The phytochrome-interacting factor 4 (PIF4) is a well-known transcription factor that plays a pivotal role in plant thermomorphogenesis, coordinating growth and development in response to temperature changes. As PIF4 functions by forming complexes with other proteins, determining its interacting partners is essential for understanding its diverse roles in plant thermal responses. The GST (glutathione-S-transferase) pull-down assay is a widely used biochemical technique that enables the investigation of protein-protein interactions in vitro.
View Article and Find Full Text PDFMicroRNAs (miRNAs) play diverse roles in plant development, but whether and how miRNAs participate in thermomorphogenesis remain ambiguous. Here we show that HYPONASTIC LEAVES 1 (HYL1)-a key component of miRNA biogenesis-acts downstream of the thermal regulator PHYTOCHROME INTERACTING FACTOR 4 in the temperature-dependent plasticity of hypocotyl growth in Arabidopsis. A hyl1-2 suppressor screen identified a dominant dicer-like1 allele that rescues hyl1-2's defects in miRNA biogenesis and thermoresponsive hypocotyl elongation.
View Article and Find Full Text PDFWhile moderately elevated ambient temperatures do not trigger stress responses in plants, they do substantially stimulate the growth of specific organs through a process known as thermomorphogenesis. The basic helix-loop-helix transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) plays a central role in regulating thermomorphogenetic hypocotyl elongation in various plant species, including Arabidopsis (Arabidopsis thaliana). Although it is well known that PIF4 and its co-activator HEMERA (HMR) promote plant thermosensory growth by activating genes involved in the biosynthesis and signaling of the phytohormone auxin, the detailed molecular mechanism of such transcriptional activation is not clear.
View Article and Find Full Text PDFPhotoactivated phytochrome B (PHYB) binds to antagonistically acting PHYTOCHROME-INTERACTING transcription FACTORs (PIFs) to regulate hundreds of light responsive genes in Arabidopsis by promoting PIF degradation. However, whether PHYB directly controls the transactivation activity of PIFs remains ambiguous. Here we show that the prototypic PIF, PIF3, possesses a p53-like transcription activation domain (AD) consisting of a hydrophobic activator motif flanked by acidic residues.
View Article and Find Full Text PDFDaytime warm temperature elicits thermomorphogenesis in Arabidopsis by stabilizing the central thermoregulator PHYTOCHROME INTERACTING transcription FACTOR 4 (PIF4), whose degradation is otherwise promoted by the photoreceptor and thermosensor phytochrome B. PIF4 stabilization in the light requires a transcriptional activator, HEMERA (HMR), and is abrogated when HMR's transactivation activity is impaired in hmr-22. Here, we report the identification of a hmr-22 suppressor mutant, rcb-101, which surprisingly carries an A275V mutation in REGULATOR OF CHLOROPLAST BIOGENESIS (RCB).
View Article and Find Full Text PDFAmbient temperature has profound impacts on almost every aspect of plant growth and development, including seed germination, stem and petiole elongation, leaf movement, stomata development, flowering, and pathogen defense. Although the signal transduction pathways underlying plant responses to extreme cold and heat temperatures have been well studied, our understanding, at the molecular level, of how plants adjust phenotypic plasticity in response to nonstressful ambient temperature is still rudimentary. This review summarizes studies related to PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), the cardinal regulator of thermoresponsive growth in the model dicotyledonous plant Arabidopsis thaliana, emphasizing recent progress in the light-quality- and photoperiod-dependent regulation of PIF4-mediated thermomorphogenesis.
View Article and Find Full Text PDFAn amendment to this paper has been published and can be accessed via a link at the top of the paper.
View Article and Find Full Text PDFWarm temperature is postulated to induce plant thermomorphogenesis through a signaling mechanism similar to shade, as both destabilize the active form of the photoreceptor and thermosensor phytochrome B (phyB). At the cellular level, shade antagonizes phyB signaling by triggering phyB disassembly from photobodies. Here we report temperature-dependent photobody localization of fluorescent protein-tagged phyB (phyB-FP) in the epidermal cells of Arabidopsis hypocotyl and cotyledon.
View Article and Find Full Text PDFAmbient temperature sensing by phytochrome B (PHYB) in Arabidopsis is thought to operate mainly at night. Here we show that PHYB plays an equally critical role in temperature sensing during the daytime. In daytime thermosensing, PHYB signals primarily through the temperature-responsive transcriptional regulator PIF4, which requires the transcriptional activator HEMERA (HMR).
View Article and Find Full Text PDFPlant phytochromes are thought to transduce light signals by mediating the degradation of phytochrome-interacting transcription factors (PIFs) through the N-terminal photosensory module, while the C-terminal module, including a histidine kinase-related domain (HKRD), does not participate in signaling. Here we show that the C-terminal module of Arabidopsis phytochrome B (PHYB) is sufficient to mediate the degradation of PIF3 specifically and to activate photosynthetic genes in the dark. The HKRD is a dimerization domain for PHYB homo and heterodimerization.
View Article and Find Full Text PDFHEMERA (HMR) is a nuclear and plastidial dual-targeted protein. While it functions in the nucleus as a transcriptional coactivator in phytochrome signaling to regulate a distinct set of light-responsive, growth-relevant genes, in plastids it is known as pTAC12, which associates with the plastid-encoded RNA polymerase, and is essential for inducing the plastomic photosynthetic genes and initiating chloroplast biogenesis. However, the mechanism of targeting HMR to the nucleus and plastids is still poorly understood.
View Article and Find Full Text PDFPhytochromes (phys) are red and far-red photoreceptors that control plant development and growth by promoting the proteolysis of a family of antagonistically acting basic helix-loop-helix transcription factors, the PHYTOCHROME-INTERACTING FACTORs (PIFs). We have previously shown that the degradation of PIF1 and PIF3 requires HEMERA (HMR). However, the biochemical function of HMR and the mechanism by which it mediates PIF degradation remain unclear.
View Article and Find Full Text PDFPlant genomes are extremely sensitive to, and can be developmentally reprogrammed by environmental light cues. Here using rolling-circle amplification of gene-specific circularizable oligonucleotides coupled with fluorescence in situ hybridization, we demonstrate that light triggers a rapid repositioning of the Arabidopsis light-inducible chlorophyll a/b-binding proteins (CAB) locus from the nuclear interior to the nuclear periphery during its transcriptional activation. CAB repositioning is mediated by the red/far-red photoreceptors phytochromes (PHYs) and is inhibited by repressors of PHY signalling, including COP1, DET1 and PIFs.
View Article and Find Full Text PDFConnective tissue growth factor (CTGF), also known as CCN2, is a key proinflammatory mediator. In the present study, the involvement of the CTGF signaling pathway in human knee osteoarthritis (OA) fibroblast-like synoviocytes (FLSs) was investigated. FLSs were isolated from human OA synovium and incubated with CTGF in the absence or presence of interleukin‑1β (IL‑1β).
View Article and Find Full Text PDFPlant Signal Behav
August 2012
Since its initial discovery as a high affinity Ca ( 2+) -binding protein in the sarcoplasmic reticulum and endoplasmic reticulum (ER), calreticulin (CRT) has been documented to be a multifunctional protein in both animal and plant cells. This protein is well recognized as a Ca ( 2+) -binding molecular chaperone that facilitates the folding of newly synthesized glycoproteins and regulates the Ca ( 2+) homeostasis in the ER lumen. However, functional relevance associated with its localization in other cellular compartments has also been reported.
View Article and Find Full Text PDFCalcium/calmodulin (Ca(2+)/CaM) has long been considered a crucial component in wound signaling pathway. However, very few Ca(2+)/CaM-binding proteins have been identified which regulate plant responses to herbivore attack/wounding stress. We have reported earlier that a family of Ca(2+)/CaM-binding transcription factors designated as AtSRs (also known as AtCAMTAs) can respond differentially to wounding stress.
View Article and Find Full Text PDFGT factors are a family of plant-specific transcription factors with conserved trihelix DNA-binding domains that bind GT elements. By screening a cDNA expression library with (35)S-labeled recombinant calmodulin (CaM), we identified AtGT2L, a classic member of GT-2 subfamily, as a Ca(2+)-dependent CaM-binding protein. AtGT2L specifically targets the nucleus and possesses both transcriptional activation and DNA-binding abilities, implicating its function as a nuclear transcription factor.
View Article and Find Full Text PDFCalreticulin (CRT) is an endoplasmic reticulum-resident calcium-binding molecular chaperone that is highly conserved in multi-cellular eukaryotes. Higher plants contain two distinct groups of CRTs: CRT1/CRT2 and CRT3 isoforms. Previous studies have shown that bacterial elongation factor Tu receptor (EFR), a pattern-recognition receptor that is responsible for pathogen-associated molecular pattern-triggered immunity, is a substrate for Arabidopsis CRT3, suggesting a role for CRT3 in regulating plant defense against pathogens.
View Article and Find Full Text PDF