Genetics of white color and iridophoroma in "Lemon Frost" leopard geckos.

The squamates (lizards and snakes) are close relatives of birds and mammals, with more than 10,000 described species that display extensive variation in a number of important biological traits, including coloration, venom production, and regeneration. Due to a lack of genomic tools, few genetic studies in squamates have been carried out. The leopard gecko, Eublepharis macularius, is a popular companion animal, and displays a variety of coloration patterns. We took advantage of a large breeding colony and used linkage analysis, synteny, and homozygosity mapping to investigate a spontaneous semi-dominant mutation, "Lemon Frost", that produces white coloration and causes skin tumors (iridophoroma). We localized the mutation to a single locus which contains a strong candidate gene, SPINT1, a tumor suppressor implicated in human skin cutaneous melanoma (SKCM) and over-proliferation of epithelial cells in mice and zebrafish. Our work establishes the leopard gecko as a tractable genetic system and suggests that a tumor suppressor in melanocytes in humans can also suppress tumor development in iridophores in lizards.

Contrast in chloride exclusion between two grapevine genotypes and its variation in their hybrid progeny.

Potted grapevines of 140 Ruggeri (Vitis berlandieri × Vitis rupestris), a good Cl(-) excluder, and K 51-40 (Vitis champinii × Vitis riparia 'Gloire'), a poor Cl(-) excluder, and of a family obtained by crossing the two genotypes, were used to examine the inheritance of Cl(-) exclusion. Rooted leaves were then used to further investigate the mechanism for Cl(-) exclusion in 140 Ruggeri. In both a potting mix trial (plants watered with 50 mM Cl(-)) and a solution culture trial (plants grown in 25 mM Cl(-)), the variation in Cl(-) accumulation was continuous, indicating multiple rather than single gene control for Cl(-) exclusion between hybrids within the family. Upper limits of 42% and 35% of the phenotypic variation in Cl(-) concentration could be attributed to heritable sources in the potting mix and solution culture trials, respectively. Chloride transport in roots of rooted leaves of both genotypes appeared to be via the symplastic pathway, since addition of 8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS), an apoplastic tracer, revealed no obvious PTS fluorescence in the laminae of either genotype, despite significant accumulation of Cl(-) in laminae of K 51-40 during the PTS uptake period. There was no significant difference in either unidirectional (36)Cl(-) flux (10 min) or (36)Cl(-) uptake (3 h) into roots of rooted leaves exposed to 5, 10, or 25 mM Cl(-). However, the percentage of (36)Cl(-) transported to the lamina (3 h) was significantly lower in 140 Ruggeri than in K 51-40, supporting reduced Cl(-) loading into xylem and implicating the root stele in the Cl(-) exclusion mechanism.

A molecular phylogeny of the orange subfamily(Rutaceae: Aurantioideae) using nine cpDNA sequences.

The breeding of new, high-quality citrus cultivars depends on dependable information about the relationships of taxa within the tribe Citreae; therefore, it is important to have a well-supported phylogeny of the relationships between species not only to advance breeding strategies, but also to advance conservation strategies for the wild taxa. The recent history of the systematics of Citrus (Rutaceae: Aurantioideae) and its allies, in the context of Rutaceae taxonomy as a whole, is reviewed. The most recent classification is tested using nine cpDNA sequence regions in representatives of all genera of the subfam. Aurantioideae (save Limnocitrus) and numerous species and hybrids referred to Citrus s.l. Aurantioideae are confirmed as monophyletic. Within Aurantioideae, tribe Clauseneae are not monophyletic unless Murraya s.s. and Merrillia are removed to Aurantieae. Within tribe Aurantieae, the three traditionally recognized subtribes are not monophyletic. Triphasiinae is not monophyletic unless Oxanthera is returned to Citrus (Citrinae). Balsamocitrinae is polyphyletic. Feroniella, traditionally considered allied closely to Limonia (=Feronia), is shown to be nested in Citrus. The proposed congenericity of Severinia and Atalantia is confirmed. The most recent circumscription of Citrus is strongly supported by this analysis, with hybrids appearing with their putative maternal parents. The genus was resolved into two clades, one comprising wild species from New Guinea, Australia, and New Caledonia (formerly Clymenia, Eremocitrus, Microcitrus, Oxanthera), but surprisingly also Citrus medica, traditionally believed to be native in India. The second clade is largely from the Asian mainland (including species formerly referred to Fortunella and Poncirus).