Ethylene response factor ERF022 is involved in regulating Arabidopsis root growth

Ethylene response factors (ERFs) are involved in the regulation of plant development processes and stress responses. In this study, we provide evidence for the role of ERF022, a member of the ERF transcription factor group III, in regulating Arabidopsis root growth. We found that ERF022-loss-of-function mutants exhibited increased primary root length and lateral root numbers, and also morphological growth advantages compared to wild-type. Further studies showed that mutants had enhanced cell size in length in the root elongation zones. These results were accompanied by significant increase in the expression of cell elongation and cell wall expansion related genes SAUR10, GASA14, LRX2, XTH19 in mutants. Moreover, ERF022-mediated root growth was associated with the enhanced endogenous auxin and gibberellins levels. Our results suggest that loss-of-function of ERF022 up-regulated the expression of cell elongation and cell wall related genes through auxin and gibberellins signal in the regulation of root growth. Unexpectedly, ERF022 overexpression lines also showed longer primary roots and more lateral roots compared to wild-type, and had longer root apical meristematic zone with increased cell numbers. Overexpression of ERF022 significantly up-regulated cell proliferation, organ growth and auxin biosynthesis genes EXO, HB2, GALK2, LBD26, YUC5, which contribute to enhanced root growth. Altogether, our results provide genetic evidence that ERF022 plays an important role in regulating root growth in Arabidopsis thaliana.

The HAC1 histone acetyltransferase promotes leaf senescence and regulates the expression of ERF022

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.