No abstract

Key message The composition of homogalacturonans (HGs) in the ovule and the female gametophyte cell walls was shown to be rearranged dynamically during sexual reproduction of H. orientalis. Abstract In angiosperms, homogalacturonans (HGs) play an important role in the interaction between the male gametophyte and the pistil transmitting tract, but little is known about the participation of these molecules at the final stage of the progamic phase and fertilization. The aim of our study was to perform immunocytochemical localization of highly (JIM7 MAb) and weakly (JIM5 MAb) methyl esterified and Ca 2? -associated HG (2F4 MAb) in the ovule and female gametophyte cells of Hyacinthus orientalis before and after fertilization. It was found that pollination induced the rearrangement of HG in (1) the micropylar canal of the ovule, (2) the filiform apparatus of the synergids, and (3) the region of fusion between sperm cells and their target cells. Fertilization led to further changes in pectin composition of these three regions of the ovule. A new cell wall was synthesized around the zygote with a characteristic pattern of localization of all examined HG fractions, which we called ''sporoderm-like''. The developing endosperm prepared for cellularization by synthesizing highly methyl-esterified HG, which was stored in the cytoplasm. Pollination-and fertilizationinduced changes in the composition of the HG in the micropyle of the ovule and the apoplast of female gametophyte cells are discussed in the context of: (1) micropylar pollen tube guidance, (2) preparation of the egg cell and the central cells for fusion with sperm cells, and (3) the polyspermy block.

Highlight:Under physiological conditions, it was shown that the same cell model may establish two distinct spatial manners of cytoplasmic snRNP assembly.

Transcriptional hypoxia-inducible factor-1α (HIF-1α) plays the fundamental role in adaptive processes in response to hypoxia. Specific HIF-1α target genes are involved in glycolysis, erythropoiesis and angiogenesis to promote survival. In our previous study we have demonstrated that naturally low body temperature of newborn rats protects them against damage due to perinatal hypoxia. Therefore, our experiments aimed at checking the effects of body temperature during simulated perinatal anoxia on subsequent changes of expression of HIF-1α and its specific target genes such as vascular endothelial growth factor (VEGF) and erythropoietin (EPO) in the rat brain. Two-day old Wistar rats were divided into three temperature groups: normothermic -33 °C, hyperthermic -37 °C and extremely hyperthermic -39 °C. The temperature was controlled 15 min before start and continued during 10 min of anoxia as well as for 2 h post-anoxia. HIF-1α was analysed by Western blot and immunofluorescence and mRNA levels of HIF-1α and its downstream genes (VEGF, EPO) were quantified by qRT-PCR. Thermal conditions during neonatal anoxia affected the hippocampal and neocortical level of HIF-1α protein. Physiological body temperature of newborn rats led to prominent accumulation of cerebral HIF-1α protein and significant upregulation of VEGF and EPO mRNA. In contrast, anoxia-induced HIF-1α activation at elevated body temperatures was less pronounced. Since HIF-1α and EPO have recently been regarded as promising therapeutical targets against brain lesions due to hypoxia/ischemia, presented data imply that in order to achieve a full effect of neuroprotection, the thermal conditions during and after the insult should be taken into consideration.

ABSTRACTIn light of recent studies, many of the cytoplasmic posttranscriptional mRNA processing steps take place in highly specialized microdomains referred to as cytoplasmic bodies. These evolutionarily conserved microdomains are sites of regulation for both mRNA translation and degradation. It has been shown that in the larch microsporocyte cytoplasm, there is a significant pool of Sm proteins not related to snRNP complexes. These Sm proteins accumulate within distinct cytoplasmic bodies (S-bodies) that also contain mRNA. Sm proteins constitute an evolutionarily ancient family of small RNA-binding proteins. In eukaryotic cells, these molecules are involved in pre-mRNA splicing. The latest research indicates that in addition to this well-known function, Sm proteins could also have an impact on mRNA at subsequent stages of its life cycle. The aim of this work was to verify the hypothesis that canonical Sm proteins are part of the cytoplasmic mRNP complex and thus function in the posttranscriptional regulation of gene expression in plants.