Systemic and Intracellular Responses to Photooxidative Stress inArabidopsis

Abstract

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. ZAT10 overexpression resulted in enhanced tolerance to photoinhibitory light and exogenous H 2 O 2 , increased expression of antioxidative genes whose products are targeted to multiple subcellular compartments. Partial HL exposure of a leaf or leaves rapidly induced ZAT10 mRNA in distal, shaded photosynthetic tissues, including the floral stem, cauline leaves, and rosette, but not in roots. Fully 86% of fivefold HL-upregulated and 71% of HL-downregulated genes were induced and repressed, respectively, in distal, shaded leaves. Between 15 and 23% of genes whose expression changed in the HL and/or distal tissues were coexpressed in the ZAT10 overexpression plants, implicating ZAT10 in modulating the expression of SAA-regulated genes. The SAA response was detectable in plants with mutations in abscisic acid, methyl jasmonate, or salicylic acid synthesis or perception, and systemic H 2 O 2 diffusion was not detected. Hence, SAA is distinct from pathogen-stimulated systemic acquired resistance and apparently involves a novel signal or combination of signals that preacclimate photosynthetic tissues to HL.

Unraveling the Tapestry of Networks Involving Reactive Oxygen Species in Plants

“…Transgenics with enhanced or suppressed ZAT10 levels were more tolerant to multiple stresses (Mittler et al, 2006;Rossel et al, 2007). A remarkable tolerance to drought stress has been reported recently in transgenic tobacco plants that express an isopentenyltransferase gene under the control of a drought stress-responsive promoter (Rivero et al, 2007).…”

Oxidative Stress: Antagonistic Signaling for Acclimation or Cell Death?

“…For both systemic acquired acclimation to excess light and systemic acquired resistance to biotrophic pathogens, the underlying responses seem to predominantly involve reiteration of the events in challenged leaves, but with much less intensity (Alvarez et al, 1998;Karpinski et al, 1999;Rossel et al, 2007;Mü hlenbock et al, 2008). The reduced intensity of the response may represent a raised threshold that pushes cells more into acclimation or resistance and away from cell death at an earlier stage.…”

The functions of WHIRLY1 and REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 in cross tolerance responses in plants: a hypothesis

“…R. Soc. B 369: 20130226 [5,7,15,43,44]. Relatively few components that are involved in systemic light signalling pathways have been identified to date.…”

“…Cross-tolerance phenomena are often associated with the accumulation of reactive oxygen species (ROS) and altered redox and phytohormone signalling, particularly through ethylene (ET), salicylic acid (SA), abscisic acid (ABA) and jasmonate (JA)-mediated pathways [11][12][13][14]. Chloroplasts play an important role in redox signalling events linking light acclimation responses to immunity to pathogens as well as in the synthesis of important plant hormones such as ABA, JA and strigolactones [5][6][7][8][9][10][11][15][16][17]. Moreover, chloroplasts play an important role in systemic as well as local signals, facilitating a whole plant response to the high light experienced by a single leaf, a process that is called systemic acquired acclimation or systemic acquired resistance (SAR) [6,7].…”

“…Chloroplast-to-nucleus retrograde signalling is important for acclimation and defence responses [6,7,15,[18][19][20][21][22][23][24][25][26]. Many metabolites such as intermediates of tetrapyrrole biosynthesis such as Mg-ProtoIX, haem, 3 0 -phosphoadenosine 5 0 -phosphate (PAP); b-cyclocitral, ROS and methylerythritol cyclodiphosphate are considered to act as signalling molecules involved in the transmission of signals to the nucleus [18][19][20][21][22][23][24][25][26].…”