The Arabidopsis glutathione transferase gene family displays complex stress regulation and co‐silencing multiple genes results in altered metabolic sensitivity to oxidative stress

Abstract

SummaryPlant glutathione transferases (GSTs) are induced by diverse biotic and abiotic stimuli, and are important for protecting plants against oxidative damage. We have studied the primary transcriptional stress response of the entire Arabidopsis GST family to seven stresses, including both biotic and abiotic stimuli, with a focus on early changes in gene expression. Our results indicate that individual GST genes are highly specific in their induction patterns. Furthermore, we have been able to link individual GSTs to particular stress stimuli. Using RNAi, we successfully co-silenced a group of four phi GSTs that represent some of the most highly expressed GST genes. Despite a marked reduction in total phi GST protein levels, the transgenic plants showed no reduction in GST activity as measured using the model substrate 1-chloro-2,4-dinitrobenzene (CDNB), and appeared to have surprisingly robust physical phenotypes during stress. However, analysis of metabolite pools showed oxidation of the glutathione pool in the RNAi lines, and we observed alterations in carbon and nitrogen compounds following salicylic acid and hydrogen peroxide stress treatments, indicative of oxidative modification of primary metabolism. Thus, there appears to be a high degree of functional redundancy within the Arabidopsis GST family, with extensive disruption being required to reveal the roles of phi GSTs in protection against oxidative stress.

Salicylic Acid-Dependent Plant Stress Signaling via Mitochondrial Succinate Dehydrogenase

“…Their measured signals and SA responses may come from background reactions independent of an active respiratory system inside mitochondria. In plants, GSTs are induced by SA, ROS (H 2 O 2 ), and biotic/abiotic stresses (Moons, 2005), and GSTF8 is a well-described representative marker for early stress/ defense gene induction (Chen et al, 1996;Sappl et al, 2009). In this study, we show that the lack of induction of GSTF8:luc by SA in dsr1 (Gleason et al, 2011) can be mimicked by reduced FAD insertion and assembly of SDH1-1 through knockdown of the SDH assembly factor SDHAF2.…”

Safeners recruit multiple signalling pathways for the orchestrated induction of the cellular xenobiotic detoxification machinery in Arabidopsis

“…The existence of multiple signalling pathways is supported by other gene expression profiling experiments, including a recent study on the stress-induced expression of the GST family in Arabidopsis. Transcripts for seven of the nine GSTUs that were shown here to be induced by safeners in Arabidopsis shoots had also been found to accumulate in Arabidopsis cell cultures after exposure to different stress treatments (Sappl et al 2009). However, each of the applied stresses induced only a subset of the 7 GSTUs (e.g.…”

“…However, each of the applied stresses induced only a subset of the 7 GSTUs (e.g. chilling: GSTU3; hypoxia: GSTU1, 3, 7, 25; chitin: GSTU11; SA: GSTU1, 3, 7;H2O2: GSTU3, 4, 5, 7, 11, 25;Sappl et al 2009), suggesting that multiple stress signalling pathways are activated by safeners simultaneously.…”

Mitochondrial complex II has a key role in mitochondrial-derived reactive oxygen species influence on plant stress gene regulation and defense

“…In plants, the transcriptional activation of diverse GSTs can be triggered by chemicals [salicylic acid (SA)], auxinic herbicides (e.g., dicamba), and ROS (H 2 O 2 ) as well as both biotic (fungal and bacterial elicitors) and abiotic stresses (6). A good example is GSTF8, which has been used as a marker for early stress/defense gene induction (7)(8)(9). Mutants with altered GSTF8 expression could provide critical information about the regulation of gene expression such as novel transcription factors or other upstream regulatory components with roles in plant defense and/or stress responses.…”