Analysis of metabolites in the terpenoid pathway of Catharanthus roseus cell suspensions

In Catharanthus roseus cell cultures, the monoterpenoid pathway has been shown to be a limiting factor in terpenoid indole alkaloid (TIA) production. This could be due to competition at the level of isopentenyl diphosphate::dimethylallyl diphosphate (C5) which leads to the biosynthesis of different terpenoid groups. For future engineering of the terpenoid pathway, chemical characterization of C. roseus cell cultures is a necessity. Therefore, in this study nine C. roseus cell suspension lines were characterized by analyzing the levels of the major terpenoids derived from different biosynthetic pathways which may compete for the same precursors; TIA (monoterpenoid, C10), carotenoids (tetraterpenoid, C40), and sterols (triterpenoid, C30). Among the cell lines, CRPP (S) was the most promising TIA-producing cell line which provided more TIA [24 μmol g^?1 dry weight (DW)] than carotenoids (15 μmol g^?1 DW) and sterols (2 μmol g^?1 DW). However, when considering the distribution of the isopentenyl-precursor (C5), the carotenoids which assemble from 8× C5 represent twofold more C5-units (122 μmol g^?1 DW) than the TIA in this cell line. In the CRPP (G), A12A2 (G), and A12A2 (S) cell lines, the C5 distribution was predominant toward carotenoid biosynthesis as well, resulting in a relatively high accumulation of carotenoids. The geranylgeranyl diphosphate (C20) pathway toward carotenoid production is therefore considered competitive toward TIA biosynthesis. For channeling more precursors to the TIA, the branch point for C10 and C20 seems an interesting target for metabolic engineering. Using principal component analysis of the chromatographic data, we characterized the cell lines chemically based on their metabolite levels. The information on the metabolic composition of C. roseus cell cultures is useful for developing strategies to engineer the metabolic pathways and for selection of cell lines for future studies.     

Time Space Translation: A Hox Mechanism for Vertebrate A-P Patterning

The vertebrate A-P axis is a time axis. The head is made first and more and more posterior levels are made at later and later stages. This is different to the situation in most other animals, for example, in Drosophila. Central to this timing is Hox temporal collinearity (see below). This occurs rarely in the animal kingdom but is characteristic of vertebrates and is used to generate the primary axial Hox pattern using time space translation and to integrate successive derived patterns (see below). This is thus a different situation than in Drosophila, where the primary pattern guiding Hox spatial collinearity is generated externally, by the gap and segmentation genes.     

NITPICK: peak identification for mass spectrometry data

Background  

The reliable extraction of features from mass spectra is a fundamental step in the automated analysis of proteomic mass spectrometry (MS) experiments.     

PA,a stress-induced short cut to switch-on ethylene signalling by switching-off CTR1?

Constitutive triple response 1 (CTR1) is a protein kinase that represses plant responses to ethylene. Recently, we have shown that CTR1 function is negatively regulated by the lipid second messenger phosphatidic acid (PA) in vitro.¹ PA was shown to inhibit (1) CTR1''s protein kinase activity, (2) the intramolecular interaction between N-terminus and kinase domain, and (3) the interaction of CTR1 with the ethylene receptor ETR1. PA typically accumulates within minutes in response to biotic or abiotic stresses, which are known to induce ethylene formation. Although long-term treatment with ethephon does stimulate PA accumulation, our results show no fast increase in PA in response to ethylene. A speculative model is presented which explains how stress-induced PA formation could switch on downstream ethylene responses via interaction of the lipid with CTR1.Key words: lipid signaling, phosphatidic acid, ethylene, constitutive triple response 1, plant stress signaling, protein kinase, phospholipase D     

The utility of the morphological variation of pollen for resolving the evolutionary history of Billia (subfam. Hippocastanoideae,Sapindaceae)

In this study, we examined the utility of pollen morphology for resolving questions about the evolutionary history of Billia, which is a poorly known genus of Neotropical trees. Billia has been traditionally circumscribed with two species and treated as sister to Aesculus L. However, the number of species in Billia is uncertain, because the genus exhibits abundant morphological diversity but little discontinuous variation. Therefore, Billia may be monotypic and highly polymorphic, or it may have two species with blurred boundaries due to incipient speciation and/or hybridization. Moreover, one recent molecular phylogenetic study shows Billia nested withinAesculus. Our work sought to address the following questions: (i) Are there discontinuities in the pollen of Billia that may suggest species boundaries? (ii) Does the pollen of Billia show evidence for inter-specific hybridization? (iii) Do the exine morphology and size of pollen in Billia differ from those in Aesculus? Our results from scanning electron microscopy showed that pollen exine morphology is not taxonomically informative in Billia but that there are significant differences in pollen size between red- and white-flowered individuals. Thus, our pollen data support the utility of flower color in Billia for species delimitation. Our assessments of pollen viability do not support hybridization in the genus, but cannot be used to rule it out. Finally, pollen exine morphology may lend some support to an evolutionary origin ofBillia within eastern North American Aesculus. In contrast, data on pollen size suggest that Billia may belong in a topological position outside of Aesculus.