Two Amino-acid Carriers in Pea Chloroplasts

CHLOROPLASTS are more permeable to amino-acids^1,2 than are cell membranes³ and also discriminate between their optical isomers². This has led to the suggestion that the passage of amino-acids through the limiting membranes of chloroplasts is facilitated by carriers². Using the additional criteria of saturation and competition, we support this suggestion and show that at least two carriers are probably involved.     

Carbohydrate Partitioning and Compartmental Analysis for a Highly Productive CAM Plant, Opuntia ficus-indica

Carbon partitioning patterns of Opuntia ficus-indica, a widelycultivated crassulacean acid metabolism species, were analysedto estimate carbon fluxes. After labelling a cladode with ¹⁴CO₂,activities of ¹⁴C in various organs were measured for 6 weeks;the observed ¹⁴C time-courses for ¹⁴C in the labelled cladodeand for transfer into other organs were simulated with a compartmentmodel. Within the first week, half of the newly synthesizedcarbohydrate in the labelled cladode was either converted intostructural material in that cladode, lost by respiration ofthat cladode, or moved to other organs. In the non-labelledcladode and the roots, such newly synthesized carbohydrate initiallyincreased, reached maxima, and then declined. The basal cladodeand the daughter cladode used 65 and 96%, respectively, of theirown assimilate. Roots imported 12 and 2 % of carbohydrate fromthe basal cladode and the daughter cladode, respectively. Whenthe whole plant was shaded, the daughter cladode incorporatednearly threefold more carbohydrate from the basal cladode intostructural material compared with the control. When plants weredroughted, roots incorporated 23 % more and the daughter cladodeincorporated 68 % less carbohydrate from the basal cladode intotheir structural material than for the control. The basal cladodesof the 18-month-old plants exported 60% more carbon than thoseof the 6-month-old plants. Carbon flux rates derived from compartmentalanalysis can be used as parameter values in plant productionmodels. Carbon partitioning, compartment model, drought, plant age, shading     

Autotropism in Fungal Spores

Autotropism was examined in germinating spore pairs of Rhizopusstolonifer, Mucor plumbeus, Trichoderma viride, and Botrytiscinerea. When germinated on agar surfaces the first three speciesexhibited negative autotropism, B. cinerea being neutral inits autotropic behaviour. More pronounced negative autotropismwas shown by the first three species when germinated on a filmof Cellophane applied to an agar surface. Under these conditionsB. cinerea displayed positive autotropism. Spore pairs of R. stolonifer germinated on agar containing cellulosepowder or charcoal showed less negative autotropism than onagar alone. Touching spore pairs of each species showed a markedtendency towards cis-ness, i.e. germ-tubes beginning on thesame side of a line joining the two spore centres, under theculture conditions described, the one exception being the reductionin cis-ness recorded when R. stolonifer was germinated on agarcontaining charcoal. Time courses of germination were determined for single sporesand touching spore pairs of R. stolonifer and M. plumbeus anda significant promotion was obtained in the spore pairs as comparedwith the single spores. Although both these species exhibitmarked negative autotropism there was a strong tendency forthe positive germ-tube, i.e. one beginning more nearly towardsits neighbour, to emerge before the negative germ-tube in thosespore pairs having one germtube positive and the other negativein orientation. Also, in R. stolonifer, the replacement of germination-promotersby germination-inhibitors in filtrates from spore suspensionsas they age is correlated with a change from positive to negativeautotropism in germinating members of (+ –) spore pairs. Possible mechanisms are discussed to account for the observedeffects.     

Eleven new highly polymorphic microsatellite loci in the yellow croaker,Pseudosciaena crocea

We developed 11 new microsatellite markers in Pseudosciaena crocea by screening an enriched genomic library using nonradioactive polymerase chain reaction (PCR) techniques. All loci were found to be polymorphic with an average of 14.9 alleles per locus (range four to 30). The mean observed and expected heterozygosities were 0.86 (range 0.57–1.00) and 0.90 (range 0.62–0.98), respectively. Four loci showed significant Hardy–Weinberg disequilibrium. The high variabilities revealed in this study suggest that these microsatellite loci should provide useful markers for population genetic studies of P. crocea.     

Receptors for the neuropeptides,myoinhibitory peptide and SIFamide,in control of the salivary glands of the blacklegged tick Ixodes scapularis

Tick salivary glands are important organs that enable the hematophagous feeding of the tick. We previously described the innervation of the salivary gland acini types II and III by a pair of protocerebral salivary gland neurons that produce both myoinhibitory peptide (MIP) and SIFamide (?imo et al., 2009b). In this study we identified authentic receptors expressed in the salivary glands for these neuropeptides. Homology-based searches for these receptors in the Ixodes scapularis genome sequence were followed by gene cloning and functional expression of the receptors. Both receptors were activated by low nanomolar concentrations of their respective ligands. The temporal expression patterns of the two ligands and their respective receptors suggest that the SIFamide signaling system pre-exists in unfed salivary glands, while the MIP system is activated upon initiation of feeding. Immunoreactivity for the SIFamide receptor in the salivary gland was detected in acini types II and III, surrounding the acinar valve and extending to the basal region of the acinar lumen. The location of the SIFamide receptor in the salivary glands suggests three potential target cell types and their probable functions: myoepithelial cell that may function in the contraction of the acini and/or the control of the valve; large, basally located dopaminergic granular cells for regulation of paracrine dopamine; and neck cells that may be involved in the control of the acinar duct and its valve.     

Lanzia berggrenii及其相关种的系统发育地位(英文)

系统发育分析结果表明,尽管Lanzia berggrenii能在寄主中形成基物子座,但与膜盘菌属的核心种关系较近,而与蜡盘菌科成员关系较远,应该归属于膜盘菌属。在广义的膜盘菌属的系统树中该种及在新西兰发现的4个新种构成一个单系群,分别命名为Hymenoscyphus haasticus,H. kiko,H.ohakune和H.waikaia。它们的共同特征:基物均为南青冈叶片,侧丝顶端分枝形成类似囊层被的结构,覆盖于子实层上部。Lanzia berggrenii var.metrosideri应为膜盘菌属中一个独立的种,即Hymenoscyphus metrosideri。