RESPONSE OF ARABIDOPSIS MSH6 PROTEIN TO HIGH LIGHT STRESS

SPAMPINATO CLAUDIA; GONZALEZ VALENTINA

Rosario

Simposio; Simposio de Genómica Funcional de Plantas; 2017

High light generates an overflow of electrons from the photosynthetic electron transport system which results in the production of reactive oxygen species (ROS). Imbalance between ROS production and detoxification can cause damage to biomolecules such as lipids, proteins and DNA. Oxidative attack on DNA results in a variety of chemical modifications of base moieties. Among them 8-oxo-7,8-dihydroguanine (8oxoG) is the most frequent oxidation product and seems to play a major role in mutagenesis due to frequent mispairings yielding GC → TA transversions. To minimize the burden of 8-oxoG several DNA repair pathways exist. One of them is the mismatch repair (MMR) system. The first step of the pathway involves recognition of the DNA lesion by MutS proteins (MSH2, MSH6 and MSH7). Experiments in various organisms including bacteria, yeast, mouse and human have reinforced the finding that MMR plays a conserved role in preventing mutations associated with oxidative damage (1). To investigate the effect of high light stress on Arabidopsis thaliana, 14 d-old plants grown under normal conditions (100 µmol quanta m-2 s-1) were subsequently exposed for 6-h to high light intensities (600 µmol quanta m-2 s-1) or maintained under normal conditions. Our results demonstrate that MSH2, MSH6 and MSH7 transcript levels were significantly increased in leaves after the treatment. Similar results were observed in our laboratory when plants were irradiated with UV-B (2,3). To gain further insights in light-responsive elements within MSH6 promoter, in silico analysis were performed. Some elements such as GATA (GATA), sequences over-represented in light-induced promoters (SORLIP; GCCAC) and GT1 consensus (GRWAAW) proposed to confer light-mediated gene regulation were found in MSH6 promoter (Figure 1). Interestingly, a near perfect duplication of the SORLIP5 element (CACTCACTC) was found at −241 bp of MSH6. SORLIP motifs were subjected to site-directed mutagenesis. Wild-type and mutant promoter regions were cloned upstream of the GUS reporter gene to define elements within MSH6 that are essential for high light induction of GUS activity.