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Sex determination in plants leads to the development of unisexual flowers from an originally bisexual floral meristem (1,2). This mechanism results in the enhancement of outcrossing and promotes genetic variability, [...]

Introduction In higher plants, most species show cosexual expression in which male and female organs occur in the same individual (Yampolsky and Yampolsky 1922; Renner and Ricklefs 1995). However, many [...], Two sex-linked fragments were identified by RAPD analyses in the dioecious diploid shrub Aucuba japonica var. ovoidea and were converted into markers of male-specific sequence characterized amplified region (SCAR) markers. PCRs using the primers designed in this study correctly discriminated 24 flowering males and 24 flowering females at higher annealing temperatures (SCAR markers OPA10-424 at 55°C and OPN11-1095 at 65°C), although at relatively low annealing temperatures, the fragments were amplified in both males and females. These SCAR primers were also tested to see whether they were applicable to sex identification in the conspecific tetraploid Aucuba japonica var. japonica. One set pf SCAR primers could be used for sex identification even in this tetraploid variety, although the other failed. The SCAR markers developed in this study will provide a powerful tool in identifying the sex of immature plants of dioecious A. japonica, which is a commercially valuable shrub due to its conspicuous fruits. Key words: Aucuba japonica, dioecy, SCAR, sex determination, shrub. Deux amplicons lies au sexe et identifies par analyse RAPD chez l'arbuste dioique diploide Aucuba japonica var. ovoidea ont ete convertis en marqueurs SCAR (<< sequence characterized amplified region >>) specifiques du sexe male. Des amplifications PCR a l'aide de ces amorces ont permis d'identifier correctement 24 plants males en fleurs et 24 plants femelles en fleurs a des temperatures d'appariement plus elevees (55°C pour le marqueur OPA10-424 et 65°C pour le marqueur OPNl1-1095) tandis que ces fragments etaient tous deux amplifies indifferemment chez les males et les femelles a des temperatures d'appariement plus basses. Ces amorces SCAR ont egalement ete mises a l'essai chez le tetraploide apparente Aucuba japonica var. japonica pour voir si elles permettaient de distinguer les sexes. Une des paires d'amorces SCAR a permis d'effectuer le sexage chez la variete tetraploide tandis que l'autre s'en est montree incapable. Les marqueurs SCAR developpes au cours de ce travail fournissent un outil puissant pour le sexage de plantes immatures de l'A. japonica dioique, laquelle est une espece de grande valeur commerciale en raison de ses fruits voyants. Mots-cles : Aucuba japonica, diecie, SCAR, determination du sexe, arbuste. [Traduit par la Redaction]

Sex determination in honeybees (Apis mellifera) is governed by heterozygosity at a single locus harbouring the complementary sex determiner (csd) gene (1), in contrast to the well-studied sex chromosome system [...]

I. Introduction II. The Chromosomal Basis of Mammalian Sex Determination III. Morphology and Cell Biology of the Developing Gonad A. The bipotential gonad B. Development and differentiation of the ductal [...]

The Sex-lethal (SXL) protein belongs to the family of RNA-binding proteins and is involved in the regulation of pre-mRNA splicing. SXL has undergone an obvious change of function during the [...]

We cloned Bm-Sxl, an orthologue of the Drosophila melanogaster Sex-lethal (Sxl) gene from embryos of Bombyx mori. The full-length cDNAs were of 2 sizes, 1528 and 1339 bp, and were [...]

The evolution of sex continues to be a major problem in biology. Despite the prevalence of sex in the vast majority of higher organisms, it remains questionable whether the benefits [...]

In many animal species, sex- and species-specific bouquets of odors elicit subtle changes in potential sexual partners, which in turn may respond by appropriate behavior (1). In the fruit fly [...], Pheromones are intraspecific chemical signals important for mate attraction and discrimination. In the fruit fly Drosophila melanogaster, hydrocarbons on the cuticular surface of the animal are sexually dimorphic in both their occurrence and their effects: Female-specific molecules stimulate male sexual excitation, whereas the predominant male-specific molecule tends to inhibit male excitation. Complete feminization of the pheromone mixture produced by males was induced by targeted expression of the transformer gene in adult oenocytes (subcuticular abdominal cells) or by ubiquitous expression during early imaginal life. The resulting flies generally exhibited male heterosexual orientation but elicited homosexual courtship from other males.

Dosage compensation is an essential chromosome-wide regulatory process that modulates the expression of numerous genes related solely by their linkage to the same chromosome. The need for dosage compensation arises [...], In nematodes, flies, and mammals, dosage compensation equalizes X-chromosome gene expression between the sexes through chromosome-wide regulatory mechanisms that function in one sex to adjust the levels of X-linked transcripts. Here, a dosage compensation complex was identified in the nematode Caenorhabditis elegans that reduces transcript levels from the two X chromosomes in hermaphrodites. This complex contains at least four proteins, including products of the dosage compensation genes dpy-26 and dpy-27. Specific localization of the complex to the hermaphrodite X chromosomes is conferred by XX-specific regulatory genes that coordinately control both sex determination and dosage compensation.

Sex determination is a particularly appealing model system in which to study developmental biology because the developmental decision is made between only two alternative states, male or female, each of [...], In both Drosophila melanogaster and Caenorhabditis elegans somatic sex determination, germline sex determination, and dosage compensation are controlled by means of a chromosomal signal known as the X:A ratio. A variety of mechanisms are used for establishing and implementing the chromosomal signal, and these do not appear to be similar in the two species. Instead, the study of sex determination and dosage compensation is providing more general lessons about different types of signaling pathways used to control alternative developmental states of cells and organisms.

Field measurements of natural selection have become increasingly popular (Grant 1985; Campbell 1989; Galen 1989; Rausher and Simms 1989; Scheiner 1989; Schemske and Horvitz 1989; Simms 1990; Weis et al. [...]

INTRODUCTION Segregation of the germline from the soma marks the most basic dichotomous decision in development. As illustrated below in the examples of Volvox, Drosophila, and mouse, different organisms specify [...]

SOMATIC SEXUAL DIFFERENTIATION IN Drosophila melanogaster is accomplished by a hierarchy of regulatory genes that act in response to the number of X chromosomes relative to the number of sets [...]

Certain isofemale lines of Drosophila only give rise to daughters following the death of male embryos (1). Male death is due to the presence of intracellular bacteria that pass from [...], Bacteria that selectively kilt males ('male-killers') were first characterized more than 50 years ago in Drosophila and have proved to be common in insects. However, the mechanism by which sex specificity of virulence is achieved has remained unknown. We tested the ability of Spiroplasma poulsonii to kilt Drosophila melanogaster mates carrying mutations in genes that encode the dosage compensation complex. The bacterium failed to kilt mates tacking any of the five protein components of the complex.

EXAMINATION OF AROMATASE AND STEROIDOGENIC FACTOR-1 EXPRESSION DURING TSD IN A REPTILE. Chris Murdock and Thane Wibbels, Dept. of Biology, Univ. of Ala.-Birmingham, Birmingham, AL 35294. Steroids, in particular estrogens, [...]

Sex in birds, as well as in humans and other mammals, is determined by genes on specialized sex chromosomes. Mammalian females have two X chromosomes and males a single X [...]

There are obvious physical differences between males and females, such as the antlers of a male deer and the elaborate tail of a male peacock. Despite pronounced phenotypic differences between [...]