Summary:With the completion of the rice genome sequencing project, the next major challenge is the systematic determination of gene function, then difficulties arise in the identification of a phenotype quantitatively that can be associated with the mutation. Here we overview the trend in image technology and its application for the phenotypic analysis process. We introduce our attempts to measure various parameters based on a series of growth images collected by newly developed automatic imaging system. First, the detailed measurement of leaf length in rice seedlings was carried out and presented. Second, the rice lamina inclination process was continuously analyzed and the effects of plant hormone and light on this response were discussed. Third, the leaf area of Arabidopsis thaliana was continuously measured, and a circadian rhythm of leaf movements was identified. We would like to discuss future aspects of image analysis and related technology for a complete understanding of a gene's function that will be realized only when genomic information can be associated with a phenotype at the organismal level.

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Summary: In plant cells, various kinds of cytoplasmic particles exhibit active intracellular movements. To elucidate the regulatory mechanism for these movements, several approaches have been developed to visualize and quantitatively analyze the movements. Recently, using infrared microscopy and dynamic image processing technique, we have investigated the light-dependent cytoplasmic motility in Vallisneria gigantea epidermal cells. The cytoplasmic motility is an actin-dependent process and regulated by type II phytochrome. Moreover, the induction of cytoplasmic motility occurs in a few seconds of light irradiation, and in a subcellularly localized manner.

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Summary: To determine how, where and when nano-machines and/or nano-systems act within cells is necessary for understanding life phenomena. To analyze the cellular structure at nano level, electron microscope is necessary. However, until recently, the analysis of cellular structure by electron microscopy has been limited by both specimen preparation method and by image analysis problems. Both of these limitations can be overcome by combining cryofixation methods in conjunction with electron tomography. In this lecture, we will describe the history and the method of electron tomography.

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Summary: Though plant meiotic mutants have been isolated and analyzed for along time, molecular analyses of plant meiosis have practically begun when new technologies, transposon or T-DNA tagging methods, became available for such area of plant researches. By these methods, many meiotic tagged mutants were isolatedfrom Arabidopsis and other plants. At the same time, recent cytological methods, such as FISH(fluorescence in situ hybridization)and fluorescent immunohistochemistry, provided more specific analyses of meiotic mutants, which enabled us to study chromosome behavior and protein localization during meiosis in detail. Along with accumulation of knowledge about meiosis of different organisms, combined application of the two techniques has accelerated the progress of plant meiosis research since 1998. In this paper, concentrating on the tagged mutants of meiosis and their analytical methods, recent results of plant meiosis study will be summarized.

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Summary: Mitochondrial DNA(mtDNA)is packed into highly organized structures called mitochondrial nucleoids(mt-nucleoids). We identified and characterized a new mitochondrial histone-like protein, termed Glom(a protein inducing agglomeration of mitochondrial chromosome), from highly condensed mt-nucleoids of the true slime mold, Physarum polycephalum. This protein has a lysine-rich region with proline-rich domain in the N-terminal half and two HMG boxes in C-terminal half. Glom induced intensive DNA condensation without suppressing replication and transcription. The lysine-rich region was sufficient for the mtDNA condensation and the proline-rich domain was essential to keep those genetic activities. The expression of Glom also complemented the E.coli mutant lacking the bacterial histone-like protein HU and the HMG-boxes region of Glom was important for the complementation.

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Summary: γ-Tubulin is a protein associated with microtubule organizing centers(MTOCs)such as centrosomes in animal cells. Although seed plants have γ-tubulin, they do not have discrete MTOCs comparable to centrosomes, and organization of the multiple microtubule arrays in plants has been enigmatic. Because basal land plants have an exceptional variety of unique morphologically discrete MTOCs(e. g. centrosome, polar organizer, plastid-based quadripolar microtubule system), microtubule systems in basal land plants may hold clues to evolutionary changes in γ-tubulin localization and function in evolution of acentriolar spindles in plants. In the present study, we isolated and characterized a genomic clone encoding γ-tubulin of a liverwort(Bryophyta)and verified the localization of γ-tubulin on several types of discrete MTOCs in bryophytes using the G9 anti-γ-tubulin antibody that recognized ca. 55kDa peptide of bryophytes. We also describe changes in the localization of γ-tubulin closely correlated with the MTOC cycle in meiosis of the liverwort, Dumortiera hirsuta. γ-Tubulin is detectable on the surface of isolated plastids and nuclei and microtubules can be repolymerized from the isolated plastids. γ-Tubulin localization on plastid and nuclear surfaces are not affected by destruction of microtubules by oryzalin. From these results, we conclude that γ-tubulin is a highly conserved protein associated with microtubule nucleation in basal land plants, and it has cell cycle dependent manner essential for the orderly succession of microtubule arrays.

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Summary: Many lower land plants have cells that contain a single plastid. A monoplastidic condition is observed in dividing vegetative cells of hornworts, the moss Takakia, and some microphyllophytes(Isoetes and Selaginella). Sporogenous cells and sporocytes are monoplastidic in all mosses, hornworts, Isoetes and Selaginella, as well as some species of liverworts, Lycopodium and Angiopteris. Additionally, spermatocytes in the taxa mentioned above are typically monoplastidic. In monoplastidic cells, the single plastid divides before nuclear division and divided plastids seem to serve as microtubule organizing centers of mitotic apparatus. Such a monoplastidic condition is considered to be a critical symplesiomorphy among bryophytes, lycopsid pteridophytes, and the coleochaetalean algae. In this paper, we summarize the results of recent investigations on monoplastidic cells of lower land plants.

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Summary: Permineralization is a peculiar process of fossilization preserving anatomical details of plants of the Past, in some cases with a remarkable condition as represented by motile sperm in an Permian ovule. Here I introduce selected studies on permineralized plant remains emphasizing their importance in plant morphological studies to various extent. Ferns from the Eocene Princeton Chert Bed, Canada, Late Cretaceous plants from Japan, and a megasporangiate organ of Late Permian Glossopteris from Australia are mentioned.

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Summery: The origin of the outer integument, which is one of the prominent synapomorphies of angiosperms, was inferred to explore the phylogenetic origin of the angiosperms. Studies based on the ovules of“ANITA”, a group of early-diverged families, revealed that the ovules with the cup-shaped outer integument are derived from the ovules with hood-shaped outer integument. The morphological marker in the seed was sought for from which the outer integument morphology could be inferred because the seeds with more fossilized potential than flowers would be helpful in deducing the primitive morphology of the outer integument based on the fossil records. As a result, I found that the relative position of the micropyle to the hilum could be used as the marker for inferring the outer integument morphology(i. e., hood-shaped or cup-shaped). Based on this marker, it is inferred that the oldest seed fossils of angiosperms are derived from the ovules with the hood-shaped outer integument. Neo- and Paleo- botanical data suggests that the hood-shaped outer integument with bilateral symmetry is primitive. The bilaterally symmetrical nature is one of the characteristics of the leaf, thus the outer integument could be homologous to the leaf. Further to examine this hypothesis I analyzed the expression pattern of INO homologue of Nymphaea alba as molecular marker for the dorsiventrality. INO homologue was limitedly expressed in the outer epidermis of the outer integument, suggesting that the outer integument has the dorsiventrality. These results imply that the outer integument is derived from the leaf.In addition to this, the carpel is suggested to be homologous to sporophyll, thus the gynoecium of angiosperms is compared to the unitegmic orthotropous ovule enclosed in two leaf-like organs, which is known in some groups of the seed ferns.

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