Project description:Photoperiod is a circannual signal measured by biological systems to align growth and reproduction with the seasons. To understand the effect of photoperiod of gene expression in Arabidopsis thaliana in the absence of exogenous sugar under constant light intensity, we performed time course mRNA-seq analysis on 13-day old seedlings across three photoperiods with triplicates to identify photoperiod-regulated genes.
Project description:The synchronization of the internal circadian clock with the external 24-h diurnal cycle is critical for ensuring optimal plant growth fitness. Despite lacking a DNA binding domain, LIGHT-REGULATED WD proteins (LWDs) are essential for sustaining and fine-tuning circadian rhythm1,2. However, the action mechanisms of how LWDs orchestrate the clock gene expressions remain largely elusive. We systematically identified 219 potential LWD1 protein partners at three Zeitgeber times (ZTs) using TurboID-mediated proximity labeling approach. A few LWD1-interacting epigenetic regulators are verified as new regulators of the Arabidopsis circadian clock, flowering time, and light-inhibited hypocotyl elongation. Our data also supports a new working model for LWD1-PSEUDO RESPONSE REGULATORS (PRRs)-TOPLESS (TPL) complex to repress the morning gene CIRCADIAN CLOCK ASSOCIATED (CCA1) in the late afternoon under diel cycles, shaping the expression trough of CCA1 in the late afternoon. Our results revealed a new co-repressor role of LWD1 by working with epigenetic regulators and transcription factors to underpin the precise operation of the circadian clock.
Project description:Although landscapes of several epigenetic marks are now available for Arabidopsis and rice, such profiles remain static and do not provide information about dynamic changes of plant epigenomes in response to developmental or environmental cues. Here we analyzed the effects of light regulation on four epigenetic histone modifications (H3K9ac, H3K9me3, H3K27ac, H3K27me3). Our genome-wide profiling of H3K9ac and H3K27ac revealed that these modifications are gene-specific. In contrast, we found that H3K9me3 and H3K27me3 target genes, but also intergenic-regions and transposable elements. Specific light conditions affected the number of epigenetically modified regions, as well as the overall correlation strength between the presence of specific epigenetic modifications and transcription. Futhermore, we observed that acetylation is an important contributor to light-regulated genome expression not only through its activating action on HY5 and HYH but also on their downstream targets. We found that dynamic acetylation changes in response to light have a major role in the active regulation of photosynthetic gene expression, while H3K27ac and H3K27me3 are major contributors to light regulation of the gibberellin metabolism. We also identified distinct epigenetic patterns in the epigenome of the photomorphogenic mutant cop1-4, suggesting that COP1 might have a role in the establishment of specific epigenetic modifications. Thus, this work provides a dynamic portrait of the variations in histone modifications in response to the plant’s changing light environment and strengthens the concept that epigenetic modifications represent another layer of control for light-regulated genes involved in photomorphogenesis.
Project description:Injured plant somatic tissues regenerate themselves by establishing the shoot or root meristems. In Arabidopsis (Arabidopsis thaliana) a two-step culture system ensures regeneration by first promoting the acquisition of pluripotency and subsequently specifying the fate of new meristems. Although previous studies have reported the importance of phytohormones auxin and cytokinin in determining the fate of new meristems, it remains elusive whether and how the environmental factors influence this process. In this study, we investigated the impact of light signals on shoot regeneration using Arabidopsis hypocotyl as explants. We found that light signals promote shoot regeneration while inhibiting root formation. ELONGATED HYPOCOTYL 5 (HY5), the pivotal transcriptional factor in light signaling, plays a central role in this process by mediating the expression of key genes controlling the fate of new meristems. Specifically, HY5 directly represses root development genes and activates shoot meristem genes, leading to the establishment of shoot progenitor from pluripotent callus. We further demonstrated that the early activation of photosynthesis is critical for shoot initiation, and this is transcriptionally regulated downstream of the HY5-dependent pathways. In conclusion, we uncovered the intricate molecular mechanisms by which light signals control the establishment of new meristem through the regulatory network governed by HY5, thus, highlighting the influence of light signals on plant developmental plasticity.