Abstract
Plants respond to reductions in internal oxygen concentrations with adaptive mechanisms (for example, modifications of metabolism to cope with reduced supply of ATP). These responses are, at the transcriptional level, mediated by the group VII Ethylene Response Factor transcription factors, which have stability that is regulated by the N-end rule pathway of protein degradation. N-end rule pathway mutants are characterized by a constitutive expression of hypoxia response genes and abscisic acid hypersensitivity. Here, we identify a novel proteolysis6 (prt6) mutant allele, named greening after extended darkness1 (ged1), which was previously discovered in a screen for genomes uncoupled-like mutants and shows the ability to withstand long periods of darkness at the seedling stage. Interestingly, this ethyl methanesulfonate-derived mutant shows unusual chromosomal rearrangement instead of a point mutation. Furthermore, the sensitivity of N-end rule pathway mutants ged1 and prt6-1 to submergence was studied in more detail to understand previously contradicting experiments on this topic. Finally, it was shown that mutants for the N-end rule pathway are generally more tolerant to starvation conditions, such as prolonged darkness or submergence, which was partially associated with carbohydrate conservation.
Highlights
Plants respond to reductions in internal oxygen concentrations with adaptive mechanisms
Stabilization of VII Ethylene Response Factor (VII-ERF) during hypoxia activates the transcription of downstream hypoxia-responsive genes, including those involved in fermentation and sugar consumption (Gibbs et al, 2011; Licausi et al, 2011)
Gibbs et al (2011) treated 7-d-old seedlings grown on Murashige and Skoog (MS) medium supplemented with 1% (w/v) Suc with argon gas in darkness for 9 and 12 h and reported a higher survival of the mutants compared with the wild type
Summary
Plants respond to reductions in internal oxygen concentrations with adaptive mechanisms (for example, modifications of metabolism to cope with reduced supply of ATP). The transcriptional regulation of flooding-adaptive genes operates through a specific signal transduction pathway triggered by a decline in the cellular oxygen concentration This oxygen-sensing mechanism is mediated by the oxygen- and nitric oxide-dependent degradation of subgroup VII Ethylene Response Factor (VII-ERF) transcription factors through the N-end rule pathway of proteolysis (Gibbs et al, 2011, 2014; Licausi et al, 2011). Genevestigator.com/gv/plant.jsp; Hruz et al, 2008), we identified a mutant that is characterized by a constitutively high expression of hypoxia-responsive genes, similar to prt, ate1/ate, and pco1/pco (Gibbs et al, 2011; Weits et al, 2014) We hypothesized that this mutant, greening after extended darkness (ged1), is disturbed in the hypoxic signal transduction pathway. Altered ABA sensitivity has been described for N-end rule pathway mutants (Holman et al, 2009; Gibbs et al, 2014)
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