Genetic Regulation of Melanocyte Differentiation

Melanocytes originate from the neural crest in vertebrates and migrate to the body surface where they differentiate into functional cells. Genes involved in melanocyte differentiation can be classified into two groups. One of them consists of the functional genes that control proteins specific to the function of the melanocyte. As the representative gene of this category, albino (c) locus in the mouse is considered to control tyrosinase, the key enzyme in melanogenesis. cDNA for mouse tyrosinase has been cloned and sequenced. The cDNA can be used to detect tyrosinase mRNA synthesized during melanocyte differentiation. On the other hand, genes such as brown (b) or pink-eyed dilution (p) have been assumed to control melanosome proteins. The other category consists of genes that regulate the expression of these functional genes directly or indirectly. In the mouse, so-called white-spotting genes and genes of the agouti series are considered to fall into this category. Based on the fact that mutations at the white-spotting loci result in the absence of melanocytes in a particular area of skin, it is assumed that some of these loci control the factors that promote either differentiation or migration of melanoblasts and are candidates for the classic regulator genes Genes at the agouti (a) locus in the mouse determine the type of melanin synthesized in hair follicle melanocytes, that is eumelanin or pheomelanin. An interesting feature of this locus is that the site of gene action is not within the melanocytes but in the cells surrounding them. The results of our study indicate that the gene product of the a-locus interacts with α-MSH at the α-MSH receptor site, regulates the cellular cAMP level via a signal transduction system and, in turn, determines the type of melanin synthesized in the cells.     

EFFECT OF LIGHT ON AUXIN TRANSPORT AND ELONGATION OF AVENA MESOCOTYL

The present work was undertaken to find if there are relations between light and auxin action on elongation of coleoptilar node and mesocotyl with Avena seedlings. Red light inhibited the elongation of mesocotyl and simultaneously decreased the rate of transport of diffusible auxin through the node. Red light also inhibited the transport of exogenously given IAA through the nodal region. The light inhibition of IAA transport was closely related to the increase of IAA immobilization. As the age proceeds, the ability of IAA immobilization increased with the decrease in the rate of mesocotyl elongation, even if the seedling was grown in complete darkness. The nature of radioactive substances found in the IAA-C¹⁴ treated tissue was examined by paper chromatography. The above results strongly suggested that the increase of IAA immobilization might result in the inhibition of mesocotyl elongation.     

Differential fluorescent-banding patterns in chromosomes of four species of Cycas (Gycadaceae)

Similar karyotypes of In = 22 in Cycas circinalis, C. media var. basaltica, C. revoluia var. rewluta, C. revoluta var. taiwaniana and C. siammsis were compared with each other by using the CMA and DAPI fluorescent staining methods. Their four largest submedian-centromeric chromosomes each had a CMA band at the terminal region in common. Their 12 terminal-centromeric chromosomes commonly displayed CMA bands at the terminal region and the pericentric region. Two of the 12 terminal-centromeric chromosomes carried a CMA band somewhere in the interstitial region of the long arm. C. circinalis alone showed it at a relative position closer to the centromere. The other taxa showed it at a relative position near the terminal region. All of the chromosomes exhibited the DAPI dot at the centromeric region.     

金花茶花药愈伤组织的体细胞减数分裂

金花茶(Camellia petelotii)的小孢子单核期花药,经培养和继代培养6个月后的愈伤组织中,发现有少量体细胞进行减数分裂。在减数第一和第二次分裂中,同源染色体的配对和分离基本正常,最后形成四分体。该愈伤组织经石蜡切片和压片观察,发现其主要由大量的液化细胞和贮藏细胞所组成,此外,还有少部分分生细胞。没有发现进一步的分化。其染色体数目,2n=30者占71.7%其余则为非整倍体。     

Heritability and genetic correlation of abdominal versus caudal vertebral number in the medaka (Actinopterygii: Adrianichthyidae): genetic constraints on evolution of axial patterning?

Variation in the number of abdominal vs. caudal vertebrae is an important source of morphological diversification of fish. It is not clear, however, whether abdominal and caudal regions evolve independently. Regressions of offspring on parents demonstrated substantial additive genetic variation within populations, i.e. heritability, in both abdominal and caudal vertebral numbers of the medaka ( Oryzias latipes ). However, the heritability of caudal vertebrae tended to be smaller than that of abdominal vertebrae in some estimations, suggesting that abdominal and caudal regions are controlled by separate developmental modules. Furthermore, genetic correlation between abdominal and caudal vertebral numbers, estimated using full-sib family means, was negative but weak, supporting independent evolution. In addition, substantial genetic differentiation among populations was demonstrated in abdominal vertebral numbers, but not in caudal numbers. These results support our view that Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, in this fish reflects local adaptations of abdominal vertebral numbers. In contrast, the low heritability of caudal vertebrae may reflect the intrinsic invariability of genes associated with a change in caudal vertebral numbers. This genetic constraint may have restricted morphological diversification of not only the medaka, but also the Order Beloniformes as a whole.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 867–874.     

Revision of the Euthalia phemius complex (Lepidoptera: Nymphalidae) based on morphology and molecular analyses

Adults of the Euthalia phemius complex, which is composed of three South‐East Asian nymphalid species, Euthalia phemius, Euthalia ipona, and Euthalia euphemia, were genetically analysed by examining mitochondrial and nuclear genes. The E. phemius complex was also examined morphologically, with particular emphasis on wing markings and male genitalia. No significant differences amongst the three species in the complex were detected with respect to either genetic distance or genital morphology. We therefore conclude that the three currently recognized Euthalia species belong to a single species. Accordingly, E. ipona is synonymized with E. phemius. Euthalia euphemia is treated as a subspecies of E. phemius. Type specimens of all taxa and a synonymic list for the E. phemius complex are also given. In addition, we briefly discuss the evolution and biogeography of the species complex. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 304–327.     

Distinct geographical structure across species units evidenced by chloroplast DNA haplotypes and nuclear ribosomal ITS genotypes of Corylopsis (Hamamelidaceae) in the Japanese islands

The geographical distribution of chloroplast DNA (cpDNA) haplotypes and nuclear ribosomal internal transcribed spacer (nrITS) genotypes of Japanese Corylopsis (Hamamelidaceae), which consists of four species, was investigated. Two hundred and five individuals belonging to four species from 30 populations, covering the entire geographical range, were studied. Based on approximately 1108 bp of the three non-coding regions of cpDNA, nine haplotypes were detected, and each was distinguished from adjacent haplotypes by one substitution. Based on approximately 507-bp nrITS sequences, 47 genotypes were detected, for which three clades were identified in the phylogenetic analysis. There was inconsistency between the cpDNA haplotypes, nrITS genotypes, and classification of Corylopsis taxa, possibly because of incomplete lineage sorting or introgressive hybridization. The distribution of the haplotypes was highly structured geographically, and N _ST (0.893) was significantly greater than G _ST (0.819), implying that the current distribution of Corylopsis species was structured phylogeographically during Quaternary climatic oscillations. The haplotype composition and results of analysis of molecular variance showed that the populations in Hokuriku were highly divergent, suggesting that they are long-term persistent populations arising from refugia during the Quaternary climatic oscillations. Refugial populations in Chugoku and Shikoku may have lost genetic diversity because of a bottleneck resulting from a small population size, followed by post-glacial range expansion. Pre-existing refugia may have been so small that the subsequent range expansion replaced the pre-existing genetic structure.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 501–518.     

Effect of metanotal secretion ingestion on oviposition in a tree cricket, Truljalia hibinonis (Orthoptera: Gryllidae)

The female Truljalia hibinonis ingests metanotal secretions of the male during copulation. The effect of ingestion on oviposition behavior was compared between three female groups: females that copulated once with an intact male (a male that had not been manipulated; M group); females that copulated once with a male from which most of the metanotal secretion had been removed (NO group); and females that copulated once with an intact male followed by being artificially supplied with metanotal secretion three times (MS group). There were no obvious differences in female fecundity across the three groups. However, within the MS group, intake of an optimal amount of metanotal secretion increased the number of eggs laid. This effect appeared quickly after ingestion and was most effective on the first bout (eggs laid during the first few days after copulation) after ingestion of the metanotal secretion. In contrast, the number of eggs laid had a negative correlation with the amount of metanotal secretion ingested when the amount exceeded the optimal in this experimental arrangement.