Transcriptome profiling of the Chlamydomonas reinhardtii phot mutant
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ABSTRACT:
ORGANISM(S): Chlamydomonas reinhardtii
PROVIDER: GSE227473 | GEO | 2023/03/21
REPOSITORIES: GEO
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Project description:Green algae, such as Chlamydomonas reinhardtii, use light as an energy source, as well as a source of information. Light is processed by photoreceptors, such as phototropin, which subsequently send signals throughout the organism. Herein, a phosphoproteomic workflow is employed to charachterize signaling pathways of phototropin. For phosphopeptide enrichment, tryptic digests were diluted with 100 µL of acetonitrile. A Fe-IMAC column was equilibrated, and each sample was injected separately onto the column.
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Project description:Photosynthesis, the fundamental process using light energy to convert carbon dioxide to organic matter, is vital for life on Earth. It relies on capturing light through light-harvesting complexes (LHC) in photosystem I (PSI) and PSII and on the conversion of light energy into chemical energy. Composition and organization of PSI and PSII core complexes are well conserved across evolution. PSII is particularly sensitive to photodamage but benefits from a large diversity of photoprotective mechanisms, finely tuned to handle the dynamic and ever-changing light conditions. Light Harvesting Complex protein family members (LHC and LHC-like families) have acquired a dual function during evolution. Members of the LHC antenna complexes of PS capture light energy, whereas others dissipate excess energy that cannot be harnessed for photosynthesis. This process mainly occurs through nonphotochemical quenching (NPQ). In this work, we focus on the Light Harvesting complex-Like 4 (LHL4) protein, a LHC-like protein induced by ultraviolet-B (UV-B) and blue light through UV Resistance locus 8 (UVR8) and phototropin photoreceptor-activated signaling pathways in the model green microalgae Chlamydomonas reinhardtii. We demonstrate that alongside established NPQ effectors, LHL4 plays a key role in photoprotection, preventing singlet oxygen accumulation in PSII and promoting cell survival upon light stress. LHL4 protective function is distinct from that of NPQ-related proteins, as LHL4 specifically and uniquely binds to the transient monomeric form of the core PSII complex, safeguarding its integrity. LHL4 characterization expands our understanding of the interplay between light harvesting and photoprotection mechanisms upon light stress in photosynthetic microalgae.
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Project description:In photosynthetic organisms light acts as an environmental signal to control their development and physiology, and as energy source to drive the conversion of CO2 into carbohydrates used for growth or storage. The main storage carbohydrate in green algae is starch, which accumulates during the day and is broken down at night to meet cellular energy demands. The signalling role of light quality in the regulation of starch accumulation remains unexplored. Here, we report that in the model green alga Chlamydomonas reinhardtii blue light perceived by the photoreceptor PHOTOTROPIN suppresses starch accumulation. To gain more insight into the molecular mechanism underlying the PHOT-mediated light perception and starch accumulation, we applied we applied mass spectrometry (MS)-based quantitative proteomics to compare WT and phot cells grown in asynchronous photoautotrophic conditions under low light.
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Project description:Linear tetrapyrrole (bilin)-based phytochrome sensors optimize photosynthetic light capture by mediating massive gene reprogramming in land plants, yet surprisingly, many sequenced chlorophyte (green) algae lack phytochrome genes. Previous studies on the heme oxygenase (hmox1) mutant of Chlamydomonas reinhardtii suggest that bilin biosynthesis in plastids is needed for regulation of a limited nuclear gene network implicated in oxygen detoxification during dark to light transitions. The hmox1 mutant is unable to grow photoautotrophically and poorly acclimates to increased illumination even in the presence of acetate. Here we show that these phenotypes reflect the reduced accumulation of PSI reaction centers as well as a loss of PSI and PSII antennae complexes during photoacclimation. Phenotypically, the hmox1 mutant is similar to the chlorophyll biosynthesis mutants, gun4, crd1 and cth1. However, many of the hmox1 phenotypes can be rescued by the application of exogenous biliverdin IXα, the bilin product of HMOX1; this rescue is independent of photosynthesis but strongly dependent upon blue light. RNA-Seq comparisons of hmox1, 4A+ wild type and two genetically complemented lines also reveal that bilins restore regulation of a small network of photosynthesis-associated nuclear genes. These include genes responsible for chlorophyll biosynthesis (CHLI1/2), PSI light-harvesting (LHCA4) and naphthoquinone metabolism (MEN2), all of which show reduced photoinduction in the hmox1 mutant. We propose that a bilin-based, blue light sensory system is responsible for the maintenance of a functional photosynthetic apparatus in light-grown C. reinhardtii. This critical and possibly ancestral role for bilins may be responsible for retention of bilin biosynthesis in all eukaryotic photosynthetic species.
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Project description:Here, we report a transcriptomics analysis on a day in the life of Chlamydomonas reinhardtii. Cultures of this unicellular alga were grown in photobioreactors on a 12 h light / 12 h dark cycle. Samples were collected at regular intervals and subjected to a transcriptomics analysis by RNA-Seq.
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Project description:Transcriptome profiling of the Chlamydomonas reinhardtii phot mutant
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Project description:Light and temperature variations are inescapable in nature, providing many types of information and influencing development and physiology. PHOTOTROPIN (PHOT) blue light receptor-kinases play well-characterized roles in multiple processes in short time scales, but functions over days, weeks, or seasons have rarely been explored. Here we show that PHOT2 integrates blue light and low temperature signals to control leaf number at flowering. Plants lacking PHOT2 show delayed flowering, specifically when grown in low temperature. This effect is blocked by loss of NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3), and can be phenocopied by reduced blue light intensity, and by removal of CAMTA2. PHOT2 and CAMTA2 show non-additive genetic interactions, and a deep RNA-sequencing time course reveals highly overlapping phot2- and camta2-dependent effects on gene expression patterns across the day. Network-based co-expression analysis indicates system-level up-regulation of key growth modules in phot2 and camta2 mutants. Temperature- and genotype-dependent modulation of florigen-anti-florigen balance in phot2 and camta2 mutants is consistent with the phenotype. Together these data establish PHOT2 and NPH3 as a light-temperature coincidence detection module, operating with CAMTA2 as a downstream or parallel regulator of PHOT2-dependent gene expression.
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Project description:Light and temperature variations are inescapable in nature, providing many types of information and influencing development and physiology. PHOTOTROPIN (PHOT) blue light receptor-kinases play well-characterized roles in multiple processes in short time scales, but functions over days, weeks, or seasons have rarely been explored. Here we show that PHOT2 integrates blue light and low temperature signals to control leaf number at flowering. Plants lacking PHOT2 show delayed flowering, specifically when grown in low temperature. This effect is blocked by loss of NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3), and can be phenocopied by reduced blue light intensity, and by removal of CAMTA2. PHOT2 and CAMTA2 show non-additive genetic interactions, and a deep RNA-sequencing time course reveals highly overlapping phot2- and camta2-dependent effects on gene expression patterns across the day. Network-based co-expression analysis indicates system-level up-regulation of key growth modules in phot2 and camta2 mutants. Temperature- and genotype-dependent modulation of florigen-anti-florigen balance in phot2 and camta2 mutants is consistent with the phenotype. Together these data establish PHOT2 and NPH3 as a light-temperature coincidence detection module, operating with CAMTA2 as a downstream or parallel regulator of PHOT2-dependent gene expression.
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Project description:Photosynthetic organisms coordinate their metabolism and growth with diurnal light, which can range in intensity from limiting to inhibitory. To gain a comprehensive understanding of how diurnal regulatory circuits interface with sensing and response to various light intensities, we performed a systems analysis of synchronized Chlamydomonas reinhardtii populations acclimated to low, moderate, and high diurnal light. Transcriptomic and proteomic data revealed that Chlamydomonas’ rhythmic gene expression program is resilient to limiting and excess light. Although gene expression is dynamic over the diurnal cycle, Chlamydomonas populations acclimated to low and high diurnal light exhibit constitutive phenotypes with respect to photosystem abundance, thylakoid architecture, and non-photochemical quenching that persist through the night. This suggests that cells harbor a “memory” or anticipation of the daylight environment. The integrated data constitute an excellent resource for understanding gene regulatory mechanisms and photoprotection in eukaryotes under environmentally relevant conditions.
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