Summary: We tested the fbrmation of malfbrmed plantlets that are usually fbund during mass propagation in Phalaenopsis alliance(including Doritaenopsis). When 75 normal and malfbrmed sections of protocorm-like-bodies(PLB)of Doritaenopsis City Girl were cultured in vitro for mass propagation, 1.7%and100% of malfbrmed plantlets were formed respectively, Cytometric analysis revealed that the malfbrmed plantlets had double the nuclear DNA content in comparison to normal ones. They were 8C and 4C amounts in comparison with the 2C internal standard of Phalaenopsis schilleriana. Malformed plantlets also showed larger nuclei than normal ones in apical meristems of root tips and in the epidermis of PLB and leaves in 4, 6-diamidino-2-phenylindole(DAPI)-stained sections. Analyses by light microscopy and confocal laser microscopy suggested that the formation of malfbrmed PLB was possibly due to changes of 4C cells to8C cells in the epidermis.

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Summary: Rice leaf is strap-shaped but shows a complicated structure polarized along the three leaf axes. Leaf shape of grass is roughly determined during the process of leaf founder cell recruitment in the shoot apical meristem(SAM). Accordingly, to elucidate the mechanism of leaf founder cell determination in the SAM is important for a better understanding of leaf development in grass. shoot organization(sho)mutants produce thread-like leaves in the early vegetative phase. The expression pattern of OSHI, a marker of indeterminate cells in the SAM, revealed that a large number of leaf founder cells exits in sho SAM despite the production of narrow leaves. In addition, the variety of leaf phenotype in sho leaves is caused by an unsynchronous growth among leaf domains along the central-marginal axes, suggesting these domains are regulated independently. The phenotypes of sho are very similar to those of weak shootless(shl)mutants showing shoot-less phenotype in the embryo. It is considered that both SHO and SHL genes are important regulators for SAM maintenance and early leaf development in rice.

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Sumary: Higher plants develop species-specific architectures by continuously generating lateral structures such as leaves and flowers from the shoot apical meristem post-embryonically. Their primordia are generated with phyllotactic patterns of species-specific manner and develop autonomously from the shoot apical meristem. In addition, axillary shoots, which form in the axils of leaves develop autonomously from the main axis and affect the final architecture of a plant. The variations of different developmental patterns in these lateral structures give rise to a variety of plant morphology. In this review, we focus on molecular mechanisms that regulate development of lateral structures.

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Summary: The ASYMMETRIC LEAVES1(AS1)and ASYMMETRIC LEAVES2(AS2)genes of Arabidopsis thaliana are involved in the establishment of the leaf venation system, which includes the prominent midvein; as well as in the development of a symmetric flat lamina. Both AS1 and AS2 genes are involved in repression of class1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats(Cmotif), a conserved glycine residue, and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results further suggest that AS2 functions to regulate the formation of a flat leaf lamina in the presence of the AS1 gene.

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Summary: Recent molecular phylogenetic studies are rapidly and drastically changing systems of classification, which had long developed by the progress of morphological studies. Notably, it has become clear that Arnborella is the basalmost genus in angiosperm evolution, followed by the divergent of Nymphaeales and Illiciales. Monocotyledons are derived from the subsequently diverged clade called eumagnollids. Based on phylogenetic trees, we now can try studies on character evolution starting from the basalmost plant group toward derived ones. On the other hand, some higher taxa like“Liliaceae”, “Euphorbiaceae”, and“Flacourtiaceae” are split into two or many more segregates that may be positioned as separate families or assigned to already known families. Many such families with additional genera or losing genera need critical morphological studies for revision of their respective circumscriptions.

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Summary: The human pathogenic fungus Candida albicans has traditionally been classified as a diploid, asexual organism. In 1986, a phenomenon of ploidy shift was described by the author in this organism. A clinical isolate NUM51 contained both diploid and tetraploid cells and an electron microscopy of the culture showed that some diploid cells seemed to be undergoing endomitosis to shift up their ploidy level from diploid to tetraploid, while some tetraploids showed nuclear structures similar to those of meiosis II in S. cerevisiae, suggesting the occurrence of reductional nuclear division to shift down from tetraploid to diploid. The phenotype of these strains executing the ploidy-shift was named Sps-. Both high frequency of the occurrence of chromosome reorganization and of the loss of heterozygosity were found due to the existence of high-ploidy cells in the cell population of the C. albicans Sps-strains. Recently, a set of C. albicans MTL genes has been identified that corresponds to the master sexual cycle regulators al, alphal, and alpha2 of the Saccharomyces cerevisiae mating-type(MAT)locus and mating-competent forms of the organism were recently described that produced tetraploid mating products. The Sps-strain NUM51 was found heterozygous for the two mating types MTLa and MTLx by colony-PCR. When mutant strains containing only MTLx were constructed by the loss of one homolog of chromosome 5, such strains no longer showed the occurrence of ploidy shift. This finding suggests that the ploidy shift may be under the control of the heterozygous MTLa/MTLx locus.

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Complex, mobile spherical structures continuous with the vacuolar limiting membrane were identified in young cotyledons of Arabidopsis by expression of a vacuolar membrane marker(r-TIP-GFP)and by electron microscopy, and were named“bulbs”. These structures are cytoplasm wrapped by two layers of intricately folded membrane; both layers are continuous with the vacuolar limiting membrane. When visualized using r-TIP-GFP, the fluorescence intensity of bulbs is about3-fold higher than that of the vacuolar limiting membrane. However, bulbs were negative for GFP-AtRab75, another vacuolar marker. These results suggest that bulbs form a subregion in the continuous vacuolar membrane that concentrate some proteins and segregate others.

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Summary: This review describes phenomena that are common and unique to organell differentiation during male gametophyte development: (1)selective decreases/increases in plastid and mitochondrial DNA in generative cells just after pollen mitosis one. (PMI), which determine the mode of cytoplasmic inheritance; (2)the unique distribution of mitochondria, which surround the nuclear envelope in a single compact layer, just before and after PMI in Pharbitis nil; (3)the role of CSL1, a novel nuclear protein, in controlling vacuole contraction before and after PMI; and(4)tapetosome differentiation in tapetal cells depending on the sterol content under the control ofHMG1, a key enzyme in the cytosolic isoprenoid biosynthesis pathway in higher plants.

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Summary: Pyrenoids are electron-dense bodies found in the chloroplast stroma in most eukaryotic algae. The matrix of the pyrenoids consists mainly of Rubisco(ribulose1, 5-bisphosphate carboxylase/oxygenase), a CO2-fixing enzyme in photosynthesis. Green algal genus Chloromonas is traditionally distinguished from Chlamydomonas by the absence of pyrenoids, but molecular phylogenetic studies demonstrated that Chloromonas and several species of Chlamydomonas constitute a closely related group“Chloromonas lineage”. In this lineage, various ultrastructural types of pyrenoids are present and these morphological differences are associated with the degree of inorganic carbon concentration inside the cells, which is related to the CO2-concentrating mechanism(a mechanism for increasing photosynthetic affinity for CO2). Analysis of rbcL(Rubisco large subunit)gene sequences of Chloromonas lineage and 45 other green algae showed that the proteins encoded by the rbcL genes have a much higher level of amino acid substitution in members of Chloromonas lineage than they did in other algae. Amino acid residues at the antra-dimer interface of Rubisco large subunit have an especially higher level of amino acid substitution. These kinds of specific substitutions were not observed in the proteins encoded by other chloroplast genes that we analyzed: atpB and psaB.

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