Biology subjects

Leung, C. C.

Publications and source records attributed to Leung, C. C..

5 recordsLinked to original sources

bioRxiv2023

The circadian clock regulates PIF3 protein stability in parallel to red light

The circadian clock is an endogenous oscillator, but its importance lies in its ability to impart rhythmicity on downstream biological processes or outputs. Focus has been placed on understanding the core transcription factors of the circadian clock and how they connect to outputs through regulated gene transcription. However, far less is known about posttranslational mechanisms that tether clocks to output processes through protein regulation. Here, we identify a protein degradation mechanism that tethers the clock to photomorphogenic growth. By performing a reverse genetic screen, we identify a clock-regulated F-box type E3 ubiquitin ligase, CLOCK-REGULATED F-BOX WITH A LONG HYPOCOTYL 1 (CFH1), that controls hypocotyl length. We then show that CFH1 functions in parallel to red light signaling to target the transcription factor PIF3 for degradation. This work demonstrates that the circadian clock is tethered to photomorphogenesis through the ubiquitin proteasome system and that PIF3 protein stability acts as a hub to integrate information from multiple environmental signals.

plant biology↗

bioRxiv2023

Parallel mechanisms detect different photoperiods to independently control seasonal flowering and growth in plants

For nearly 100 years, we have known that both growth and flowering in plants are seasonally regulated by the length of the day (photoperiod). Intense research focus and powerful genetic tools have propelled studies of photoperiodic flowering, but far less is known about photoperiodic growth, in part because tools were lacking. Here, using a new genetic tool that visually reports on photoperiodic growth, we identified a seasonal growth regulation pathway, from photoperiod detection to gene expression. Surprisingly, this pathway functions in long days but is distinct from the canonical long day photoperiod flowering mechanism. This is possible because the two mechanisms detect the photoperiod in different ways: flowering relies on measuring photoperiod by directly detecting duration of light intensity while the identified growth pathway relies on measuring photosynthetic period indirectly by detecting the duration of photosynthetic metabolite production. In turn, the two pathways then control expression of genes required for flowering or growth independently. Finally, our tools allow us to show that these two types of photoperiods, and their measurement systems, are dissociable. Our results constitute a new view of seasonal timekeeping in plants by showing that two parallel mechanisms measure different photoperiods to control plant growth and flowering, allowing these processes to be coordinated independently across seasons.

plant biology↗

bioRxiv2022

Diverse photoperiodic gene expression patterns are likely mediated by distinct transcriptional systems in Arabidopsis

Photoperiod is an annual cue measured by biological systems to align growth and reproduction with the seasons. In plants, photoperiodic flowering has been intensively studied for over 100 years, but we lack a complete picture of the transcriptional networks and cellular processes that are photoperiodic. We performed a transcriptomics experiment on Arabidopsis plants grown in 3 different photoperiods, and find that nearly one-third of the known genes show photoperiodic alteration in gene expression. Gene clustering, daily expression integral calculations and cis-element analysis then separate photoperiodic genes into co-expression subgroups that display 19 diverse seasonal expression patterns, opening the possibility that many photoperiod measurement systems work in parallel in Arabidopsis. Then, functional enrichment analysis predicts co-expression of important cellular pathways. To test these predictions, we generated a comprehensive catalog of genes in the phenylpropanoid biosynthesis pathway, overlaid gene expression data and demonstrated that photoperiod intersects with the two major phenylpropanoid pathways differentially, controlling flavonoids but not lignin. Finally, we describe the development of a new app that visualizes photoperiod transcriptomic data for the wider community.

plant biology↗

bioRxiv2020

A metabolic coincidence mechanism controls winter photoperiodism in plants

Plants have served as a preeminent study system for photoperiodism because of their propensity to flower in concordance with the seasons. A nearly singular focus on understanding seasonal flowering has been to the detriment of discovering other photoperiod measuring mechanisms that may be necessary for vegetative health. Here we use bioinformatics to identify a group of winter photoperiod-induced genes in Arabidopsis and show that one, PP2-A13, is critical for fitness and survival, exclusively in winter-like photoperiods. We create a real-time photoperiod reporter, using the PP2-A13 promoter driving luciferase, and show that winter photoperiod genes are regulated independent of the canonical CO/FT mechanism for photoperiodic flowering. The reporter then allows us to identify the first genetic and cellular drivers of winter photoperiodism and reveal a mechanism that relies on coincidence between light capture through photosynthesis and rhythmic metabolism. This work demonstrates that plants have distinct photoperiod measuring mechanisms that enact critical biological and developmental processes in different seasons.

plant biology↗

bioRxiv2020

Characterization of Stanniocalcin-1 Expression in Macrophage Differentiation

Human stanniocalcin-1 (STC1) is a paracrine factor associated with inflammation and carcinogenesis. The role of STC1 in the pro- and anti-inflammatory functions of differentiating macrophage, however, is not clear. In this study, our data showed that PMA treatment induced human leukemia monocytic cells (ThP-1) differentiation to M0 macrophages. The differentiation was accompanied by a significant increase of mRNA expression levels of STC1, the pro-inflammatory cytokine TNF, and anti-inflammatory markers, CD163 & CD206. An intermitted removal of PMA treatment reduced the mRNA levels of STC1 and TNF but had no noticeable effects on the anti-inflammatory markers. The correlation in the expression of STC1 and pro-inflammatory markers in differentiating macrophages was investigated, using siRNASTC1-transfected PMA-induced cells. Consistently, the transcripts levels of TNF and IL-6 were significantly reduced. Moreover, LPS/IFN{gamma}-induced M1-polarization showed remarkably higher expression levels of STC1 than IL-4/IL-13-induced M2-macrophages and PMA-induced M0-macrophages. Transcriptomic analysis of siRNASTC1-transfected M1-polarized cells revealed an upregulation of TBC1 domain family member 3 (TBC1D3G). The gene regulates the payload of macrophage-released extracellular vesicles to mediate inflammation. The conditioned media from siRNASTC1-transfected M1-polarized cells were found to reduce Hep3B cell motility. The data suggest that the expression of STC1 were associated with macrophage differentiation, but preferentially to M1 polarization.

cell biology↗