Heat stress-induced H2O2 is required for effective expression of heat shock genes in Arabidopsis

Abstract

The mechanisms of sensing and signalling of heat and oxidative stresses are not well understood. The central question of this paper is whether in plant cells oxidative stress, in particular H(2)O(2), is required for heat stress- and heat shock factor (HSF)-dependent expression of genes. Heat stress increases intracellular accumulation of H(2)O(2) in Arabidopsis cell culture. The accumulation was greatly diminished using ascorbate as a scavenger or respectively diphenyleneiodonium chloride (DPI) as an inhibitor of reactive oxygen species production. The mRNA of heat shock protein (HSP) genes, exemplified by Hsp17.6, Hsp18.2, and the two cytosolic ascorbate peroxidase genes Apx1, Apx2, reached similar levels by moderate heat stress (37 degrees C) or by treatment with H(2)O(2), butylperoxide and diamide at room temperature. The heat-induced expression levels were significantly reduced in the presence of ascorbate or DPI indicating that H(2)O(2) is an essential component in the heat stress signalling pathway. Rapid (15 min) formation of heat shock promoter element (HSE) protein-binding complex of high molecular weight in extracts of heat-stressed or H(2)O(2)-treated cells and the inability to form this complex after ascorbate treatment suggests that oxidative stress affects gene expression via HSF activation and conversely, that H(2)O(2) is involved in HSF activation during the early phase of heat stress. The heat stress induction of a high mobility HSE-binding complex, characteristic for later phase of heat shock response, was blocked by ascorbate and DPI. H(2)O(2 )was unable to induce this complex suggesting that H(2)O(2) is involved only in the early stages of HSF activation. Significant induction of the genes tested after diamid treatment and moderate expression of the sHSP genes in the presence of 50 mM ascorbate at 37 degrees C occurred without activation of HSF, indicating that other mechanisms may be involved in stress signalling.

Subset of heat-shock transcription factors required for the early response of Arabidopsis to excess light

“…A good candidate for this molecule is H 2 O 2 , which is generated during both heat and EL stress conditions (8,37) (Fig. S1 C and E).…”

The Heat Shock Factor A4A Confers Salt Tolerance and Is Regulated by Oxidative Stress and the Mitogen-Activated Protein Kinases MPK3 and MPK6

“…These results suggest that HSFA4A can act in common pathways with these transcription factors. The expression of several APX and HSP genes is known to be controlled by HSF complexes in response to H 2 O 2 -derived signals during heat stress (Volkov et al, 2006). Similarly, HSFA4A seems to modulate transcription of a set of target genes involved in mounting defense to abiotic and biotic stress stimuli.…”

“…ROS accumulate in response to biotic and abiotic stress and represent important signaling molecules in the coordination of stress acclimation pathways (Foyer and Noctor, 2005;Miller et al, 2010;Suzuki et al, 2012). Generation of ROS signals, in particular hydrogen peroxide (H 2 O 2 ), during heat and oxidative stress mediates the activation of various HSFs and induction of their downstream target genes (Miller and Mittler, 2006;Volkov et al, 2006;Kotak et al, 2007). Specific HSFs are involved in signaling cross talk with key components of ROS signaling, including the mitogen-activated protein (MAP) kinases MPK3 and MPK6 and members of the zincfinger transcription factor families, and thus also contribute to transcriptional control of a large battery of oxidative stress-responsive genes (Davletova et al, 2005b;Miller and Mittler, 2006;Pucciariello et al, 2012;Evrard et al, 2013).…”

Arabidopsis NAC transcription factor JUNGBRUNNEN1 affects thermomemory-associated genes and enhances heat stress tolerance in primed and unprimed conditions

“…Recently, HSFA2 has been shown to play a critical role in thermomemory in Arabidopsis; 9 its expression is rapidly and strongly enhanced by H 2 O 2 treatment. 5 In addition, heat shock-induced H 2 O 2 accumulation has been reported to be required for effective expression of heat shock genes in Arabidopsis, 11 suggesting…”