Mutant

About: Mutant is a research topic. Over the lifetime, 74520 publications have been published within this topic receiving 3477079 citations.

Root development in Arabidopsis: four mutants with dramatically altered root morphogenesis

Abstract: A genetic analysis of root development in Arabidopsis thaliana has identified mutants that have abnormal morphogenesis. Four of these root morphogenesis mutants show dramatic alterations in post-embryonic root development. The short-root mutation results in a change from indeterminate to determinate root growth and the loss of internal root cell layers. The cobra and lion's tail mutations cause abnormal root cell expansion which is conditional upon the rate of root growth. Expansion is greatest in the epidermal cells in cobra and in the stele cells in lion's tail. The sabre mutation causes abnormal cell expansion that is greatest in the root cortex cell layer and is independent of the root growth rate. The tissue-specific effects of these mutations were characterized with monoclonal antibodies and a transgenic marker line. Genetic combinations of the four mutants have provided insight into the regulation of growth and cell shape during Arabidopsis root development.

Molecular cloning and functional expression of gibberellin 2- oxidases, multifunctional enzymes involved in gibberellin deactivation.

Abstract: A major catabolic pathway for the gibberellins (GAs) is initiated by 2β-hydroxylation, a reaction catalyzed by 2-oxoglutarate-dependent dioxygenases. To isolate a GA 2β-hydroxylase cDNA clone we used functional screening of a cDNA library from developing cotyledons of runner bean (Phaseolus coccineus L.) with a highly sensitive tritium-release assay for enzyme activity. The encoded protein, obtained by heterologous expression in Escherichia coli, converted GA9 to GA51 (2β-hydroxyGA9) and GA51-catabolite, the latter produced from GA51 by further oxidation at C-2. The enzyme thus is multifunctional and is best described as a GA 2-oxidase. The recombinant enzyme also 2β-hydroxylated other C19-GAs, although only GA9 and GA4 were converted to the corresponding catabolites. Three related cDNAs, corresponding to gene sequences present in Arabidopsis thaliana databases, also encoded functional GA 2-oxidases. Transcripts for two of the Arabidopsis genes were abundant in upper stems, flowers, and siliques, but the third transcript was not detected by Northern analysis. Transcript abundance for the two most highly expressed genes was lower in apices of the GA-deficient ga1–2 mutant of Arabidopsis than in wild-type plants and increased after treatment of the mutant with GA3. This up-regulation of GA 2-oxidase gene expression by GA contrasts GA-induced down-regulation of genes encoding the biosynthetic enzymes GA 20-oxidase and GA 3β-hydroxylase. These mechanisms would serve to maintain the concentrations of biologically active GAs in plant tissues.

Domains of the human androgen receptor involved in steroid binding, transcriptional activation, and subcellular localization.

Abstract: A series of human androgen receptor (AR) deletion mutants was constructed to study the relationship between the structural domains and their different functions in the AR protein. Human AR mutants were expressed in COS-1 and HeLa cells to investigate hormone binding, transcriptional activation, and subcellular localization. The wild-type human AR (AR 1910) was expressed as a 110- to 112-kDa doublet, as revealed on immunoblots. All mutant AR proteins also migrated as doublets, except for one. This AR has a deletion from amino acid residues 51-211 and migrated as a single protein band, possibly due to altered posttranslational modification. The AR steroid-binding domain is encoded by approximately 250 amino acid residues in the Cterminal end. Deletions in this domain as well as truncation of the last 12 C-terminal amino acid residues abolished hormone binding. Cotransfection studies in HeLa cells showed that transcriptional activation of an androgen-regulated reporter gene construct was induced by the wildtype human AR. Mutational analysis revealed two regions in the N-terminal part, encoded by amino acid residues 51-211 and 244-360, to be essential for this transcriptional activation. Deletion of the hormone-binding domain yielded a constitutively active AR protein, indicating that in the absence of hormone this domain displays an inhibitory function. In the presence of its ligand, the wild-type AR was located in the cell nucleus. In the absence of androgens the receptor was mainly nuclear, but cytoplasmic localization was observed as well. In contrast, an AR deletion mutant lacking part of the DNAbinding domain and part of the hinge region was exclusively cytoplasmic in the absence of hormone. This mutant AR lacks a region that is highly conserved among steroid receptors and homologous to the simian virus-40 large T-antigen- and nucleoplas

Molecular Characterization of the Major Wheat Domestication Gene Q

Abstract: The Q gene is largely responsible for the widespread cultivation of wheat because it confers the free-threshing character. It also pleiotropically influences many other domestication-related traits such as glume shape and tenacity, rachis fragility, spike length, plant height, and spike emergence time. We isolated the Q gene and verified its identity by analysis of knockout mutants and transformation. The Q gene has a high degree of similarity to members of the AP2 family of transcription factors. The Q allele is more abundantly transcribed than q, and the two alleles differ for a single amino acid. An isoleucine at position 329 in the Q protein leads to an abundance of homodimer formation in yeast cells, whereas a valine in the q protein appears to limit homodimer formation. Ectopic expression analysis allowed us to observe both silencing and overexpression effects of Q. Rachis fragility, glume shape, and glume tenacity mimicked the q phenotype in transgenic plants exhibiting post-transcriptional silencing of the transgene and the endogenous Q gene. Variation in spike compactness and plant height were associated with the level of transgene transcription due to the dosage effects of Q. The q allele is the more primitive, and the mutation that gave rise to Q occurred only once leading to the world's cultivated wheats.