Summary: The azole class of compounds kills fungal cells through an inhibition of ergosterol biosynthesis resulting in malfunction and breakdown of cell membranes. Subinhibitory levels of these compounds were found bringing about a transition from yeast form to pseudohyphal one in Candida tropicalis, as well as ethanol reported previously. The other classes of inhibitors for ergosterol biosynthesis, terbinafine and amorolfin, also caused the transition. These findings implicated the function of ergosterol for filamentous growth. Although depolarized cell growth was observed to precede filamentation during the process of ethanol-induced pseudohyphal formation in this organism, no distinct depolarization was found to occur during the process induced by these antifungal compounds.

View full abstract

Summary: In mesophyll cells of Vallisneria gigantea, an aquatic angiosperm, the intact adhesion of plasma membrane to cell wall at the end walls is indispensable to maintain the stationary arrangement of actin microfilaments.Possible involvements of intracellular actin-binding proteins, transmembrane proteins, and cell wall proteins, in an analogous way to the components located at animal focal contact, in the organization of actin cytoskeleton are discussed.

View full abstract

Summary: The third tubulin, γ-tubulin, is the most general component of microtubule organizing center(MTOC). Many data have been indicating that γ-tubulin has an essential role for the establishment of microtubule(MT)network. Recent studies have also revealed that γ-tubulin in vivo is not monomeric but exists as a constituent of huge protein complex(es). The most famous complex is γ-tubulin-ring complex(γTuRC)in animal cells. We analysed cytoplasmic γ-tubulin of a fungus, Aspergillus nidulans, and revealed that there are divergent γ-tubulin complexes in this organism. Current knowledge about γ-tubulin biogenesis supports the idea that more than one form of γ-tubulin complexes exist in the cells. Divergency is also seen in γ-tubulin itself. The typical example is γ-tubulin of the budding yeast Saccharomyces cerevisiae. In order to clarify the nature of the divergency, we analysed the sequences of other budding yeast γ-tubulins and found that the divegency spreads among the yeasts. Detailed comparison of the sequences, however, indicated a conservative nature of γ-tubulin; the divergent γ-tubulins still preserve the same or similar amino acids important for rtubulin. The analysis also revealed a feature characteristic to the budding yeast γ-tubulins; a number of amino acids conserved uniquely in them seemed to locate in the molecular surface corresponding to the minus-end of tubulin structure. Furthermore, some of the yeast-specific amino acids seemed to be involved in the nuclear localization of the γ-tubulin. In this review, I also discuss divergencies of γ-tubulin and its related proteins as research objects to know the journey of the MT organizer to its functional maturation.

View full abstract

Summary: My survey on a history of Ginkgo both in Japan and China was based on the Japanese and Chinese classical literatures. In China the literatures show that ginkgo started to be cultured in the urban areas in the early10th century and the herbal effects came to be known in the12th century.This plant was first recorded in a Chinese herbal called Shoko-honzo, edited in1159. In Japan the oldest literature which records ‘ginkgoin’ Chinese character is Isei-teikin-ourai edited in about1370. A report written in 1988 says that a sunken ship discovered in the sea near Korea is considered to have been sailing from China for Hakata in Kyusyu, Japan, about 1323. A ginkgo nut was among the relics pulled up from the ship. All the literatures and the discovery of the ginkgo nut in the sunken ship strongly suggests two important points; firstly ginkgo was introduced to Japan by the form of seed and secondly, the seeds were transferred at the period between the late 13th and the early 14th centuries.

View full abstract

Summary: Monophylly is exhibited in Monophyllaea and Streptocarpus(Gesneriaceae).Their plant body consists of a single large cotyledon. They never form stems or foliage leaves through their life history, and they produce inflorescences at the base of the cotyledon laminas. Due to such morphological uniqueness, the monophyllous plants(one-leaf plants)have attracted researchers from among many fields, especially evolutionary morphology. Based on recent data from the comparativemorphogenesis and molecular phylogenetic analyses, the evolution of the monophylly in the Gesneriaceae is discussed.

View full abstract

Summary: The effects of brefeldin A(BFA)on the structure of the Golgi apparatus and the endoplasmic reticulum(ER)and on the thiamine pyrophosphatase activity in these organelles in two green algae, Scenedesmus acutus and Botryococcus braunii, were examined at various stages of the cell cycle, to obtain evidence for the existence of a retrograde transport from the Golgi bodies to the ER. The results demonstrated that a BFA-induced retrograde transport from the Golgi bodies to the ER occurred not only in mammalian cells but also in plant cells.In these two algae, the retrograde transport in the presence of BFA occurred in the interphase cells but not in dividing cells. We further investigated which cytoskeleton participated in this BFA-induced retrogradetransport in S. acutus. The results demonstrate that actin filaments directly mediate the BFA-induced retrograde transport of vesicles. This mechanism differs from that found in mammalian cells, in which microtubules mediate BFA-induced retrograde transport.

View full abstract

Summary: There are many repetitive sequences in the genomes of higher plants. The significance of repetitive sequences and their role in evolution are not clear. I analyzed tandemly arranged repetitive sequences in Rumex acetosa to obtain clues to answer these questions. In R. acetosa, the Y chromosomes are highly heterochromatic and chromosome shape polymorphisms are observed in autosomes and Y chromosomes. I discuss the role of repetitive sequences in the evolution of sex chromosomes and in morphological polymorphism of chromosomes. The morphological changes in autosomes result from an increase or decrease in the number of tandemly arranged repetitive sequences. In the sex chromosomes, specialization of the Y chromosome is promoted by the accumulation of two tandemly arranged repetitive sequences in the process of sex chromosome evolution, The morphological changesin the Y chromosomes result from a rearrangement of the chromosome arms, and do not involve a change in the number of repetitive sequences.

View full abstract

Summary: The non-Mendelian inheritance of organelle genes is a phenomenon that is common to almost all sexual eukaryotes. In the isogamous alga Chlamydomonas reinhardtii, chloroplast(cp)genes are transmitted from the mating type plus(mt+)parent. In this study, the preferential disappearance of fluorescent cp nucleoids of the mating type minus(mt-)parent in living young zygotes was observed. To study the change in cpDNA molecules during this process, the cpDNA of mt+ and mt origin was labeled separately with bacterial aadA gene sequences. Then, a single zygote with or without cp nucleoids was obtained using the optical tweezers, and investigated by nested PCR. This demonstrated the active digestion of mt cpDNA during the preferential disappearance of mt cp nucleoids. To identify factors that cause the active digestion, nuclease activities in C. reinhardtii cells were surveyed. Consequently, a Ca2+-dependent nuclease(NUC-C)that is detected only in mt+ gametes was identified. Further analysis of NUC-C activity in chloroplasts of young zygotes detected NUC-C activity in mt chloroplasts60-90min after mating, which precisely corresponds to the timing of preferential digestion. These results indicate that the maternal nuclease NUC-C is the driving force for the maternal inheritance of cpDNA, which is achieved by the preferential digestion of mt cpDNA in young zygotes.

View full abstract

Summary: The growth of leaves is dependent on the extent of the expansion of leaf cells and on cell proliferation. The rates of the division and enlargement of leaf cells at each stage contribute to the final shape of the leaf, and play important roles throughout leaf development. However, the processes controlling these basic aspects of leaf development remain unresolved. Recently, we identified and characterized several genes that regulate leaf expansion. This brief review article focuses on our current study of the genetic mechanisms of leaf expansion in Arabidopsis.

View full abstract