A mutation in the purine biosynthetic enzyme ATASE2 impacts high light signalling and acclimation responses in green and chlorotic sectors of Arabidopsis leaves.

In this report, we investigate the altered APX2 expression 13 (alx13) mutation of Arabidopsis thaliana, a mutation in glutamine phosphoribosyl pyrophosphate amidotransferase 2 (ATASE2), the primary isoform of the enzyme mediating the first committed step of purine biosynthesis. Light-dependent leaf variegation was exhibited by alx13 plants, with partial shading of alx13 rosettes revealing that the development of chlorosis in emerging leaves is influenced by the growth irradiance of established leaves. Chlorotic sectors arose from emerging green alx13 leaves during a phase of rapid cell division and expansion, which shows that each new cell's fate is independent of its progenitor.

Systemic and intracellular responses to photooxidative stress in Arabidopsis.

As the sun tracks daily through the sky from east to west, different parts of the canopy are exposed to high light (HL). The extent of and mechanisms by which a systemic acquired acclimation (SAA) response might preacclimate shaded leaves that will be subsequently exposed to full sunlight is largely undefined. We investigated the role of an Arabidopsis thaliana zinc finger transcription factor, ZAT10, in SAA.

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.

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.

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.