A reporter gene system used to study developmental expressionof alternative oxidase and isolate mitochondrial retrograde regulationmutants in Arabidopsis

Abstract

Perturbation of mitochondrial function causes altered nuclear gene expression in plants. To study this response, called mitochondrial retrograde regulation, and developmental gene expression, a transgenic Arabidopsis thaliana (Col-0) line containing a firefly luciferase gene controlled by a promoter region of the Arabidopsis alternative oxidase 1a gene (AtAOX1a) was created. The transgene and the endogenous gene were developmentally induced in young cotyledons to a level higher than in older cotyledons and leaves. Analysis of transgene expression suggests that this is true for emerging leaves as well. Antimycin A (AA), a mitochondrial electron transport chain inhibitor, and monofluroacetate (MFA), a TCA cycle inhibitor, induced expression of the transgene and the endogenous gene in parallel. The following comparative responses of the transgene to inhibitors were observed: (a) the response in cotyledons to AA treatment differed greatly in magnitude from the response in leaves; (b) the induction kinetics in cotyledons following MFA treatment differed greatly from the kinetics in leaves; and (c) the induction kinetics following MFA treatment differed from the kinetics of AA in both leaves and cotyledons. The transgenic line was used in a genetic screen to isolate mutants with greatly decreased transgene and AtAOX1a induction in response to AA. Some of these mutant lines showed greatly decreased induction by MFA, but one did not. Taken altogether, the data provide genetic evidence that suggests that induction of the AtAOX1a gene by distinct mitochondrial perturbations are via distinct, but overlapping signaling pathways that are tissue specific.

Mitochondrial Reactive Oxygen Species. Contribution to Oxidative Stress and Interorganellar Signaling

“…At least for the Arabidopsis AOX1a gene, induction is most likely the result of increased transcription controlled at a promoter region (Dojcinovic et al, 2005;Zarkovic et al, 2005).…”

How do plants make mitochondria?

“…While a genetic system to elucidate these factors has been described (Zarkovic et al 2005), no factors using this system have been described as yet. Other approaches have identiWed the transcription factor ABI4 as a regulator of alternative oxidase ), where ABI4 acts as a repressor of alternative oxidase transcription, thus, upon stress treatment the alternative oxidase expression is repressed.…”

Two Zinc-Cluster Transcription Factors Control Induction of Alternative Oxidase in Neurospora crassa

“…Individual genes within the family are expressed differentially in response to a variety of stresses or developmental signals (reviewed in Vanlerberghe and McIntosh 1997;ArnholdtSchmitt et al 2006;Clifton et al 2006;Rhoads et al 2006;Rhoads and Subbaiah 2007). For at least some genes in some species, it has been shown that expression likely involves control at the level of transcription, although additional controls at the level of mRNA stability and translation may also exist (Yu et al 2001;Thirkettle-Watts et al 2003;Dojcinovic et al 2005;Zarkovic et al 2005). In T. brucei, the level of alternative 1 oxidase is controlled post-transcriptionally in a developmentally regulated fashion (Chaudhuri et al 2002).…”

“…More broadly based mutant screens have been performed in Arabidopsis thaliana and Neurospora crassa. In A. thaliana, several genes were found that are required to induce the alternative oxidase, most likely at the level of transcription, in response to either antimycin A or monofluroacetate, an inhibitor of the Kreb's cycle (Zarkovic et al 2005). In N. crassa, alternative oxidase is encoded by the alternative oxidase (aod-1) gene.…”