Investigating the role of plant heat shock proteins during oxidative stress

Abstract

Oxidative stress, arising from an imbalance in the generation and removal of reactive oxygen species (ROS), is a challenge faced by all aerobic organisms. In plants, different pathways sense ROS from extracellular sources or organelles such as mitochondria, chloroplast or peroxisome. In our recent paper in Plant Molecular Biology¹ we have studied the Arabidopsis thaliana early response to the generation of superoxide anion in chloroplasts during active photosynthesis. Transcript profile analysis revealed that the expression level of various genes encoding heat shock proteins (Hsps), increased after a short term of oxidative stress treatment. Furthermore, there was an induction of heat shock transcription factors HsfA2 and HsfA4A that were reported to be regulators of genes involved in stress response of Arabidopsis.^1,2

In this addendum, we complement the expression analysis of two Hsp genes encoding Hsp70 and a 17.6 kDa class I small heat-shock protein (sHsp), and discuss their plausible role during oxidative stress, considering our data and other recently published papers.

Addendum to: Scarpeci TE, Zanor MI, Carrillo N, Mueller-Roeber B, Valle EM. Generation of superoxide anion in chloroplasts of Arabidopsis thaliana during active photosynthesis: a focus on rapidly induced genes. Plant Mol Biol 2008; 66:361-78.

Figures and Tables

Figure 1 Northern blot analysis of the effect of MV concentration on the steady state level of transcripts encoding Hsp70 and sHSP. Two-week-old Arabidopsis plants were exposed to different MV concentrations for 2 h in the light. Twenty micrograms of total RNA from each sample were fractionated on formaldehyde-agarose gels, transferred to nylon membranes and hybridized with ³²P-labelled Hsp70 or sHsp-specific DNA probes. Ethidium bromide stained rRNA was used as loading control.

Figure 2 Effect of several stresses on transcript levels of Hsp70 and sHsp. Two-week-old Arabidopsis plants (control, 120 µmol quanta m⁻² s⁻¹, 16 h light period at 25°C) were exposed to wilting (2 h), heat shock (45°C, 2 h), UV-light (15 and 30 min) and different light intensities (120, 550 and 950 µmol quanta m⁻² s⁻¹ for 2 h). Transcript levels of Hsp70 and sHsp were detected using RNA gel-blot analysis. Each lane was loaded with 20 µg total RNA. Equal loading was verified by rRNA visualization after ethidium bromide staining.

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