Untitled

Abstract

A seedling lethal mutant of Nicotiana plumbaginifolia (sdl-1) was isolated by transposon tagging using a maize Dissociation (Ds) element. The insertion mutation was produced by direct co-transformation of protoplasts with two plasmids: one containing Ds and a second with an Ac transposase gene. sdl-1 seedlings exhibit several phenotypes: swollen organs, short hypocotyls in light and dark conditions, and enlarged and multinucleated cells, that altogether suggest cell growth defects. Mutant cells are able to proliferate under in vitro culture conditions. Genomic DNA sequences bordering the transposon were used to recover cDNA from the normal allele. Complementation of the mutant phenotype with the cDNA confirmed that the transposon had caused the mutation. The Ds element was inserted into the first exon of the open reading frame and the homozygous mutant lacked detectable transcript. Phenocopies of the mutant were obtained by an antisense approach. SDL-1 encodes a novel protein found in several plant genomes but apparently missingfrom animal and fungal genomes; the protein is highly conserved and has a potential plastid targeting motif.

A Retrotransposon-Mediated Gene Duplication Underlies Morphological Variation of Tomato Fruit

“…1A). Four of these genes were IQD12 [which belonged to the IQ67 domain-containing plant proteins (5)], an SDL1-like gene with high similarity to a tobacco and Arabidopsis gene (6,7), and two hypothetical genes HYP1 and HYP2 encoding a protein with weak similarity to CUC1 (8) and a 487-amino acid protein with high similarity to a potato protein of unknown function (AY737314), respectively. The fifth gene was DEFL1, encoding a putative secreted defensin protein (BT012682).…”

“…Both nuclei are transcriptionally active and contain two complete copies of the genome (2-4). The parasite has two developmental stages: a binucleate, flagellated trophozoite that attaches to the upper small intestine, and the quadrinucleate infectious cyst, which is excreted from the body and persists in the water supply (7). In the encysting trophozoite, the two nuclei are thought to undergo a nuclear division without a subsequent cytokinesis, giving rise to a mature cyst with four nuclei (8).…”