Identification and functional characterization of the Arabidopsis Snf1‐related protein kinase SnRK2.4 phosphatidic acid‐binding domain

Phosphatidic acid (PA) is an important signalling lipid involved in various stress‐induced signalling cascades. Two SnRK2 protein kinases (SnRK2.4 and SnRK2.10), previously identified as PA‐binding proteins, are shown here to prefer binding to PA over other anionic phospholipids and to associate with cellular membranes in response to salt stress in Arabidopsis roots. A 42 amino acid sequence was identified as the primary PA‐binding domain (PABD) of SnRK2.4. Unlike the full‐length SnRK2.4, neither the PABD‐YFP fusion protein nor the SnRK2.10 re‐localized into punctate structures upon salt stress treatment, showing that additional domains of the SnRK2.4 protein are required for its re‐localization during salt stress. Within the PABD, five basic amino acids, conserved in class 1 SnRK2s, were found to be necessary for PA binding. Remarkably, plants overexpressing the PABD, but not a non‐PA‐binding mutant version, showed a severe reduction in root growth. Together, this study biochemically characterizes the PA–SnRK2.4 interaction and shows that functionality of the SnRK2.4 PABD affects root development.     

Differences in intestinal microbiota between avian brood parasites and their hosts

The intestinal microbiota determines the effectiveness of digestion in vertebrates, and is influenced by the external environment (mainly the diet), gut characteristics, and phylogeny. Avian brood-parasitic nestlings of the sub-family Cuculinae develop in nests of phylogenetically distant passerines and can be fed with the host diet. If the shaping of bacterial communities is dominated by phylogenetic constraints, and therefore the microbiota of parasitic nestlings differs from that of host nestlings, the energy and micronutrients that parasites and hosts obtain from a similar amount of food would be different. In this case, the bacterial communities of parasitic and host nestlings would have important consequences with respect to brood parasite development. By experimentally creating mixed broods of magpies ( Pica pica ) and great spotted cuckoos ( Clamator glandarius ), we investigated their cloacal microbiota using ribosomal intergenic spacer analysis. We found significant differences in bacterial assemblages of the parasitic and host nestlings, although none of the phylotypes were specific in either great spotted cuckoos or magpies. Cuckoos presented more complex communities, which could help the brood parasitic life style and allow the digestion of food provided by different potential hosts. Moreover, the intestinal morphology is different between the two species due to phylogenetic differences in the two taxa, which would influence the dissimilar bacterial assemblages. The detected differences in microbiota of great spotted cuckoo and magpie nestlings, which might occur in other brood parasite–host systems, may imply a lower digestion efficiency in parasites. Thus, the higher level requirements of cuckoo nestlings may be explained, at least in part, by cuckoos having a suboptimal bacterial community for processing the host diet.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 406–414.     

Mobilization of Reserves and Synthesis of Sterols and Triterpenes in Seedlings of Two Canarian Euphorbia Species

Seedlings from Euphorbia canariensis and Euphorbia lambii weregrown in the dark at 25 °C. Protein and triglyceride contentas well as levels of sugars and amino acids in the endospermwere determined during endosperm depletion. In the endospermof Euphorbia canariensis, relatively low levels of amino acids(up to 1 µmol.endosperm^–1) were found of which glutamine/glutamateaccounted for 40% at the stage of radicle emergence. High levelsof amino acids (up to 4 µmol.endosperm^–1) comparedwith sugars (up to 2 µmol sucrose.endosperm^–1) weredetected in the endosperm of Euphorbia lambii. Arginine wasthe main component (28 µmol%) of the amino acids in thistissue. In both species amino acid composition changed graduallyduring endosperm depletion. Cotyledons retained their ability to absorb a variety of watersoluble substrates after removal of the endosperm. ¹⁴C from[U-¹⁴C]sucrose was effectively incorporated into the triterpenesof the laticifers and to a lesser extent into the sterols ofthe seedling. The highest incorporation values were found inyoung seedlings about 2 d after the emergence of the radicle.Seedlings of this age also showed high incorporation rates of¹⁴C from labelled alanine, serine, threonine, valine, leucineand isoleucine into both triterpenols and sterols, but no generalconclusions about metabolic channelling in lipid synthesis couldbe made. Endosperm, Euphorbia canariensis L. Euphorbia lambii Svent., sterols, triterpenols, amino acids, laticifer, biosynthesis     

Performance of Myrmica ant colonies is correlated with the presence of social parasites

1. The performance of ant colonies depends on different factors such as nest site, colony structure or the presence of pathogens and social parasites. Myrmica ants host various types of social parasites, including the larvae of Maculinea butterflies and Microdonmyrmicae (Schönrogge) hoverfly. How these social parasites affect host colony performance is still unexplored. 2. It was examined how the presence of Maculinea teleius Bergsträsser, Maculinea alcon (Denis & Schiffermüller), and M. myrmicae larvae, representing different feeding and growth strategies inside host colonies, is associated with worker survival, the number of foragers, and colony productivity parameters such as growth and reproduction. 3. It was found that the presence of social parasites is negatively associated with total colony production and the production of ant larvae and gynes. Male production was lower only in nests infested by M. teleius, whereas the number of worker pupae was significantly higher in all types of infested colonies than in uninfested colonies. Laboratory observations indicated that nests infested by Maculinea larvae are characterised by a higher number of foragers compared to uninfested nests but we did not find differences in worker survival among nest types. 4. The observed pattern of social parasite influence on colony productivity can be explained by the feeding strategies of parasitic larvae. The most negative effect was found for M. teleius, which feeds on the largest host brood and eliminates a high number of sexual forms. The strong, adverse influence of all studied parasite species on gyne production may result in low queen production in Myrmica populations exposed to these social parasites.