Accumulation and decay of DG42 gene products follow a gradient pattern during Xenopus embryogenesis

The DG42 gene is expressed during a short window during embryogenesis of Xenopus laevis. The mRNA for this gene can be first detected just after midblastula, peaks at late gastrula, and decays by the end of neurulation. The sequence of the DG42 cDNA and genomic DNA predicts a 70,000-Da protein that is not related to any other known protein. Antibodies prepared against portions of the DG42 open reading frame that had been expressed in bacteria detected a 70,000-Da protein in the embryo with a temporal course of appearance and decay that follows that of the RNA by several hours. Localization of the mRNA in dissected embryos and immunohistochemical detection of the protein showed that DG42 expression moves as a wave or gradient through the embryo. The RNA is first detected in the animal region of the blastula, and by early gastrula is found everywhere except in the outer layer of the dorsal blastopore lip. By midgastrula DG42 protein is present in the inner ectodermal layer and the endoderm; it disappears from dorsal ectoderm as the neural plate is induced and later decays in a dorsoventral direction. The last remnants of DG42 protein are seen in ventral regions of the gut at the tailbud stage.     

XK endo B is preferentially expressed in several induced embryonic tissues during the development of Xenopus laevis

XK endo B is a type I keratin that was originally identified by its preferential expression in the embryonic notochord of the amphibian Xenopus laevis. A peptide identical to a short region of its predicted amino acid sequence was used to generate antibodies against the XK endo B protein. This paper reports an immunocytochemical study of the spatial expression pattern of XK endo B during development. The protein was observed in the notochord and endoderm as predicted from previous RNA analysis. In addition, XK endo B was detected in the cement gland, in the pituitary, olfactory and pharyngeal pouch rudiments, and in a nonuniform distribution in the neural tube as well as the inner sensorial layer of the ectoderm. XK endo B expression is not limited to any germ layer or any particular cell type, but is nevertheless highly restricted in its distribution in the embryo. Its expression in several different embryonic tissues requiring inductive interactions for differentiation makes XK endo B a valuable tool with which to study the regulation of induced gene expression during embryogenesis.     

A developmentally regulated, nervous system-specific gene in Xenopus encodes a putative RNA-binding protein.

A gene from Xenopus laevis that is expressed specifically in the nervous system beginning at the stage of neural plate formation has been isolated and several cDNAs have been sequenced. The sequence of the predicted protein contains two copies of a presumed RNA-binding domain, each of which includes two short conserved motifs characteristic for ribonucleoproteins (RNPs), called the RNP-1 and RNP-2 consensus sequences. We name this gene Xenopus nrp-1, for nervous system-specific RNP protein-1. Sequence comparisons suggest that the nrp-1 protein is a heterogeneous nuclear RNP protein, but it is clearly distinct from previously reported hnRNP proteins such as the A1, A2/B1, and C1 proteins. nrp-1 RNA undergoes an alternative splicing event giving rise to two predicted protein isoforms that differ from each other by seven amino acids. In situ hybridization to tadpole brain shows that the nrp-1 gene is expressed in the ventricular zone where cell proliferation takes place. The occurrence of an RNP protein with nervous system-limited expression suggests that it may be involved in the tissue-specific control of RNA processing.     

Volatile-mediated signalling in barley induces metabolic reprogramming and resistance against the biotrophic fungus Blumeria hordei

• Plants have evolved diverse secondary metabolites to counteract biotic stress. Volatile organic compounds (VOCs) are released upon herbivore attack or pathogen infection. Recent studies suggest that VOCs can act as signalling molecules in plant defence and induce resistance in distant organs and neighbouring plants. However, knowledge is lacking on the function of VOCs in biotrophic fungal infection on cereal plants.
• We analysed VOCs emitted by 13 ± 1-day-old barley plants (Hordeum vulgare L.) after mechanical wounding using passive absorbers and TD-GC/MS. We investigated the effect of pure VOC and complex VOC mixtures released from wounded plants on the barley–powdery mildew interaction by pre-exposure in a dynamic headspace connected to a powdery mildew susceptibility assay. Untargeted metabolomics and lipidomics were applied to investigate metabolic changes in sender and receiver barley plants.
• Green leaf volatiles (GLVs) dominated the volatile profile of wounded barley plants, with (Z)-3-hexenyl acetate (Z3HAC) as the most abundant compound. Barley volatiles emitted after mechanical wounding enhanced resistance in receiver plants towards fungal infection. We found volatile-mediated modifications of the plant–pathogen interaction in a concentration-dependent manner. Pre-exposure with physiologically relevant concentrations of Z3HAC resulted in induced resistance, suggesting that this GLV is a key player in barley anti-pathogen defence.
• The complex VOC mixture released from wounded barley and Z3HAC induced e.g. accumulation of chlorophyll, linolenic acid and linolenate-conjugated lipids, as well as defence-related secondary metabolites, such as hordatines in receiving plants. Barley VOCs hence induce a complex physiological response and disease resistance in receiver plants.

     

The maternal-effect gene fsh is essential for the specification of the central region of the Drosophila embryo

The maternal-effect gene, female sterile (1) homeotic (fsh), has been implicated in the determination of segmental organization and identity. We have analyzed the spatial patterns of expression of several segmentation and homeotic genes in fsh-deficient embryos. We observed perturbations in the expression of the Ultrabithorax gene in parasegments 6, 7, and 8, consistent with the domain in which homeotic transformations occur in adults derived from such embryos. Further, the expression of the gap gene Krüppel and the pair-rule gene even-skipped is altered, especially in the central region of the embryo. Our results suggest that the defects in segmental organization in fsh-deficient progeny are mediated primarily but not exclusively through a restriction of the domain of Krüppel expression.