Vegetative propagation strategies of four rupestrian species of Leiothrix (Eriocaulaceae)

Leiothrix is endemic of South America and includes 37 species, 25 of which occur in the state of Minas Gerais. Nineteen of those occur in the "Serra do Cipó", a mountain chain, located in the southern portion of the Espinhaço mountain range. This study examines vegetative propagation strategies of four species of Leiothrix, endemic to the Minas Gerais portion of the Espinhaço mountain range. For each species we established permanent plots, where we marked 30 to 51 rosettes or clones, and then took morphological and phenological measurements. Leiothrix crassifolia (Bong.) Ruhland and L. curvifolia var. lanuginosa (Bong.) Ruhland are rhizomatous, forming compact clones. Leiothrix vivipara (Bong.) Ruhland does not produce rhizomes, but is pseudoviviparous, i.e., produces numerous ramets originating from inflorescences. These ramets are formed precociously, and the flower heads do not touch the ground. In Leiothrix spiralis (Bong.) Ruhland both of these strategies are seen: it is both rhizomatous and pseudoviviparous. In this species, the ramets are formed late, only after the flower head has touched the ground. One of the typical conditions of the rupestrian grasslands is soil water shortage in some periods of the year and nutrient scarcity all year round. These conditions might have created an ideal ecological scenario for the evolution of both pseudovivipary and rhizomatous clonal growth in Leiothrix.

Inducing mutations in the mouse genome with the chemical mutagen ethylnitrosourea

When compared to other model organisms whose genome is sequenced, the number of mutations identified in the mouse appears extremely reduced and this situation seriously hampers our understanding of mammalian gene function(s). Another important consequence of this shortage is that a majority of human genetic diseases still await an animal model. To improve the situation, two strategies are currently used: the first makes use of embryonic stem cells, in which one can induce knockout mutations almost at will; the second consists of a genome-wide random chemical mutagenesis, followed by screening for mutant phenotypes and subsequent identification of the genetic alteration(s). Several projects are now in progress making use of one or the other of these strategies. Here, we report an original effort where we mutagenized BALB/c males, with the mutagen ethylnitrosourea. Offspring of these males were screened for dominant mutations and a three-generation breeding protocol was set to recover recessive mutations. Eleven mutations were identified (one dominant and ten recessives). Three of these mutations are new alleles (Otop1mlh, Foxn1sepe and probably rodador) at loci where mutations have already been reported, while 4 are new and original alleles (carc, eqlb, frqz, and Sacc). This result indicates that the mouse genome, as expected, is far from being saturated with mutations. More mutations would certainly be discovered using more sophisticated phenotyping protocols. Seven of the 11 new mutant alleles induced in our experiment have been localized on the genetic map as a first step towards positional cloning.