Biology subjects

Ruiz-Sola, M. A.

Publications and source records attributed to Ruiz-Sola, M. A..

5 recordsLinked to original sources

bioRxiv2025

The yellow-in-the-dark chIL Chlamydomonas mutant as a model for time-resolved chloroplast biogenesis and physiological responses to lincomycin

Understanding chloroplast biogenesis is key given the importance of photosynthesis and chloroplast metabolism. Chloroplast assembly has been extensively studied in angiosperms, where the main hallmarks have been established, including the need for nuclear and plastid genome coordination through anterograde and retrograde signals. However, recent works in other photosynthetic lineages have revealed both divergent and conserved regulators. These differences likely represent adaptive strategies that emerged during the evolution of the green lineage, and highlight the need for evolutionary studies to fully elucidate the mechanisms controlling chloroplast biogenesis, a light-promoted process. Here, we characterize the yellow-in-the-dark chIL mutant of Chlamydomonas reinhardtii, which carries a mutation in the CHLL subunit of the dark-operative POR enzyme. Dark-adapted chIL cells cannot synthesize chlorophylls and display a de-differentiated chloroplast, and our results show that upon exposure to light, chloroplast biogenesis is initiated very rapidly based on starch reserves. We demonstrate that accumulation of pigments, photosynthesis-related proteins, and functional chloroplast activity is detected within 1-3 hours of illumination. Additionally, we show that lincomycin, an inhibitor of plastid translation, specifically affects chloroplast physiology, and blocks light-induced chloroplast biogenesis and cell growth, establishing lincomycin as a valuable tool for investigating chloroplast physiology and plastid-to-nucleus signals in Chlamydomonas. Together, this study introduces the chIL mutant as a powerful model system to dissect light-induced, time-resolved chloroplast biogenesis, as well as the responses and signaling triggered by lincomycin. By promoting broader adoption of this model, we aim to help inform strategies to enhance photosynthesis and stress tolerance, and optimize bioproduct production.

plant biology↗

bioRxiv2024

Beyond the phloem: A general role of the Arabidopsis OCTOPUS gene family in controlling plant growth vigour

OCTOPUS (OPS) and OCTOPUS-LIKE 2 (OPL2), two homologous genes, were previously identified as important regulators of phloem differentiation in Arabidopsis roots, impacting root growth when their function is lost. Here, we investigated the roles of the other three OPS homologs in Arabidopsis, OPL1, OPL3, and OPL4. We employed promoter activity analyses, protein localisation studies, functional complementation assays, analysis of single and multiple mutant combinations, and growth assays, including exposure to CLE45 and brassinosteroid pathway modulators. The OPS/OPL genes exhibit overlapping expression patterns and functions. Multiple mutant combinations revealed a high degree of redundancy, with OPS and the phloem domain playing a major role in controlling plant growth. While phloem phenotypes are not exacerbated in higher-order mutants, plant growth vigour is nevertheless more severely impacted than in ops opl2. Our results suggest a novel role of the OPS/OPL genes in broadly controlling plant growth and development, potentially through the modulation of meristematic activity via brassinosteroid pathways.

plant biology↗

bioRxiv2024

Phototropin connects blue light perception to starch metabolism in green algae

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 identify PHOTOTROPIN-MEDIATED SIGNALLING KINASE 1 (PMSK1) as a key regulator of starch metabolism in Chlamydomonas reinhardtii. In its phosphorylated form (PMSK1-P), it activates GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE (GAP1), promoting starch biosynthesis. We show that blue light, perceived by PHOTOTROPIN, induces PMSK1 dephosphorylation that in turn represses GAP1 mRNA levels and reduces starch accumulation. These findings reveal a novel blue light-mediated signaling pathway that advances our understanding of photoreceptor-controlled carbon metabolism in microalgae. One-Sentence SummaryBlue light perception by PHOTOTROPIN triggers kinase-mediated signaling to inhibit starch accumulation in the green alga Chlamydomonas.

plant biology↗

bioRxiv2021

Photoprotection is regulated by light-independent CO2 availability

Photosynthetic algae have evolved mechanisms to cope with suboptimal light and CO2 conditions. When light energy exceeds CO2 fixation capacity, Chlamydomonas reinhardtii activates photoprotection, mediated by LHCSR1/3 and PSBS, and the CO2 Concentrating Mechanism (CCM). How light and CO2 signals converge to regulate these processes remains unclear. Here, we show that excess light activates photoprotection- and CCM-related genes by altering intracellular CO2 concentrations and that depletion of CO2 drives these responses, even in total darkness. High CO2 levels, derived from respiration or impaired photosynthetic fixation, repress LHCSR3/CCM genes while stabilizing the LHCSR1 protein. Finally, we show that the CCM regulator CIA5 also regulates photoprotection, controlling LHCSR3 and PSBS transcript accumulation while inhibiting LHCSR1 protein accumulation. This work has allowed us to dissect the effect of CO2 and light on CCM and photoprotection, demonstrating that light often indirectly affects these processes by impacting intracellular CO2 levels.

plant biology↗

bioRxiv2020

GUN1-independent retrograde signaling targets the ethylene pathway to repress photomorphogenesis

When germinating in the light, Arabidopsis seedlings undergo photomorphogenic development, characterized by short hypocotyls, greening and expanded cotyledons. Stressed chloroplasts emit retrograde signals to the nucleus that induce developmental responses and repress photomorphogenesis. The nuclear targets of these retrograde signals are not yet fully known. Here, we show that lincomycin-treated seedlings (which lack developed chloroplasts) show strong phenotypic similarities to seedlings treated with ethylene (ET) precursor 1-aminocyclopropane-1-carboxylic acid (ACC), as both signals inhibit cotyledon separation in the light. We show that the lincomycin-induced phenotype partly requires a functioning ET signaling pathway, but could not detect increased ET emissions in response to lincomycin treatment. The two treatments show overlap in up-regulated gene transcripts, downstream of transcription factors ETHYLENE INSENSITIVE3 (EIN3) and EIN3-LIKE1 (EIL1). The induction of the ethylene signaling pathway is triggered by an unknown retrograde signal acting independently of GENOMES UNCOUPLED1 (GUN1). Our data show how two apparently different stress responses converge to optimize photomorphogenesis. One Sentence SummaryChloroplast retrograde signaling targets the ethylene-regulated gene network to repress photomorphogenesis in Arabidopsis

plant biology↗