Koichi Uehara

Vegetative diversification and radiation in subtribeDendrobiinae (Orchidaceae): Evidence from chloroplast DNA phylogeny and anatomical characters

The data derived from a chloroplast DNA restriction site analysis of subtribeDendrobiinae (Orchidaceae) indicate that extreme vegetative diversification is concentrated in two limited parts of this group. Overlaying the vegetative character states onto the chloroplast DNA cladogram suggests that several xeromorphic, vegetative characters evolved in the lines leading to the above-mentioned clades. Several anatomical characters are also associated with xeromorphy. These vegetative and anatomical characters facilitated the establishment of this group in various dry habitats. On the other hand, the modifications of size and number of parenchymatous cells substantially contributed to the vegetative diversification. This fact implies that a simple structural adjustment can result in a major modification of growth habits in theDendrobiinae.

Pollen wall development in Cryptomeria japonica (Taxodiaceae).

Pollen wall development in Cryptomeria japonica was observed by scanning and transmission electron microscopy. The pollen of C. japonica is characterized by a non-saccate, projecting papilla. The exine of C. japonica consists of the outer granular ectexine and the inner lamellated endexine. At the tetrad stage, the initial granular layer of the pro-ectexine first forms on the microspore plasma membrane. The tripartite lamellae of the pro-endexine form under the pro-ectexine. The prosporopollenin material is deposited on the pro-ectexine and pro-endexine at the free spore stage. The ectexine granule increases its volume and the endexine lamellae thicken. The papilla protrudes during the tetrad stage. The tip of the papilla bends laterally where the exine is thinner. Exine construction in C. japonica is similar to that of Cunninghamia; however, the amount and size of the granular ectexine and lamellated endexine differ. The conspicuous papilla protrudes and bends during the tetrad period.

Characterization, Occurrence, and Molecular Cloning of a Lectin from Grifola frondosa: Jacalin-Related Lectin of Fungal Origin

A lectin named GFL was isolated from the fruiting body of the basidiomycete mushroom Grifola frondosa, which belongs to Aphyllophorales. The lectin had a molecular mass of 24 kDa on SDS–PAGE. The hemagglutinating activity of GFL was not inhibited by any monosaccharide, and inhibited only by porcine stomach mucin so far as tested. The occurrence of GFL was studied at three stages during fruiting body formation. The largest quantity of hemagglutinating activity was found in the fruiting body, and lesser amounts in the mycelial mat and the primordium. The 24-kDa band of GFL was found at all three stages, and the band-intensity corresponded to the level of activity in each sample. By cloning and sequencing the GFL-cDNA, the primary structure of this lectin was determined. GFL is composed of 181 amino acids, having no signal peptide. The amino acid sequence was found to be homologous to those of so-called jacalin-related plant lectins, suggesting that GFL is the first example of a jacalin-related lectin of fungal origin.

Molecular properties of mycelial aggregate-specific lectin of Pleurotus cornucopiae.

By cloning and sequencing cDNA, the primary structure of a mycelial aggregate-specific lectin of Pleurotus cornucopiae was determined. The amino acid sequence was novel and elucidated unique properties of this lectin: It was composed of 373 amino acids, 33 of which constitute a signal sequence. The sequence of the mature lectin consisted of two homologous regions having five glycosylation recognition signals and six cysteine residues. However, the distribution of these elements in the two regions was biased. Expression of cDNA in Escherichia coli and Pichia pastoris revealed the requirement of glycosylation to produce the functional lectin. Gel filtration followed by gel electrophoretic analyses of the purified lectin showed that the active component moved faster than the bulk of the protein, suggesting that the most active lectin formed an oligomer of subunits through disulfide bonds. From these observations, a model for the structure of the active form of this lectin is proposed. Southern hybridization using the cDNA as a probe revealed the presence of several genes. The lectin gene was composed of five exons and five introns.

Pollen morphology of andruris japonica (triuridaceae)

Abstract Pollen morphology of Andruris japonica (Triuridaceae) was investigated by light and electron microscopy. The pollen is monosulcate and has a size of 22–25 μm × 25–28 μm in polar view. In the non-apertural region the exine has gemmate to nearly verrucate protrusions of 0.4–0.5 μm in diameter and 0.3–0.5 μm in height, and a foot layer of 0.4–0.5 μm in thickness. The sporoderm of the apertural region has large gemmae of 0.7–0.8 μm in diameter and 0.6–0.7 μm in height, with a thin foot layer of 0.1 μm thickness.

Development and characterization of EST‐SSR markers for the genus Rhododendron section Brachycalyx (Ericaceae)

Simple sequence repeat (SSR) markers were developed from expressed sequence tags (ESTs) for Rhododendron section Brachycalyx in order to elucidate its evolutionary processes and reproductive ecology. Nineteen polymorphic EST-SSR markers were developed from EST libraries of R. amagianum and R. hyugaense. Polymorphisms for these markers were assessed using four species of section Brachycalyx. The number of alleles ranged from 1 to 14, and the observed and expected heterozygosity ranged from 0.000 to 0.931 and 0.000 to 0.904, respectively. The EST-SSR markers developed in this study will be useful for elucidating population genetic structure and breeding systems in section Brachycalyx.

Development of megaspores and microspores in Isoetes japonica A. Br. (Lycopodiophyta: Isoetaceae)

Abstract Microspore and megaspore development in Isoetes japonica was studied using light, scanning electron and transmission electron microscopy. Differences in cytokinesis following meiosis result in monolete microspores with bilateral symmetry, and trilete megaspores with radial symmetry. Wall development follows essentially the same sequence in both microspores and megaspores, but with the wall of the latter being very much thicker. A significant difference was observed in the tetrad stage, when microspores have an essentially rounded outline with the plasma membrane folded into a crest at the site of the future aperture. Megaspores in the tetrad stage are strongly invaginated over their entire surface, creating numerous crests, and this appears to have a role in determining the morphology of the perispore. The outline shape of the megaspore perispore having been established in the tetrad stage, most of its substance is added later and is derived from the degenerating tapetum.

Pollen wall development in Sciadopitys verticillata (Sciadopityaceae)

Pollen wall development of Sciadopitys verticillata was observed by transmission electron microscopy. The pollen of S. verticillata is non-saccate and spherical, and the exine consists of the outer thick, sculptured ectexine and the inner lamellated endexine. At the early tetrad stage, the initial ectexine and lamellae of the initial endexine begin to form on the microspore plasma membrane. The ectexine granules gradually swell. Deposition of sporopollenin materials on the ectexine granules then results it their becoming partially connected to each other. Identification of the original small ectexine granules then becomes difficult, and, finally, the ectexine appears as a homogeneous, partially discontinuous layer. The granules of the early ectexine cannot be identified. At maturity, there are four to five endexine lamellae. Recent molecular data have shown that Sciadopitys first branches off from the Cupressaceae plus Taxaceae clade, which is characterized by granular exine. Although the ectexine of Sciadopitys is similar to that of the Cupressaceae during initial development, the morphology of the ectexine is significantly different in the mature pollen. The initial stage of pollen development clearly shows the structural homology of the granular ectexine. Divergence of the exine structure occurs in the later stages.

Phylogeographic analysis suggests two origins for the riparian azalea Rhododendron indicum (L.) Sweet

Ecological speciation is an important factor in the diversification of plants. The distribution of the woody species Rhododendron indicum, which grows along rivers and is able to withstand water flow when rivers flood (i.e. it is a rheophyte), is disjunct, in contrast to the widespread distribution of its relative, Rhododendron kaempferi. This study aimed to elucidate the phylogenetic relationships between R. indicum and R. kaempferi and the evolutionary processes that gave rise to them. The sequences of three non-coding chloroplast DNA regions (total length 1977 bp) were obtained from 21 populations covering the ranges of the two species. In addition, genome-wide SNPs were genotyped from 20 populations using a genotyping by sequencing method. Leaf morphologies were measured for eight representative populations. Two chloroplast DNA haplotypes, which were detected in R. indicum, were shared between the two species. Genome-wide SNPs identified two lineages in R. indicum and these lineages did not constitute a monophyletic group. Each of these two lineages was related to geographically close populations of R. kaempferi. Leaf morphology, which is a characteristic feature in rheophytes, was not differentiated between the two lineages in R. indicum. The morphological similarity between the two heterogeneous lineages may be a result of parallel evolution from R. kaempferi or of introgressive hybridization between the species due to strong selective pressure imposed by flooding.