Project description:Elongator is a histone acetyltransferase (HAT) complex associated with RNA polymerase II (RNAPII) to facilitate transcription elongation. It consists of subunits Elp1-6, with Elp3 conferring HAT activity. Elongator is conserved in yeast, plants and humans. In humans, mutations in Elp genes cause neuronal diseases. In plants, Elongator is a positive regulator of cell proliferation during leaf and root growth. Consequently, Arabidopsis Elongator mutants (elo) have narrow leaves and short roots; additionally, germination, vegetative growth and reproductive development are also affected. Mutants have altered auxin signaling, and a number of auxin-related genes are among those differentially expressed in the mutant. Only two genes have been confirmed as targeted by Elongator during RNAPII transcription elongation, including the light-regulated auxin response regulator IAA3/SHY2.
Project description:Environmental stimuli-triggered stomatal movement is a key physiological process that regulates CO<sub>2</sub> uptake and water loss in plants. Stomata are defined by pairs of guard cells that perceive and transduce external signals, leading to cellular volume changes and consequent stomatal aperture change. Within the visible light spectrum, red light induces stomatal opening in intact leaves. However, there has been debate regarding the extent to which red-light-induced stomatal opening arises from direct guard cell sensing of red light versus indirect responses as a result of red light influences on mesophyll photosynthesis. Here we identify conditions that result in red-light-stimulated stomatal opening in isolated epidermal peels and enlargement of protoplasts, firmly establishing a direct guard cell response to red light. We then employ metabolomics workflows utilizing gas chromatography mass spectrometry and liquid chromatography mass spectrometry for metabolite profiling and identification of Arabidopsis guard cell metabolic signatures in response to red light in the absence of the mesophyll. We quantified 223 metabolites in Arabidopsis guard cells, with 104 found to be red light responsive. These red-light-modulated metabolites participate in the tricarboxylic acid cycle, carbon balance, phytohormone biosynthesis and redox homeostasis. We next analyzed selected Arabidopsis mutants, and discovered that stomatal opening response to red light is correlated with a decrease in guard cell abscisic acid content and an increase in jasmonic acid content. The red-light-modulated guard cell metabolome reported here provides fundamental information concerning autonomous red light signaling pathways in guard cells.
Project description:The cold acclimation process is regulated by many factors like ambient temperature, day length, light intensity, or hormonal status. Experiments with plants grown under different light-quality conditions indicate that the plant response to cold is also a light-quality-dependent process. Here, the role of light quality in the cold response was studied in one-month-old Arabidopsis thaliana (Col‐0) plants exposed for one week to 4 °C at short‐day conditions under white (100 and 20 μmol m‐2s‐1), blue or red (20 μmol m‐2s‐1) light conditions. An upregulated expression of CBF1, an inhibition of photosynthesis, and an increase in membrane damage showed that blue light enhanced the effect of low temperature. Interestingly, cold-treated plants under blue and red light showed only limited freezing tolerance compared to white light cold-treated plants. Next, the specificity of the light quality signal in cold response was evaluated in Arabidopsis accessions originating from different and contrasting latitudes. In all but one Arabidopsis accessions, blue light increased the effect of cold on photosynthetic parameters and electrolyte leakage. This effect was not found for Ws-0, which lacks functional CRY2 protein, indicating its role in the cold response. Proteomics data confirmed significant differences between red and blue light treated plants at low temperature and showed that the cold response is highly accession specific. In general, blue light increased mainly the cold-stress related proteins and red light induced higher expression of chloroplast-related proteins, which correlated with higher photosynthetic parameters in red light cold-treated plants. Altogether, our data suggest that light modulates two distinct mechanisms during the cold treatment - red light driven cell function maintaining program and blue light activated specific cold response. The importance of mutual complementarity of these mechanisms was demonstrated by significantly higher freezing tolerance of cold-treated plants under white light.
Project description:Thiol-based redox regulation is a crucial post-translational mechanism to acclimate plants to changing light availability. Here, we conduct a biotin-switch-based redox proteomics study to systematically investigate dynamics of the thiol-redox network in response to temporal changes in light availability and across genotypes lacking parts of the NTRC/thioredoxin (Trx) systems in the chloroplast. Temporal dynamics revealed light leading to marked decreases in the oxidation states of 75 chloroplast proteins mainly involved in photosynthesis during the first 10 min, followed by their partial re-oxidation after 2-6 hours into the photoperiod. This involved f, m and x-type Trx proteins showing similar light-induced reduction-oxidation dynamics, while NTRC, 2-Cys-Prx and Trx y2 showed an opposing pattern, being more oxidized in the light, compared to the dark. In Arabidopsis trxf1f2, trxm1m2 or ntrc mutants, most protein candidates showed increased oxidation states, compared to the wild type, suggesting their light-dependent dynamics to be related to the NTRC/Trx network. In this context, deficiencies in f- and m-type Trxs were found to have different impacts on the thiol-redox proteome depending on the light environment, being higher in constant and fluctuating light, respectively, while NTRC deficiency having a strong influence in all light conditions. Results indicate the plant redox proteome to be subject to dynamic changes in reductive and oxidative pathways to cooperatively fine-tune photosynthetic and metabolic processes in the light. This involves f-type Trxs and NTRC to play a role in constant light conditions, while both m-type Trxs and NTRC being important to balance changes in protein redox-pattern during dynamic alterations in fluctuating light intensities.
Project description:Investigation of whole genome gene expression level changes in Arabidopsis roots by the effect of light. Plant growth is sustained by a continuous cell division in meristems followed by cell differentiation and elongation. We have found that in Arabidopsis thaliana roots, flavonols play a key role in regulating the transition from cell division to differentiation. Using an engineered device to grow roots in darkness, but shoot in light cycle, coupled with transcriptomic and metabolomics analysis, we deciphered that flavonols accumulation regulates proliferation-promoting levels of auxin-PLETHORA and superoxide anion (O2-). High flavonols levels restrict auxin transport and the PLETHORA gradient but also superoxide radical content, promoting an accelerated cell differentiation. Furthermore, cytokinin-SHY2 and H2O2-UPB1 pathways, which promote differentiation and, respectively, antagonize auxin and O2- activity, increase flavonols biosynthesis establishing mutual interactions among these pathways. Flavonols function as positional signals integrating hormonal and ROS pathways to determine final organ growth. This work analyze the effect of root illumination in gene transcription. Details of how plants and roots are grown are described in Silva et al. (submitted) A six chip study using total RNA extracted from three independent experiments of Arabidopsis roots growing in presence of light and three independent experiments of Arabidopsis roots growing without light.
Project description:In this study we used proteomics, metabolomics and reverse genetics to investigate how different light environmental factors such as intensity or variability affect long-term and short-term acclimation responses of Arabidopsis and the importance of the chloroplast redox network in their regulation.
Project description:Sun-loving plants have the ability to detect and avoid shading through sensing of both blue and red light wavelengths. Higher plant cryptochromes (CRYs) control how plants modulate growth in response to changes in blue light. For growth under a canopy, where blue light is diminished, CRY1 and CRY2 perceive this change and respond by directly contacting two bHLH transcription factors, PIF4 and PIF5. These factors are also known to be controlled by phytochromes, the red/far-red photoreceptors; however, transcriptome analyses indicate that the gene regulatory programs induced by the different light wavelengths are distinct. Our results indicate that CRYs signal by modulating PIF activity genome-wide, and that these factors integrate binding of different plant photoreceptors to facilitate growth changes under different light conditions. We performed whole-genome transcriptome (mRNA-seq) analysis on 5-day-old Arabidopsis thaliana Columbia wild-type (WT) and pif4pif5 seedlings exposed to low blue-light (LBL) or mock-treated for 1, 6 and 24 hours. In addition we performed mRNA-seq on WT, 35S::PIF4-9xMyc-6x-His-3xFlag(Flash) and 35S::PIF5-9xMyc-6x-His-3xFlag (Flash) seedlings treated with LBL or mock-treated for 16 hours.
Project description:To understand the transcript regulation of early Arabidopsis seedlings developments with different chemicals under continuous blue light irradiation.
Project description:Phytochromes are red/far-red light photoreceptors. We sought to test at the transcriptomic level if Arabidopsis mutants lacking all phytochromes (from phyA to phyE), or just retaining trace levels of phyC, had transcriptional response to red light exposure.