Biomedical subjects

Jan Bart Rossel

Publications and source records attributed to Jan Bart Rossel.

3 recordsLinked to original sources

PubMed2006

A mutation affecting ASCORBATE PEROXIDASE 2 gene expression reveals a link between responses to high light and drought tolerance.

Molecular analyses of plants have revealed a number of genes whose expression changes in response to high light (HL), including the H2O2 scavenger, ASCORBATE PEROXIDASE 2 (APX2). We carried out a screen in Arabidopsis thaliana for lesions that alter HL-induced expression of APX2 to identify components in abiotic stress signalling pathways. High light was used as it can be instantaneously applied or removed and accurately measured. We identified a number of alx mutations causing altered APX2 expression. Here we describe the gain-of-function mutant, alx8, which has constitutively higher APX2 expression and higher levels of foliar abscisic acid (ABA) than wild type. In fact, exogenous ABA increased APX2 expression and the APX2 promoter contains ABA response elements. Furthermore, we have shown that HL stress increases ABA in wild-type plants, implicating ABA in the regulation of HL-inducible genes. The alx8 mutant is drought tolerant, exhibits improved water-use efficiency and a number of drought-tolerance genes are upregulated. Additionally, alx8 demonstrates the complexity of ABA-dependent and ABA-independent transcriptional networks as some components in both pathways are upregulated in alx8. This study provides evidence for common steps in drought and HL stress response pathways.

Abscisic Acid↗

PubMed2004

Identifying photoprotection mutants in Arabidopsis thaliana.

Plants have a range of mechanisms to protect against oxidative damage induced by excess light and environmental stress. One of these processes consists of the detoxification of reactive oxygen species by the ascorbate peroxidase (APX) family of enzymes, which convert H2O2 into H2O. Two of the genes encoding APX in Arabidopsis are induced by high light, namely APX1 and APX2. We have applied a genetic approach to understanding the mechanisms of photoprotection, using APX2 as an indicator of oxidative stress. Transgenic plants containing the reporter gene luciferase linked to the APX2 promoter were EMS mutagenized and kindly provided to us by Mullineaux and colleagues. We have screened this mutagenized seed to identify mutants with aberrant photoprotection, based on altered luminescence resulting from altered luciferase activity. Here we describe the screen and steps involved in the identification of the mutations in an effort to identify novel photoprotective genes and products.

Arabidopsis↗

PubMed2002

Global changes in gene expression in response to high light in Arabidopsis.

A range of environmental conditions can lead to oxidative stress; thus, a prompt and effective response to oxidative stress is crucial for the survival of plants. Microarray and northern-blot analyses were performed toward the identification of the factors and signaling pathways that enable plants to limit oxidative damage caused by exposure to high light (HL). Arabidopsis plants grown under moderate light (100 micromol m(-2) s(-1)) were exposed to HL (1,000 micromol m(-2) s(-1)) for 1 h. The microarray analyses revealed that exposure of Arabidopsis to HL caused an increase in known antioxidant genes, as well as several unknown genes. Some of these unknown genes had homologies to possible regulatory genes and metabolic enzymes. Furthermore, it was found that a range of chaperones were up-regulated in the HL treatment and that this induction was specifically due to the HL stress. The temporal expression under HL and different oxidative stress conditions of a subset of HL-responsive genes was confirmed via northern-blot analysis. Results from the arrays were also compared with publicly available microarray data sets from a range of different stress conditions at the Arabidopsis Functional Genomics Consortium. This cross comparison enabled the identification of genes that may be induced by changes in redox poise. Finally, to determine if the genes that were differentially expressed by HL stress were under similar transcriptional control, we analyzed the promoter sequences for the presence of common motifs.

Antioxidants↗