Maternal Embryo Effect Arrest 31 (MEE31) is a moonlighting protein involved in GDP-D-mannose biosynthesis and KAT1 potassium channel regulation

Due to anthropogenic global warming, droughts are expected to increase and water availability to decrease in the coming decades. For this reason, research is increasingly focused on developing plant varieties and crop cultivars with reduced water consumption. Transpiration occurs through stomatal pores, resulting in water loss. Potassium plays a significant role in stomatal regulation. KAT1 is an inward-rectifying potassium channel that contributes to stomatal opening. Using a yeast high-throughput screening of an Arabidopsis cDNA library, MEE31 was found to physically interact with KAT1. MEE31 was initially identified in a screen for mutants with delayed embryonic development. The gene encodes a conserved phosphomannose isomerase (PMI). We report here that MEE31 interacts with and increases KAT1 activity in yeast and this interaction was also confirmed in plants. In addition, MEE31 complements the function of the yeast homologue, whereas the truncated version recovered in the screening does not, thus uncoupling the enzymatic activity from KAT1 regulation. We show that MEE31 overexpression leads to increased stomatal opening in Arabidopsis transgenic lines. Our data suggest that MEE31 is a moonlighting protein involved in both GDP-D-mannose biosynthesis and KAT1 regulation.

Novel findings about the mode of action of the antifungal protein PeAfpA against Saccharomyces cerevisiae

Antifungal proteins (AFPs) from filamentous fungi offer the potential to control fungal infections that threaten human health and food safety. AFPs exhibit broad antifungal spectra against harmful fungi, but limited knowledge of their killing mechanism hinders their potential applicability. PeAfpA from Penicillium expansum shows strong antifungal potency against plant and human fungal pathogens and stands above other AFPs for being active against the yeast Saccharomyces cerevisiae. We took advantage of this and used a model laboratory strain of S. cerevisiae to gain insight into the mode of action of PeAfpA by combining (i) transcriptional profiling, (ii) PeAfpA sensitivity analyses of deletion mutants available in the S. cerevisiae genomic deletion collection and (iii) cell biology studies using confocal microscopy. Results highlighted and confirmed the role of the yeast cell wall (CW) in the interaction with PeAfpA, which can be internalized through both energy-dependent and independent mechanisms. The combined results also suggest an active role of the CW integrity (CWI) pathway and the cAMP-PKA signalling in the PeAfpA killing mechanism. Besides, our studies revealed the involvement of phosphatidylinositol metabolism and the participation of ROX3, which codes for the subunit 19 of the RNA polymerase II mediator complex, in the yeast defence strategy. In conclusion, our study provides clues about both the killing mechanism of PeAfpA and the fungus defence strategies against the protein, suggesting also targets for the development of new antifungals. KEY POINTS: • PeAfpA is a cell-penetrating protein with inhibitory activity against S. cerevisiae. • The CW integrity (CWI) pathway is a key player in the PeAfpA killing mechanism. • Phosphatidylinositol metabolism and ROX3 are involved in the yeast defence strategy.

Transcriptomic Profile of Penicillium digitatum Reveals Novel Aspects of the Mode of Action of the Antifungal Protein AfpB

Antifungal proteins (AFPs) from filamentous fungi are promising biomolecules to control fungal pathogens. Understanding their biological role and mode of action is essential for their future application. AfpB from the citrus fruit pathogen Penicillium digitatum is highly active against fungal phytopathogens, including its native fungus. Our previous data showed that AfpB acts through a multitargeted three-stage process: interaction with the outer mannosylated cell wall, energy-dependent cell internalization, and intracellular actions that result in cell death. Here, we extend these findings by characterizing the functional role of AfpB and its interaction with P. digitatum through transcriptomic studies. For this, we compared the transcriptomic response of AfpB-treated P. digitatum wild type, a ΔafpB mutant, and an AfpB-overproducing strain. Transcriptomic data suggest a multifaceted role for AfpB. Data from the ΔafpB mutant suggested that the afpB gene contributes to the overall homeostasis of the cell. Additionally, these data showed that AfpB represses toxin-encoding genes, and they suggest a link to apoptotic processes. Gene expression and knockout mutants confirmed that genes coding for acetolactate synthase (ALS) and acetolactate decarboxylase (ALD), which belong to the acetoin biosynthetic pathway, contribute to the inhibitory activity of AfpB. Moreover, a gene encoding a previously uncharacterized extracellular tandem repeat peptide (TRP) protein showed high induction in the presence of AfpB, whereas its TRP monomer enhanced AfpB activity. Overall, our study offers a rich source of information to further advance in the characterization of the multifaceted mode of action of AFPs. IMPORTANCE Fungal infections threaten human health worldwide and have a negative impact on food security, damaging crop production and causing animal diseases. At present, only a few classes of fungicides are available due to the complexity of targeting fungi without affecting plant, animal, or human hosts. Moreover, the intensive use of fungicides in agriculture has led to the development of resistance. Therefore, there is an urgent need to develop antifungal biomolecules with new modes of action to fight human-, animal-, and plant-pathogenic fungi. Fungal antifungal proteins (AFPs) offer great potential as new biofungicides to control deleterious fungi. However, current knowledge about their killing mechanism is still limited, which hampers their potential applicability. AfpB from P. digitatum is a promising molecule with potent and specific fungicidal activity. This study further characterizes its mode of action, opening avenues for the development of new antifungals.

Development of a FungalBraid Penicillium expansum-based expression system for the production of antifungal proteins in fungal biofactories

Fungal antifungal proteins (AFPs) have attracted attention as novel biofungicides. Their exploitation requires safe and cost‐effective producing biofactories. Previously, Penicillium chrysogenum and Penicillium digitatum produced recombinant AFPs with the use of a P. chrysogenum‐based expression system that consisted of the paf gene promoter, signal peptide (SP)‐pro sequence and terminator. Here, the regulatory elements of the afpA gene encoding the highly produced PeAfpA from Penicillium expansum were developed as an expression system for AFP production through the FungalBraid platform. The afpA cassette was tested to produce PeAfpA and P. digitatum PdAfpB in P. chrysogenum and P. digitatum, and its efficiency was compared to that of the paf cassette. Recombinant PeAfpA production was only achieved using the afpA cassette, being P. chrysogenum a more efficient biofactory than P. digitatum. Conversely, P. chrysogenum only produced PdAfpB under the control of the paf cassette. In P. digitatum, both expression systems allowed PdAfpB production, with the paf cassette resulting in higher protein yields. Interestingly, these results did not correlate with the performance of both promoters in a luciferase reporter system. In conclusion, AFP production is a complex outcome that depends on the regulatory sequences driving afp expression, the fungal biofactory and the AFP sequence.

BCL2-ASSOCIATED ATHANOGENE4 Regulates the KAT1 Potassium Channel and Controls Stomatal Movement

Potassium (K+) is a key monovalent cation necessary for multiple aspects of cell growth and survival. In plants, this cation also plays a key role in the control of stomatal movement. KAT1 and its homolog KAT2 are the main inward rectifying channels present in guard cells, mediating K+ influx into these cells, resulting in stomatal opening. To gain further insight into the regulation of these channels, we performed a split-ubiquitin protein-protein interaction screen searching for KAT1 interactors in Arabidopsis (Arabidopsis thaliana). We characterized one of these candidates, BCL2-ASSOCIATED ATHANOGENE4 (BAG4), in detail using biochemical and genetic approaches to confirm this interaction and its effect on KAT1 activity. We show that BAG4 improves KAT1-mediated K+ transport in two heterologous systems and provide evidence that in plants, BAG4 interacts with KAT1 and favors the arrival of KAT1 at the plasma membrane. Importantly, lines lacking or overexpressing the BAG4 gene show altered KAT1 plasma membrane accumulation and alterations in stomatal movement. Our data allowed us to identify a KAT1 regulator and define a potential target for the plant BAG family. The identification of physiologically relevant regulators of K+ channels will aid in the design of approaches that may impact drought tolerance and pathogen susceptibility.

Saccharomyces cerevisiae as a Tool to Investigate Plant Potassium and Sodium Transporters

Sodium and potassium are two alkali cations abundant in the biosphere. Potassium is essential for plants and its concentration must be maintained at approximately 150 mM in the plant cell cytoplasm including under circumstances where its concentration is much lower in soil. On the other hand, sodium must be extruded from the plant or accumulated either in the vacuole or in specific plant structures. Maintaining a high intracellular K+/Na+ ratio under adverse environmental conditions or in the presence of salt is essential to maintain cellular homeostasis and to avoid toxicity. The baker's yeast, Saccharomyces cerevisiae, has been used to identify and characterize participants in potassium and sodium homeostasis in plants for many years. Its utility resides in the fact that the electric gradient across the membrane and the vacuoles is similar to plants. Most plant proteins can be expressed in yeast and are functional in this unicellular model system, which allows for productive structure-function studies for ion transporting proteins. Moreover, yeast can also be used as a high-throughput platform for the identification of genes that confer stress tolerance and for the study of protein-protein interactions. In this review, we summarize advances regarding potassium and sodium transport that have been discovered using the yeast model system, the state-of-the-art of the available techniques and the future directions and opportunities in this field.

Genome Wide Binding Site Analysis Reveals Transcriptional Coactivation of Cytokinin-Responsive Genes by DELLA Proteins

The ability of plants to provide a plastic response to environmental cues relies on the connectivity between signaling pathways. DELLA proteins act as hubs that relay environmental information to the multiple transcriptional circuits that control growth and development through physical interaction with transcription factors from different families. We have analyzed the presence of one DELLA protein at the Arabidopsis genome by chromatin immunoprecipitation coupled to large-scale sequencing and we find that it binds at the promoters of multiple genes. Enrichment analysis shows a strong preference for cis elements recognized by specific transcription factor families. In particular, we demonstrate that DELLA proteins are recruited by type-B ARABIDOPSIS RESPONSE REGULATORS (ARR) to the promoters of cytokinin-regulated genes, where they act as transcriptional co-activators. The biological relevance of this mechanism is underpinned by the necessity of simultaneous presence of DELLAs and ARRs to restrict root meristem growth and to promote photomorphogenesis.

Plants respond to environmental cues by modulating transcriptional circuits. One mechanism for such modulation involves DELLA proteins. They are promiscuous interactors of transcription factors and, in most cases, this interaction impairs the recognition of the DNA target sequences. Here we show that DELLA proteins are also recruited to multiple locations of the genome where they act as transcriptional coactivators, and we demonstrate how physical interaction with type-B ARRs is relevant for the regulation of meristem maintenance and photomorphogenesis.

The transcriptional regulator BBX24 impairs DELLA activity to promote shade avoidance in Arabidopsis thaliana

In response to canopy shade, plant vegetative structures elongate to gain access to light. However, the mechanism that allows a plastic transcriptional response to canopy shade light is not fully elucidated. Here we propose that the activity of PIF4, a key transcription factor in the shade signalling network, is modulated by the interplay between the BBX24 transcriptional regulator and DELLA proteins, which are negative regulators of the gibberellin (GA) signalling pathway. We show that GA-related targets are enriched among genes responsive to BBX24 under shade and that the shade-response defect in bbx24 mutants is rescued by a GA treatment that promotes DELLA degradation. BBX24 physically interacts with DELLA proteins and alleviates DELLA-mediated repression of PIF4 activity. The proposed molecular mechanism provides reversible regulation of the activity of a key transcription factor that may prove especially relevant under fluctuating light conditions.

The ascidian pigmented sensory organs: structures and developmental programs

The recent advances on ascidian pigment sensory organ development and function represent a fascinating platform to get insight on the basic programs of chordate eye formation. This review aims to summarize current knowledge, at the structural and molecular levels, on the two main building blocks of ascidian light sensory organ, i.e. pigment cells and photoreceptor cells. The unique features of these structures (e.g., simplicity and well characterized cell lineage) are indeed making it possible to dissect the developmental programs at single cell resolution and will soon provide a panel of molecular tools to be exploited for a deep developmental and comparative-evolutionary analysis.

Current perspectives on the hormonal control of seed development in Arabidopsis and maize: a focus on auxin

The seed represents the unit of reproduction of flowering plants, capable of developing into another plant, and to ensure the survival of the species under unfavorable environmental conditions. It is composed of three compartments: seed coat, endosperm and embryo. Proper seed development depends on the coordination of the processes that lead to seed compartments differentiation, development and maturation. The coordination of these processes is based on the constant transmission/perception of signals by the three compartments. Phytohormones constitute one of these signals; gradients of hormones are generated in the different seed compartments, and their ratios comprise the signals that induce/inhibit particular processes in seed development. Among the hormones, auxin seems to exert a central role, as it is the only one in maintaining high levels of accumulation from fertilization to seed maturation. The gradient of auxin generated by its PIN carriers affects several processes of seed development, including pattern formation, cell division and expansion. Despite the high degree of conservation in the regulatory mechanisms that lead to seed development within the Spermatophytes, remarkable differences exist during seed maturation between Monocots and Eudicots species. For instance, in Monocots the endosperm persists until maturation, and constitutes an important compartment for nutrients storage, while in Eudicots it is reduced to a single cell layer, as the expanding embryo gradually replaces it during the maturation. This review provides an overview of the current knowledge on hormonal control of seed development, by considering the data available in two model plants: Arabidopsis thaliana, for Eudicots and Zea mays L., for Monocots. We will emphasize the control exerted by auxin on the correct progress of seed development comparing, when possible, the two species.

Genomic analysis of DELLA protein activity

Changes in gene expression are the main outcome of hormone signaling cascades that widely control plant physiology. In the case of the hormones gibberellins, the transcriptional control is exerted through the activity of the DELLA proteins, which act as negative regulators in the signaling pathway. This review focuses on recent transcriptomic approaches in the context of gibberellin signaling, which have provided useful information on new processes regulated by these hormones such as the regulation of photosynthesis and gravitropism. Moreover, the enrichment of specific cis-elements among DELLA primary targets has also helped extend the view that DELLA proteins regulate gene expression through the interaction with multiple transcription factors from different families.

Dynamic regulation of cortical microtubule organization through prefoldin-DELLA interaction

Plant morphogenesis relies on specific patterns of cell division and expansion. It is well established that cortical microtubules influence the direction of cell expansion, but less is known about the molecular mechanisms that regulate microtubule arrangement. Here we show that the phytohormones gibberellins (GAs) regulate microtubule orientation through physical interaction between the nuclear-localized DELLA proteins and the prefoldin complex, a cochaperone required for tubulin folding. In the presence of GA, DELLA proteins are degraded, and the prefoldin complex stays in the cytoplasm and is functional. In the absence of GA, the prefoldin complex is localized to the nucleus, which severely compromises α/β-tubulin heterodimer availability, affecting microtubule organization. The physiological relevance of this molecular mechanism was confirmed by the observation that the daily rhythm of plant growth was accompanied by coordinated oscillation of DELLA accumulation, prefoldin subcellular localization, and cortical microtubule reorientation.

Characterisation of ALS genes in the polyploid species Schoenoplectus mucronatus and implications for resistance management

BACKGROUND

The polyploid weed Schoenoplectus mucronatus (L.) Palla has evolved target-site resistance to ALS-inhibiting herbicides in Italian rice crops. Molecular and genetic characterisation of the resistance mechanism is relevant to the evolution and management of herbicide resistance. The authors aimed (a) to study the organisation of the target-site loci in two field-selected S. mucronatus populations with different cross-resistance patterns, (b) to identify the mutations endowing resistance to ALS inhibitors and determine the role of these mutations by using transgenesis and (c) to analyse the implications for the management of the S. mucronatus populations.

RESULTS

Two complete ALS genes (ALS1 and ALS2) having an intron and a third partial intronless ALS gene (ALS3) were identified. The presence of multiple ALS genes was confirmed by Southern blot analyses, and ALS loci were characterised by examining cytosine methylation. In S. mucronatus leaves, the transcripts of ALS1, ALS2 and ALS3 were detected. Two mutations endowing resistance (Pro(197) to His and Trp(574) to Leu) were found in both resistant populations, but at different frequencies. Tobacco plants transformed with the two resistant alleles indicated that the Pro(197)-to-His substitution conferred resistance to SU and TP herbicides, while the allele with the Trp(574)-to-Leu substitution conferred cross-resistance to SU, TP, IMI and PTB herbicides.

CONCLUSION

Schoenoplectus mucronatus has multiple ALS genes characterised by methylated sites that can influence the expression profile. The two mutated alleles proved to be responsible for ALS resistance. At population level, the resistance pattern depends on the frequency of various resistant genotypes, and this influences the efficacy of various ALS-inhibiting herbicides.

Characterization of a MADS FLOWERING LOCUS C-LIKE (MFL) sequence in Cichorium intybus: a comparative study of CiMFL and AtFLC reveals homologies and divergences in gene function

In Arabidopsis thaliana, the ability to flower is mainly related to a floral repressor, FLOWERING LOCUS C (FLC), which is regulated through the vernalization pathway. The genes controlling the vernalization pathway seem to be only partially conserved in dicots other than the Brassicaceae. Cichorium intybus (chicory) is a biennial species belonging to the Asteraceae family, and it shows an obligate vernalization requirement for flowering. Cichorium intybus MADS (MCM1, Agamous, Deficiens, SRF) FLC-like (CiMFL) sequences were isolated in C. intybus by RT-PCR and their expression patterns characterized during plant development and in response to vernalization. The biological function of CiMFL was analysed by complementation of A. thaliana FRIGIDA (AtFRI);flc3. Resetting of MFL expression after vernalization was analysed during microsporogenesis. Before vernalization, CiMFL is mainly expressed in the axils of young leaves. Vernalization induced CiMFL down-regulation under a long-day photoperiod but not under a short-day photoperiod. Furthermore, together with a decrease in CiMFL transcripts, cold conditions induced changes in the morphology of the shoot apical meristem and in the transition to flowering. The biological function of CiMFL was found not to be conserved. Our results show that the regulation of CiMFL expression in time and space and in relation to environmental conditions is only partially conserved with respect to FLC isolated from A. thaliana. A model for flowering repression by CiMFL is proposed.

PLAUF binding to the 3′UTR of the H3.3 histone transcript affects mRNA stability

In P. lividus sea urchin the H3.3 histone variant is coded by an mRNA characterized by a long 3'UTR containing ARE (AU-Rich element) motifs. RNA stability assays performed in rabbit reticulocyte lysate showed that such 3'UTR affects the degradation rate of the transcripts. In fact, chimeric molecules containing the 3'UTR of H3.3 transcript, ligated to the coding region of the rabbit beta-globin transcript, were unstable whereas chimeric molecules containing mainly the coding region of the H3.3 transcript were stable as the wild-type globin mRNA. Three proteins (45kDa, 32kDa and 25kDa) that bind specifically the 3'UTR have been revealed in the whole protein extracts of embryos at different stages of development. PLAUF, a P. lividus RNA-binding protein similar to human and rodent AUF1 proteins, was identified as the 32kDa factor using anti-PLAUF antibody in Western blot and supershift mobility assays. Moreover the recombinant GST-PLAUF protein specifically binds part of the H3.3 3'UTR and in vitro affects the half-life of the transcript. In addition in situ hybridization experiments demonstrated that PLAUF and H3.3 histone mRNAs co-localize in embryos at different stages of development. In conclusion all the reported results suggest that PLAUF can bind in vivo the 3'UTR of the H3.3 histone mRNA and plays some role in the stability of the mRNA.

Cell movements during vertebrate development: integrated tissue behaviour versus individual cell migration

Cell migration during development is fundamental to the establishment of the embryonic architecture. Depending on the context, cells may move either as integrated sheets of tissue or individually. Recently, molecules that are involved in both these types of cell behaviour have been identified, helping us to understand developmental processes as important as gastrulation and neural crest formation, and ultimately, the morphogenetic movements that shape the embryo.

A new role for E12/E47 in the repression of E-cadherin expression and epithelial-mesenchymal transitions

Down-regulation of E-cadherin expression is a determinant of tumor cell invasiveness, an event frequently associated with epithelial-mesenchymal transitions. Here we show that the mouse E12/E47 basic helix-loop-helix transcription factor (the E2A gene product) acts as a repressor of E-cadherin expression and triggers epithelial-mesenchymal transitions. The mouse E47 factor was isolated in a one-hybrid system designed to isolate repressors of the mouse E-cadherin promoter. Epithelial cells ectopically expressing E47 adopt a fibroblastic phenotype and acquire tumorigenic and migratory/invasive properties, concomitant with the suppression of E-cadherin expression. Suppression of E-cadherin expression under stable or inducible expression of E47 in epithelial cells occurs at the transcriptional level and is dependent on the E-boxes of the E-cadherin promoter. Interestingly, analysis of endogenous E2A expression in murine and human cell lines illustrated its presence in E-cadherin-deficient, invasive carcinoma cells but its absence from epithelial cell lines. This expression pattern is consistent with that observed in early mouse embryos, where E2A mRNA is absent from epithelia but strongly expressed in the mesoderm. These results implicate E12/E47 as a repressor of E-cadherin expression during both development and tumor progression and indicate its involvement in the acquisition and/or maintenance of the mesenchymal phenotype.

DNA (cytosine-5) methyltransferase turnover and cellular localization in developing Paracentrotus lividus sea urchin embryo

The turnover and localization of the enzyme DNA (cytosine-5) methyltransferase (Dnmt1) were studied during Paracentrotus lividus sea urchin embryo development using antibody preparations against the NH(2) and COOH-terminal regions of the molecule. The antibodies reveal, by Western blots and whole-mount analyses, that the enzyme is differently required during embryonic development. The changeover point is at blastula stage, where a proteolytic mechanism hydrolyses the enzyme present in all embryonic cells by removing a peptide of about 45 kDa from the amino terminal region of the 190 kDa enzyme initially synthesized on maternal transcripts. The resulting 145 kDa enzyme shows modified catalytic properties, different antibody reactivity and is rapidly destroyed in the few hours before gastrulation. At more advanced stages of development the enzyme is newly synthesized but only in particular cell types, among which neurons. The data show that Dnmt1 is removed from embryonic cells before gastrulation to be synthesized again at different levels in different cell types, indicating that the concentration of Dnmt1 is critical for the various differentiated cells of the developing sea urchin embryo.

The increasing complexity of the Snail gene superfamily in metazoan evolution

The Snail family of zinc-finger transcription factors is involved not only in the development of vertebrate and invertebrate embryos, but also in tumour progression. Following the identification of eight new members, we have analysed the evolutionary history of these genes and found that they constitute a superfamily that groups two independent families, Snail and Scratch. We propose that the duplication of an ancestral gene at the time of the metazoan radiation (1000-500 Myr ago) gave rise to Snail and Scratch, and that independent duplications in protostomes and deuterostomes led to the present situation. We discuss the implications of the distinct duplication events on the acquisition of new functions.

The transcription factor snail controls epithelial-mesenchymal transitions by repressing E-cadherin expression

The Snail family of transcription factors has previously been implicated in the differentiation of epithelial cells into mesenchymal cells (epithelial-mesenchymal transitions) during embryonic development. Epithelial-mesenchymal transitions are also determinants of the progression of carcinomas, occurring concomitantly with the cellular acquisition of migratory properties following downregulation of expression of the adhesion protein E-cadherin. Here we show that mouse Snail is a strong repressor of transcription of the E-cadherin gene. Epithelial cells that ectopically express Snail adopt a fibroblastoid phenotype and acquire tumorigenic and invasive properties. Endogenous Snail protein is present in invasive mouse and human carcinoma cell lines and tumours in which E-cadherin expression has been lost. Therefore, the same molecules are used to trigger epithelial-mesenchymal transitions during embryonic development and in tumour progression. Snail may thus be considered as a marker for malignancy, opening up new avenues for the design of specific anti-invasive drugs.

Patterning the ascidian nervous system: structure, expression and transgenic analysis of the CiHox3 gene

Hox genes play a fundamental role in the establishment of chordate body plan, especially in the anteroposterior patterning of the nervous system. Particularly interesting are the anterior groups of Hox genes (Hox1-Hox4) since their expression is coupled to the control of regional identity in the anterior regions of the nervous system, where the highest structural diversity is observed. Ascidians, among chordates, are considered a good model to investigate evolution of Hox gene, organisation, regulation and function. We report here the cloning and the expression pattern of CiHox3, a Ciona intestinalis anterior Hox gene homologous to the paralogy group 3 genes. In situ hybridization at the larva stage revealed that CiHox3 expression was restricted to the visceral ganglion of the central nervous system. The presence of a sharp posterior boundary and the absence of transcript in mesodermal tissues are distinctive features of CiHox3 expression when compared to the paralogy group 3 in other chordates. We have investigated the regulatory elements underlying CiHox3 neural-specific expression and, using transgenic analysis, we were able to isolate an 80 bp enhancer responsible of CiHox3 activation in the central nervous system (CNS). A comparative study between mouse and Ciona Hox3 promoters demonstrated that divergent mechanisms are involved in the regulation of these genes in vertebrates and ascidians.

Identification and developmental expression of Ci-msxb: a novel homologue of Drosophila msh gene in Ciona intestinalis

We report the cloning and expression pattern of Ci-msxb the second Ciona intestinalis homeobox gene homologue to the Drosophila muscle segment homeobox (msh) gene. Northern blot analysis showed that transcripts appeared at gastrula stage, peaked in the early tailbud and decreased during the tailed stages. Whole mount in situ hybridization showed that the Ci-msxb expression first is detected at 110 cell-stage in the blastomeres that are precursors of different tissue (muscle, spinal cord, endodermal strand, brain, mesenchyme, pigmented cells and primordial pharynx). Transcript level declined in mesoderm cells after the completion of gastrulation, but mRNAs were still present in the folding neural plate during neurulation and in the pigmented cells. Later, at larval stage, transcripts were present around the otolith and ocellus, in a restricted part of the nervous system and in the primordial pharynx; the gene expression was conserved after metamorphosis in the juvenile.

Developmental regulation and tissue-specific localization of calmodulin mRNA in the protochordate Ciona intestinalis

A full-length cDNA encoding a highly conserved calmodulin was isolated from a cDNA library prepared from hatched larvae of the ascidian Ciona intestinalis. Sequence analysis has identified a 447 b.p. open reading frame, encoding a putative protein of 149 amino acid residues, with a predicted molecular weight of 16.8 kDa, showing 85-98% identity to known calmodulins. Northern blot analysis revealed a single transcript of about 0.8 kb in length, which was maternally expressed and progressively increased during development, until late tail-bud stage. Whole-mount in situ hybridizations, carried out on embryos at different stages of development, showed that starting from the neurula stage, the C. intestinalis calmodulin (Ci-CaM) expression became restricted to the neuroectoderm and that in larvae it was specifically detected in the nervous system.

Isolation of cDNA clones encoding DNA methyltransferase of sea urchin P. lividus: expression during embryonic development

A full-length cDNA, encoding a DNA (cytosine-5)-methyltransferase (DNA MTase), has been assembled from a series of overlapping cDNA clones isolated from P. lividus sea urchin embryo cDNA libraries. The cDNA contains 103 bp 5'-UTR, 4839 bp open reading frame corresponding to a 1612 amino acids (aa) protein and 2240 bp 3'-UTR including a terminal 18-bp poly(A) tail. Both the cDNA and the encoded protein are the longest so far reported for DNA MTases. The protein shows five distinct and sequential regions of identity with the other animal DNA MTases, with values of identity from zero to 80%. Northern blot analyses reveal a single RNA band of about 7.5 kb in length showing a highly regulated concentration pattern during development with peak value at the four blastomere stage.