Abstract
Nutrient remobilization during leaf senescence nourishes the growing plant. Understanding the regulation of this process is essential for reducing our dependence on nitrogen fertilizers and increasing agricultural sustainability. Our laboratory is interested in chromatin changes that accompany the transition to leaf senescence. Previously, darker green leaves were reported for Arabidopsis thaliana hac1 mutants, defective in a gene encoding a histone acetyltransferase in the CREB‐binding protein family. Here, we show that two Arabidopsis hac1 alleles display delayed age‐related developmental senescence, but have normal dark‐induced senescence. Using a combination of ChIP‐seq for H3K9ac and RNA‐seq for gene expression, we identified 43 potential HAC1 targets during age‐related developmental senescence. Genetic analysis demonstrated that one of these potential targets, ERF022, is a positive regulator of leaf senescence. ERF022 is regulated additively by HAC1 and MED25, suggesting MED25 may recruit HAC1 to the ERF022 promoter to increase its expression in older leaves.
Highlights
We have previously shown a correlation between histone 3, lysine 4, trimethylation (H3K4me3) and histone 3, lysine 9 acetylation (H3K9ac) histone modifications and increased expression of senescence up-regulated genes (SURGs)
AtNAP encodes a positive regulator of leaf senescence associated with abscisic acid (ABA) synthesis (Liang et al, 2014; Yang et al, 2014)
The chlorophyll and gene expression data show that hac1 alleles display delayed leaf senescence
Summary
H3K27me3-target genes that continue to be expressed in clf/swn mutants are significantly enriched for leaf senescence-related GO terms, indicating that long-term dampening of SAG expression is mediated by the H3K27me repressive mark. Genes co-regulated by JA-ile and HAC1 were enriched for many defense-related biological process GO terms as well as leaf senescence. T-DNA insertion mutants in three potential HAC1 targets were tested for leaf senescence phenotypes, and an erf mutant disrupting the expression of ERF022 showed delayed senescence. AP2/ERF transcription factor as a novel positive effector of leaf senescence regulated by histone acetylation co-mediated by HAC1 and MED25
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