Analysis of binding of biotinylated protoplast-release-inducing protein that induces release of gametic protoplasts in the Closterium peracerosum-strigosum-littorale complex

A protoplast-release-inducing protein (PR-IP) which is released from mating-type plus (mt⁺) cells and induces the release of gametic protoplasts from matingtype minus (mt⁻) cells of Closterium was biotinylated and then used to examine the interaction of this protein with mt⁻ cells. The protoplast-release-inducing activity of PR-IP was not altered after the biotinylation. When mt⁻ cells that had been pre-cultured for 24 h were incubated with biotinylated PR-IP for 6 h in nitrogen-deficient medium that contained 1% (w/v) bovine serum albumin, and then washed with the same medium, only a 19-kDa polypeptide, the smaller subunit of PR-IP, was detected in cells by the avidin and biotinylated horseradish-peroxidase macromolecular complex system. The amount of bound 19-kDa polypeptide increased with increasing doses of PR-IP and reached a maximum at around 10 nM, reflecting the protoplast-release-inducing activity. From a Scatchard plot, the dissociation constant of the polypeptide was calculated to be 2.7 · 10⁻⁸ M. The binding of the polypeptide proceeded only after an appropriate period of pre-culture in the light, and the polypeptide was competitively displaced by non-biotinylated PR-IP. From these results, it appears that the PR-IP induces the release of protoplasts from mt⁻ cells by binding of a polypeptide of relative molecular mass 19000 to the receptor on the cell surface in a manner analogous to the binding of peptide hormones in animals.     

ANALYSIS OF GAMETIC PROTOPLAST RELEASE IN THE CLOSTERIUM PERACEROSUM-STRIGOSUM-LITTORALE COMPLEX (CHLOROPHYTA)1

A biologically active glycoprotein (protoplast-release-inducing protein; PR-IP), which induces the release of gametic protoplasts from mating type minus (mt^-) cells of the Closterium peracerosum-strigosum-littorale complex, was prepared from a medium in which mt^- and mt⁺ cells had been previously incubated together. The process of PR-IP-inducing protoplast release was analyzed. Induction of protoplast release was dependent upon the duration of both PR-IP treatment and preincubation in nitrogen-deficient mating medium before PR-IP treatment. Low cell density in the preculture stage had a significant stimulative effect upon the induction of protoplast release. Light was necessary for protoplast release, especially just before PR-IP treatment. Chloramphenicol and 3-(4-chlorophenyl)-1,1-dimethylurea (CMU) exerted inhibitory effects on protoplast release, especially when they were applied to the preculture stage but not when they were applied to the protoplast-releasing stage after the PR-IP treatment. We suggest that preculture at a low cell density under continuous light conditions that may cause metabolic changes in the chloroplast is a very important stage for gametic protoplast release in this Closterium.     

Production and secretion of a biologically active Closterium sex pheromone by Saccharomyces cerevisiae

The cDNA fragment coding for the Closterium sex pheromone (protoplast-release-inducing protein inducer, PR-IP inducer) was inserted into a Saccharomyces cerevisiae–Escherichia coli shuttle vector, under the control of the glucose-repressible alcohol dehydrogenase (ADH2) promoter of yeast. The yeast cells transformed by this construct produced and secreted recombinant PR-IP inducer into the surrounding culture medium. The release of PR-IP from mt⁺ cells was induced by the recombinant pheromone, whereas amino- and carboxy-terminal truncated forms did not show any biological activity. High levels of asparagine-linked glycosylation in the recombinant pheromone were also confirmed after the treatment by deglycosylation enzymes.     

甜菜夜蛾几丁质合成酶基因A和B启动子的克隆

几丁质不仅是昆虫的表皮和围食膜的主要成分,也是一个非常关键的害虫控制靶标,主要通过几丁质合成酶（chitin synthase,CHS）基因合成。本文在克隆甜菜夜蛾Spodoptera exigua的两个几丁质合成酶基因（SeCHSA和SeCHSB）cDNA和基因组序列的基础上,从基因的5′末端设计特异性引物和构建特定的基因组文库, 采用PCR的方法获得了5′端侧翼序列。通过5′RACE的方法确定SeCHSA和SeCHSB基因的转录起始位点后,获到了启动子序列。这为研究昆虫几丁质合成和转录调控奠定了基础。     

Sexual reproduction and sex determination in green algae

The sexual reproductive processes of some representative freshwater green algae are reviewed. Chlamydomonas reinhardtii is a unicellular volvocine alga having two mating types: mating type plus (mt⁺) and mating type minus (mt^?), which are controlled by a single, complex mating-type locus. Sexual adhesion between the gametes is mediated by sex-specific agglutinin molecules on their flagellar membranes. Cell fusion is initiated by an adhesive interaction between the mt⁺ and mt^? mating structures, followed by localized membrane fusion. The loci of sex-limited genes and the conformation of sex-determining regions have been rearranged during the evolution of volvocine algae; however, the essential function of the sex-determining genes of the isogamous unicellular Chlamydomonas reinhardtii is conserved in the multicellular oogamous Volvox carteri. The sexual reproduction of the unicellular charophycean alga, Closterium peracerosum-strigosum-littorale complex, is also focused on here. The sexual reproductive processes of heterothallic strains are controlled by two multifunctional sex pheromones, PR-IP and PR-IP Inducer, which independently promote multiple steps in conjugation at the appropriate times through different induction mechanisms. The molecules involved in sexual reproduction and sex determination have also been characterized.