Biomedical subjects

Dennis E Mathews

Publications and source records attributed to Dennis E Mathews.

3 recordsLinked to original sources

PubMed2005

Multiple type-B response regulators mediate cytokinin signal transduction in Arabidopsis.

Type-B Arabidopsis thaliana response regulators (ARRs) are transcription factors that function in the final step of two-component signaling systems. To characterize their role in plant growth and development, we isolated T-DNA insertions within six of the genes (ARR1, ARR2, ARR10, ARR11, ARR12, and ARR18) from the largest subfamily of type-B ARRs and also constructed various double and triple combinations of these mutations. Higher order mutants revealed progressively decreased sensitivity to cytokinin, including effects on root elongation, lateral root formation, callus induction and greening, and induction of cytokinin primary response genes. The triple mutant arr1,10,12 showed almost complete insensitivity to cytokinin under many of the assay conditions used. By contrast, no significant change in the sensitivity to ethylene was found among the mutants examined. These results indicate that there is functional overlap among the type-B ARRs and that they act as positive regulators of cytokinin signal transduction.

Arabidopsis↗

PubMed2004

Type-B response regulators display overlapping expression patterns in Arabidopsis.

Two-component signaling systems, involving His kinases, His-containing phosphotransfer proteins, and response regulators, have been implicated in plant responses to hormones and environmental factors. Genomic analysis of Arabidopsis supports the existence of 22 response regulators (ARRs) that can be divided into at least two distinct groups designated type-A and type-B. Phylogenetic analysis indicates that the type-B family is composed of one major and two minor subfamilies. The expression of the type-B ARRs was examined by using both reverse transcription-PCR and beta-glucuronidase fusion constructs. The major subfamily of type-B ARRs showed particularly high expression in regions where cytokinins play a significant role, including cells in the apical meristem region and in young leaves that would be undergoing cell division. Multiple members within this same subfamily of type-B ARRs were expressed near the root tip with highest expression in the root elongation zone. beta-Glucuronidase-fusions to full-length ARR2, ARR12, and ARR19 were nuclear localized, consistent with a role in transcriptional regulation. These data suggest that differing expression levels of the type-B ARRs may play a role in modulating the cellular responses to cytokinin.

Arabidopsis↗

PubMed2002

Effect of ethylene pathway mutations upon expression of the ethylene receptor ETR1 from Arabidopsis.

The ethylene receptor family of Arabidopsis consists of five members, one of these being ETR1. The effect of ethylene pathway mutations upon expression of ETR1 was examined. For this purpose, ETR1 levels were quantified in mutant backgrounds containing receptor loss-of-function mutations, ethylene-insensitive mutations, and constitutive ethylene response mutations. Ethylene-insensitive mutations of ETR1 resulted in a posttranscriptional increase in levels of the mutant receptor. Treatment of seedlings with silver, which leads to ethylene insensitivity, also resulted in an increase in levels of ETR1. Loss-of-function mutations of ETR1 resulted in both transcriptional and posttranscriptional changes in levels of the receptor. Most other ethylene pathway mutations, including a newly isolated T-DNA insertion mutation in the gene encoding the ethylene receptor ERS1, had relatively minor effects upon the expression of ETR1. Our results indicate that mutations in ETR1 can affect expression at the posttranscriptional level, and suggest that these posttranscriptional changes may contribute to the phenotypes observed in the mutants. Our results also refine the model on how mutations in ethylene receptors are able to confer dominant ethylene insensitivity upon plants.

Arabidopsis↗