Impact of chloroplastic- and extracellular-sourced ROS on high light-responsive gene expression in Arabidopsis

Abstract

The expression of 28 high light (HL)-responsive genes of Arabidopsis was analysed in response to environmental and physiological factors known to influence the expression of the HL-responsive gene, ASCOR-BATE PEROXIDASE2 (APX2). Most (81%) of the HL-responsive genes, including APX2, required photosynthetic electron transport for their expression, and were responsive to abscisic acid (ABA; 68%), strengthening the impression that these two signals are crucial in the expression of HL-responsive genes. Further, from the use of mutants altered in reactive oxygen species (ROS) metabolism, it was shown that 61% of these genes, including APX2, may be responsive to chloroplast-sourced ROS. In contrast, apoplastic/ plasma membrane-sourced H 2 O 2 , in part directed by the respiratory burst NADPH oxidases AtrbohD and AtrbohF, was shown to be important only for APX2 expression. APX2 expression in leaves is limited to bundle sheath parenchyma; however, for the other genes in this study, information on their tissue specificity of expression is sparse. An analysis of expression in petioles, enriched for bundle sheath tissue compared with distal leaf blade, in HL and control leaves showed that 25% of them had >10-fold higher expression in the petiole than in the leaf blade.However, this did not mean that these petiole expression genes followed a pattern of regulation observed for APX2.

Oxidative Stress: Antagonistic Signaling for Acclimation or Cell Death?

“…We suggest that this non-ROS signal is destined to activate AtrbohD and AtrbohF NADPH oxidases at the plasma membrane. The involvement of AtrbohD/F and a strong rapid accumulation of extracellular H 2 O 2 in high-light signaling has been observed (Davletova et al, 2005;Bechtold et al, 2008;Galvez-Valdivieso et al, 2009;Miller et al, 2009). As with the involvement of AtrbohD and AtrbohF in ABA signaling in guard cells (Kwak et al, 2003;Miao et al, 2006), we suggest that H 2 O 2 produced at the plasma membrane could oxidize glutathione peroxidase isoforms, which in turn would bind to and inhibit ABI1 and ABI2 in BSCs.…”

The Paralogous GenesRADICAL-INDUCED CELL DEATH1andSIMILAR TO RCD ONE1Have Partially Redundant Functions during Arabidopsis Development

“…SRO1 expression level varies less in response to abiotic stress than RCD1, but neither gene shows large changes in expression in response to any of the abiotic stresses tested by microarray. However, RCD1 transcript has been shown to accumulate under high light stress (Bechtold et al, 2008); SRO1 transcript has not been reported to do so. This suggests that transcription or transcript stability of RCD1 may be regulated during the response to specific abiotic stresses.…”

Fast Retrograde Signaling in Response to High Light Involves Metabolite Export, MITOGEN-ACTIVATED PROTEIN KINASE6, and AP2/ERF Transcription Factors in Arabidopsis

“…When leaves were pretreated with H 2 O 2 prior to the shift to excess excitation conditions, they developed less photooxidative damage and APX2 transcript levels, a stress marker, accumulated to lower levels (Karpinski et al, 1999). Based on these findings, H 2 O 2 was suggested to function as messenger in local and systemic signaling in response to excess light (Bechtold et al, 2008). In line with these results, H 2 O 2 transiently accumulated at t = 30 min in the L→H experiment (Figure 3), supporting its suggested role in signal transmission.…”