Genetic basis of the multi-left-marginal mutant

Systematic Redefinition of the Hypotricha (Alveolata, Ciliophora) Based on Combined Analyses of Morphological and Molecular Characters

The systematics of Hypotricha is one of the most puzzling problems in ciliate biology, having spanned numerous conflicting hypotheses with unstable relationships at various levels in molecular trees, for which the constant addition of newly discovered species has only increased the confusion. The hypotrichs comprise a remarkable morphologically diversified group of ciliates, and the phylogenetic potential of morphological traits is generally recognized. However, such characters were rarely used in phylogenetic reconstructions, and congruence with molecular data never assessed from simultaneous analyses. To properly reconciliate morphological and molecular information, maximum-likelihood and parsimony analyses of 79 morphological characters and 18S rDNA sequences were performed for 130 ingroup terminals, broadly sampled to represent the known hypotrich diversity. As result, well-supported and relatively stable clades were recovered, based on which the redefined Hypotricha comprises at least six higher taxa: The "arcuseriids", Holostichida, Parabirojimida, and the "amphisiellids", plus the two large clades Kentrurostylida nov. tax. (Hispidotergida nov. tax. and Simplicitergida nov. tax.) and Diatirostomata nov. tax. ("bistichellids", "kahliellids", Gonostomatida and Dorsomarginalia [Postoralida nov. tax. and Uroleptida]). Each taxon was circumscribed by synapomorphies, of which most were homoplastic, as the natural history of hypotrichs is portrayed by an outstanding quantity of convergences and reversions.

Selfish genetic elements and their role in evolution: the evolution of sex and some of what that entails

An individual is often considered (sometimes implicitly) to be the product of a well functioning mutualism between its constituent genes. This however need not be so. One consequence of sexual reproduction is that costly competition within an individual between genes that are effectively allelic can provide the conditions for the spread of suppressors of such competition. The spread of both these ultracompetitive alleles (alias selfish genetic elements) and their suppressors is evidence of a 'conflict of interests' within the genome. That this conflict is a potentially important force in the evolution of genetic systems is illustrated by consideration of the problem of the evolution of sexes (alias mating types). One hypothesis holds that sexes are the result of selection on nuclear genes to coordinate the inheritance of cytoplasmic genomes (usually this means the enforcement of uniparental inheritance) so as to prevent competition between unrelated cytoplasmic genomes. This hypothesis is tested against five comparative predictions and shown to receive considerable empirical support.

Interactions between janus and bcd cortical pattern mutants in Tetrahymena thermophila : An investigation of intracellular patterning mechanisms using double-mutant analysis

An analysis of bcd, janA; bcd, janB; and bcd, janC double-mutant phenotypes in Tetrahymena thermophila has allowed us to examine patterning processes affected by two different classes of mutations. bcd brings about a broadening of the oral and contractile vacuole pore domains in the ciliate cortex, while the janus mutations generate a mirror-image duplication of the ventral cortical pattern. We observed both bcd and janus characteristics expressed in the double mutants, as well as features unique to the double-mutant. Temperature-shift experiments employing the temperature-sensitive janB mutation in a double-mutant (bcd, janB) combination allowed us to observe the changes in pattern as a mirror-image geometry was brought into expression and subsequently removed within the bcd, janB double homozygote. These experiments suggest that there are multiple pattern-mechanisms at work with differing kinetics of expression in the ciliate cortex. We discuss how the bcd mutation could influance expression of the janus mutations in light of a model previously proposed to account for the janus phenotype.