The regulation of dendritic branching is critical for sensory reception, cell−cell communication within the nervous system, learning, memory, and behavior. Defects in dendrite morphology are associated with several neurologic disorders; thus, an understanding of the molecular mechanisms that govern dendrite morphogenesis is important. Recent investigations of dendrite morphogenesis have highlighted the importance of gene regulation at the posttranscriptional level. Because RNA-binding proteins mediate many posttranscriptional mechanisms, we decided to investigate the extent to which conserved RNA-binding proteins contribute to dendrite morphogenesis across phyla. Here we identify a core set of RNA-binding proteins that are important for dendrite morphogenesis in the PVD multidendritic sensory neuron in Caenorhabditis elegans. Homologs of each of these genes were previously identified as important in the Drosophila melanogaster dendritic arborization sensory neurons. Our results suggest that RNA processing, mRNA localization, mRNA stability, and translational control are all important mechanisms that contribute to dendrite morphogenesis, and we present a conserved set of RNA-binding proteins that regulate these processes in diverse animal species. Furthermore, homologs of these genes are expressed in the human brain, suggesting that these RNA-binding proteins are candidate regulators of dendrite development in humans.
The main postharvest disorder of cut gerbera flowers is the stem bending and break. The cause of stem bending is not completely clear. Although the genetic background seems to play the major role, some plant hormones such as ethylene and cytokinins may enhance or reduce the incidence of stem break during postharvest life. The choice of withstand genotypes seems to be a good strategy. In fact, stem bending incidence strongly varies among cultivars. The aim of this work was to evaluate the role of PAL activity and tissue lignifications on stem bending. Cut gerbera flowers were obtained from local growers and immediately transferred to postharvest evaluation room. Cut flowers were screened and selected in order to have homogenous samples. Chemicals were applied as pulse treatments for 24 h using 2 mM amino-oxyacetic acid (AOA), 1 mM α-aminooxi-β-phenylpropionic acid (AOPP) or 100 µl L-1 ethylene. During postharvest life the stem elongation, stem bending, PAL activity and vase life were measured. Results showed a strong variation of stem bending incidence among cultivars. Pulse treatments with PAL inhibitors such as AOA and AOPP strongly increased stem bending even after 1-2 days after treatments. Ethylene reduced the stem bending incidence increasing the PAL activity.
The Caenorhabditis elegans gene sup-26 encodes a well-conserved RNA-recognition motif-containing RNA-binding protein (RBP) that functions in dendrite morphogenesis of the PVD sensory neuron. The Drosophila ortholog of sup-26, alan shepard (shep), is expressed throughout the nervous system and has been shown to regulate neuronal remodeling during metamorphosis. Here, we extend these studies to show that sup-26 and shep are required for the development of diverse cell types within the nematode and fly nervous systems during embryonic and larval stages. We ascribe roles for sup-26 in regulating dendrite number and the expression of genes involved in mechanosensation within the nematode peripheral nervous system. We also find that in Drosophila, shep regulates dendrite length and branch order of nociceptive neurons, regulates the organization of neuronal clusters of the peripheral nervous system and the organization of axons within the ventral nerve cord. Taken together, our results suggest that shep/sup-26 orthologs play diverse roles in neural development across animal species. Moreover, we discuss potential roles for shep/sup-26 orthologs in the human nervous system.
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