The zinc-finger protein Zat12 plays a central role in reactive oxygen and abiotic stress signaling in Arabidopsis

Abstract

Plant acclimation to environmental stress is controlled by a complex network of regulatory genes that compose distinct stress-response regulons. In contrast to many signaling and regulatory genes that are stress specific, the zinc-finger protein Zat12 responds to a large number of biotic and abiotic stresses. Zat12 is thought to be involved in cold and oxidative stress signaling in Arabidopsis (Arabidopsis thaliana); however, its mode of action and regulation are largely unknown. Using a fusion between the Zat12 promoter and the reporter gene luciferase, we demonstrate that Zat12 expression is activated at the transcriptional level during different abiotic stresses and in response to a wound-induced systemic signal. Using Zat12 gain- and loss-of-function lines, we assign a function for Zat12 during oxidative, osmotic, salinity, high light, and heat stresses. Transcriptional profiling of Zat12-overexpressing plants and wild-type plants subjected to H(2)O(2) stress revealed that constitutive expression of Zat12 in Arabidopsis results in the enhanced expression of oxidative- and light stress-response transcripts. Under specific growth conditions, Zat12 may therefore regulate a collection of transcripts involved in the response of Arabidopsis to high light and oxidative stress. Our results suggest that Zat12 plays a central role in reactive oxygen and abiotic stress signaling in Arabidopsis.

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Figure 1.

Promoter∷reporter analysis of Zat12 expression in Arabidopsis. A, Luciferase imaging in transgenic Arabidopsis plants expressing luciferase under the control of the Zat12 promoter in response to different environmental stresses. B, RNA-blot analysis of luciferase and Zat12 steady-state transcript level in the plants shown in A in response to stress. Construction of transgenic plants, stress assays, and luciferase imaging were performed as described in “Materials and Methods.” Abbreviations: Luc, luciferase; PQ, methyl viologen (paraquat); rRNA, ribosomal RNA; RWC, relative water content.

Figure 2.

Systemic induction of the Zat12 promoter in response to wounding. A, Luciferase imaging in a transgenic Arabidopsis plant expressing luciferase under the control of the Zat12 promoter in response to wounding. Arrows indicate the wounded leaves. Luciferase imaging was performed at 0, 30, and 120 min following wounding. B, RNA-blot analysis of luciferase steady-state transcript level in transgenic Arabidopsis plant expressing luciferase under the control of the Zat12 promoter in response to wounding. Luciferase transcripts are shown to accumulate in local wounded leaves (lane 2) and systemic leaves of wounded plants (lane 4). Construction of transgenic plants, wounding, and luciferase imaging were performed as described in “Materials and Methods.” Abbreviations: Luc, luciferase; rRNA, ribosomal RNA.

Figure 3.

Tolerance of gain- and loss-of-function Zat12 Arabidopsis lines to abiotic stress. A, Root growth of wild-type and KO-Zat12 seedlings subjected to salinity stress. B, Root growth of wild-type and KO-Zat12 seedlings subjected to osmotic stress. C, Root growth of wild-type and KO-Zat12 seedlings subjected to heat stress. D, Root growth of wild-type and OE-Zat12 seedlings subjected to osmotic stress. Stress assays were performed as described in “Materials and Methods” using independent knockout and overexpression lines. Additional assays are shown in Supplemental Figures 1 and 2. Abbreviations: KO-Zat12-1, knockout Zat12, SALK_037357; KO-Zat12-2, knockout Zat12, SAIL 792_F04; OE-Zat12, transgenic seedlings overexpressing Zat12.

Figure 4.

RNA blots showing the expression of Zat12 and Apx1 in H₂O₂-treated and untreated wild-type plants and transgenic plants overexpressing Zat12. RNA blots were performed as described in “Materials and Methods.” Abbreviations: rRNA, ribosomal RNA; WT, wild type; Zat12, transgenic plants overexpressing Zat12.

Figure 5.

Venn diagrams showing the overlap between transcript expression in wild-type plants subjected to H₂O₂ stress (WT + H₂O₂), transgenic plants overexpressing Zat12 (Zat12), and transgenic plants overexpressing Zat12 subjected to H₂O₂ stress (Zat12 + H₂O₂). Transcriptome profiling and data analysis were performed as described in “Materials and Methods.”