode is an extreme case of phenotypic plasticity, so-called “polyphenism”, in which discrete multiple phenotypes are produced based on a single genome. For example, winged and wingless adult females are derived from a single genotype. However, the developmental mechanisms producing these polyphenic traits according to the extrinsic stimuli, such as density conditions, still remain unknown. In this study, to analyze the developmental processes underlying the wing polyphenism, we extensively observed and compared wing development in the winged and wingless individuals in parthenogenetic generations of the aphid Acyrthosiphon pisum (Harris), using scanning electron microscopy and histological sectioning. At the first-instar stage, the wing primordia were observed both in the future winged (W) and wingless (WL) nymphs. Developmental differences can be seen from the second-instar stage, when wing primordia degenerate in the WL nymphs, while they develop and become more thickened in the W nymphs, suggesting that the developmental programs should be launched prior to this stage. Furthermore, during the third- to fifth-instar stages, wing buds and flight muscles were well developed in the W nymphs, while wing primordia completely disappeared in the WL ones. In addition, the observation on the detailed developmental process of wing primordia during the third-instar W nymphs showed that the wing buds become swollen especially at the basal part, even during the intermolt period. This was caused by the development of wing epithelia under the cuticle of this instar nymph. Actually on the surface of the cuticle of wing-bud bases, there were numerous furrows, which gradually expand during the intermolt period. The similar situation was also observed at the forth-instar nymphs, in which the wings are formed in the complicated manner inside the wing pads. Furthermore, the developmental process of flight muscles was also described in detail. These dynamic developmental differences between the wing morphs should be regulated under the gene expression cascades that switch according to environmental stimuli.