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A gene regulatory network involving the class II ERF transcriptional repressors in leaf senescence of Arabidopsis thaliana

ABSTRACT: Leaf senescence is the final developmental process that includes the mobilization of nutrients from old leaves to newly growing tissues. The progression of leaf senescence requires dynamic but coordinated changes of gene expression. Although several transcription factors (TFs) are known to be involved in both negative and positive modes of regulation of leaf senescence, detailed mechanisms that underlie the progression of leaf senescence are largely unknown. We report here that the class II ERF transcriptional repressors are controlled by proteasome and regulate the progression of leaf senescence in Arabidopsis. Since we had previously demonstrated that NtERF3, a model of tobacco class II ERFs, specifically interacts with a ubiquitin-conjugating enzyme, we examined the stability of NtERF3 and found that bacterially produced NtERF3 was rapidly degraded by plant protein extracts in vitro. Whereas NtERF3 accumulation was low in plants, it was increased by treatment with a proteasome inhibitor. Arabidopsis class II ERFs, namely, AtERF4 and AtERF8, were also controlled by proteasome and stabilized by aging of plants. The transgenic plants in which NtERF3, AtERF4, and AtERF8 were individually expressed under the control of the 35S promoter exhibited the precocious leaf senescence. Our microarray and RT-PCR analyses revealed that AtERF4 regulated expression of genes involving in various stress responses and leaf senescence. In contrast, aterf4 aterf8 mutant exhibited delayed leaf senescence. Taken together, we present the important role of class II ERFs in the regulation of leaf senescence.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE41053 | GEO | 2013/07/02

SECONDARY ACCESSION(S): PRJNA175634

REPOSITORIES: GEO

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Project description:Constituting the final growth phase during the lifecycle of maize (Zea Mays L.), leaf senescence plays an important biological role in grain yield in crops. We undertook proteomic and physiological analyses in inbred line Yu816 in order to unravel the underlying mechanisms of leaf senescence induced by preventing pollination. A total of 6,941 proteins were identified by Isobaric tags for Relative and Absolute Quantitation (iTRAQ) analysis. Proteomic analyses between pollinated (POL) and non-pollinated (NONPOL) plants indicated that 973 different proteins accumulated in NONPOL plants. The accumulated proteins were classified into various groups, including response to stimuli, cellular processes, cell death and metabolic processes using functional analysis. Furthermore, in accordance with the changes in these different accumulated proteins, analysis of changes in leaf total soluble sugars and starch content showed that the prevention of pollination can disturb endogenousplant hormone and sugar metabolism and lead to ROS bursts, protein degradation and photosystem breakdown, eventually resulting in leaf senescence. This represents the first attempt at global proteome profiling in response to induced leaf senescence by preventing pollination in maize, and provides a better understanding of the molecular mechanisms involved in induced leaf senescence.Constituting the final growth phase during the lifecycle of maize (Zea Mays L.), leaf senescence plays an important biological role in grain yield in crops. We undertook proteomic and physiological analyses in inbred line Yu816 in order to unravel the underlying mechanisms of leaf senescence induced by preventing pollination. A total of 6,941 proteins were identified by Isobaric tags for Relative and Absolute Quantitation (iTRAQ) analysis. Proteomic analyses between pollinated (POL) and non-pollinated (NONPOL) plants indicated that 973 different proteins accumulated in NONPOL plants. The accumulated proteins were classified into various groups, including response to stimuli, cellular processes, cell death and metabolic processes using functional analysis. Furthermore, in accordance with the changes in these different accumulated proteins, analysis of changes in leaf total soluble sugars and starch content showed that the prevention of pollination can disturb endogenousplant hormone and sugar metabolism and lead to ROS bursts, protein degradation and photosystem breakdown, eventually resulting in leaf senescence. This represents the first attempt at global proteome profiling in response to induced leaf senescence by preventing pollination in maize, and provides a better understanding of the molecular mechanisms involved in induced leaf senescence.

Project description:The aim of this experiment was to decipher a transcriptional regulatory code of Arabidopsis Auxin Response Factor 2 (ARF2) and understand the molecular basis of ARF2’s role as a promoter of dark-induced senescence. A combination of computational tools and yeast one-hybrid experiments identified potential direct transcriptional regulators of ARF2 belonging to several TF families including AP2/ERFs and AREB/ABF/ABI5s. Using ARF2 promoter mutants in transcriptional activation and Y1H experiments, the binding sites of these TFs in the ARF2 promoter were identified. AP2/ERFs including ERF1, ERF15 and ORA59 transactivate the ARF2 promoter in Arabidopsis mesophyll protoplasts and this transactivation is positively regulated by ABA. Crucially, the positive effect of ABA on ERF1 transactivation of ARF2 relies on the functional ABRE motif in the ARF2 promoter and the presence of AREB/ABF/ABI5s (ABF3 and ABF4) suggesting the existence of combinatorial regulation of ARF2 by these direct regulators. ABF3 and ABF4 were unable to activate the ARF2 promoter on their own indicating the necessity of ERF1 as a coupling TF for AREB/ABF/ABI5-driven regulation of ARF2. We also show that MED25 (a subunit of the Mediator complex) is required for proper transcriptional regulation of ARF2 during senescence. med25 plants show decreased ARF2 mRNA levels during natural senescence and, similarly to arf2-6 mutants, exhibit a delayed dark-induced senescence phenotype. We show that MED25 is important for ERF1-, ERF15- and ORA59-dependent transactivation of ARF2 in Arabidopsis protoplasts and finally idenitfy genes differentially expressed in arf2-6 mutants compared to wildtype during dark-induced senescence. Hence, we elucidate a regulatory network around ARF2 identifying combinatorial transcriptional regulation of this gene during senescence as well as likely downstream targets. The combinatorial regulation, comprised of AP2/ERFs and AREB/ABF/ABI5s TFs, enables integration of at least two key hormone signaling pathways to drive expression of a key senescence regulator.

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A gene regulatory network involving the class II ERF transcriptional repressors in leaf senescence of Arabidopsis thaliana

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