Calmodulin Localization and its Effects on Endocytic and Phagocytic Membrane Trafficking in Paramecium multimicronucleatum

ABSTRACT. In ciliates, calmodulin (CaM), as in other cells, has multiple functions, such as activation of regulatory enzymes and modulating calcium‐dependent cellular processes. By immunogold localization, CaM is concentrated at multiple sites in Paramecium. It is seen scattered over the cytosol, but bound to its matrix, and is concentrated at the pores of the contractile vacuole complexes and with at least three microtubular arrays. It was localized peripheral to the nine‐doublet microtubules of the ciliary axonemes. The most striking localization was on the akinetic side only of the cytopharyngeal microtubular ribbons opposite the side where the discoidal vesicles, acidosomes and the 100‐nm carrier vesicles bind and move. CaM was also present at the periphery of the postoral microtubular bundles along which the early vacuole moves and was associated with the cytoproct microtubules that guide the spent digestive vacuoles to the cytoproct. It was not found on the membranes of, or in the interior of nuclei, mitochondria, phagosomes, and trichocysts, and was only sparsely scattered over the cytosolic sides of discoidal vesicles, acidosomes, lysosomes, and digestive vacuoles. Together the associations with specific microtubular arrays and the effects of trifluoperazine and calmidazolium indicate that CaM is involved (i) in vesicle transport to the cytopharynx area for vacuole formation and subsequent vacuole acidification, (ii) in early vacuole transport along the postoral fiber, and (iii) in transporting the spent vacuole to the cytoproct. Higher CaM concentrations subjacent to the cell's pellicle and close to the decorated tubules of the contractile vacuole complex may support a role for CaM in ion traffic.     

Photomorphogenesis in Pteris vittata II. Recovery from blue-light-induced inhibition of spore germination

1. 1. In the fern Pteris vittata, low-energy blue-light-inducedinhibition of phytochrome-dependent spore germination and darkrecovery from this inhibition were repeatedly observed severaltimes at intervals of 3 days at 26. The same amount of incidentenergy of blue light was required for inhibition in each successivetreatment.
2. 2. The recovery from blue-light-induced inhibitionof germinationwas markedly accelerated by continuous illuminationwith redlight, and this red light effect was not affected bythe presenceof CMU.
3. 3. The recovery process was not influencedby a single exposureto redlight, but was definitely promotedby brief red irradiationsgiven intermittently, at least 2 times,at equal intervals duringthe first 8 hr after blue light treatment.The effect of intermittentlygiven red light was annulled wheneach red exposure was followedby brief far-red irradiation.These facts suggest that phytochromemay be involved in therestoration of the ability of sporesto germinate (in responseto red light) which had been lostby blue irradiation.

¹Present address: Botany Department, Faculty of Science, Universityof Tokyo, Hongo, Tokyo 113.     

PHYTOCHROME ACTION IN ORYZA SATIVA L.: I. GROWTH RESPONSES OF ETIOLATED COLEOPTILES TO RED, FAR-RED AND BLUE LIGHT

1. Under continuous irradiation, the growth of intact rice coleoptilewas strongly inhibited by red light, and somewhat preventedby blue and far-red light. The inhibitory effect of red lighton coleoptile elongation was caused by a low-energy brief irradiation,and a single exposure of 1.5 kiloergs cm^–2 incidentenergy of red light brought about the 50% inhibition. This photoinhibitionof growth was observed only after the coleoptile had elongatedto about 10 mm or longer. The red light-induced effect was reversedby an immediately following brief exposure to far-red light,and the photoresponses to red and far-red light were repeatedlyreversible. The escape reaction of red lightinduced effect tookplace at a rate so that 50% of the initial reversibility waslost within 9 hr in darkness at 27. The inhibition by bluelight and reversal by far-red irradiation was also achievedrepeatedly with successive treatments of the coleoptiles. Theevidence for a low intensity red far-red reversible controlof coleoptile growth, indicative of control by phytochrome,seems clearly established in etiolated intact seedlings.
2. Incontrast, the elongation of apically excised rice coleoptilesegments was promoted by a brief exposure to red light in 0.02M phosphate buffer, pH 7, and the effect was almost completelynullified by an immediately subsequent exposure to far-red light.It becomes evident that the growth of intact coleoptiles wasinhibited by a exposure to red light, while that of excisedsegments in a buffer was rather promoted by red irradiation.The direction of red light induced responses, either promotiveor inhibitory, depends upon the method of bioassay using intactcoleoptiles or their excised segments.

(Received July 24, 1967; )     

EFFECTS OF ENVIRONMENTAL FACTORS ON MECHANICAL PROPERTIES OF THE CELL WALL IN RICE COLEOPTILES

Cell wall properties determined by the stress-relaxation technique were studied with coleoptiles of rice seedlings grown under different environmental conditions. The cell wall was simulated by a viscoelastic model consisting of either four or an infinite number of Maxwell components. Reciprocal of relaxation time for the first component in the former model (1/τ₁) and minimum and maximum relaxation times (T_o and T_m) in the latter, in addition to the stress/strain ratio, were parameters representing cell wall properties. Parameters changed depending on the ages and regions of the coleoptilles used and 011 the environmental conditions under which rice seedlings were grown. Effects on cell wall properties of aeration during submerged growth, excision of the coleoptile tip, and exposure to small doses of red and/or far-red light were examined. In most cases, high values of 1/τ₁ and of T_m and small values of T_o were consistent with the growth potentiality of cells, while the stress/strain ratio seemed to be a consequence of elongation growth.     

APICAL GROWTH OF PROTONEMATA IN ADIANTUM CAPILLUSVENERIS. I. RED FAR-RED REVERSIBLE EFFECT ON GROWTH CESSATION IN THE DARK

Apical growth of individual protonemata in Adiantum capillus-veneris was microphotographically observed before, during and after light treatment. When single-celled protonemata precultured under continuous red light were transferred to darkness, the apical growth continued for the next 24 hr at a rate somewhat slower than that under continuous red light, but the rate significantly decreased thereafter and growth ceased within 72 hr in the dark. The growth in the dark was strongly inhibited by a brief irradiation with far-red light given immediately before the dark period, and the effect of far-red light was fully reversed by subsequent red light. This reversibility was repeatedly observed, suggesting the involvement of a phytochrome system.
The intracellular localization of the phytochrome system in the protonemata was studied, using a narrow-beam irradiator. The results showed that the photoreceptive sites of far-red light are not localized in any particular region of the cell.     

Evidence from mitochondrial genomics supports the lower Mesozoic of South Asia as the time and place of basal divergence of cypriniform fishes (Actinopterygii: Ostariophysi)

We analysed mitochondrial genomic sequences under maximum likelihood (ML) criteria to explore phylogenetic relationships, and performed historical biogeography analysis with divergence time estimation for fishes of Order Cypriniformes (Actinopterygii: Ostariophysi). We added mitogenomes for eight new cypriniforms and one outgroup to a data set comprising 53 and six outgroup mitogenomes from a previous study to make our taxon sampling geographically representative. The ML tree reconfirmed monophyly of four basal cypriniform clades (cyprinids, catostomids, gyrinocheilids, and loaches including balitorids and cobitids). It also recovered 18 monophyletic groups largely equivalent to the subfamilial rank, and resolved interrelationships among most of these subfamilial clades. However, lower bootstrap support for the ML tree and higher approximately unbiased (au) probabilities for alternative topologies around some branches indicated problems that still need to be resolved. Historical taxon biogeography by dispersal‐vicariance analysis, a parsimonious reconstruction of past ranges, and gain‐loss ratio analysis at the subfamilial level, identified the geographical region of basal cypriniform divergence as southern Asia. Bayesian divergence time analysis dated the basal otophysan split, which gave birth to Order Cypriniformes, to the late Triassic around 219.5 Mya. The basal cypriniform divergence took place during the late Jurassic around 155.9 Mya. These dates coincide with the onset and completion, respectively, of the Pangaean breakup. Taking biogeographical analysis and node dating into account, we consider the most likely candidate for the initial geographical range of Order Cypriniformes to be the south‐eastern area of Mesozoic Laurasia (present‐day southern Asia, excluding the Indian subcontinent). We also briefly discuss ecological implications of the group's divergence. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 633–662.