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Cell-type specific UVB-mediated changes of VcUVR8 and COP1 transcript level. Reproductive and somatic cell types were incubated under UV-B light (0.056 mW/cm²) supplemented with 0.8 µmol m− 2 s− 1 white light (WL + UVB). Control cells were incubated under UV-B exclusion (WL). Each experiment was performed in triplicate from at least two different biological samples. The data were averaged and statistically treated (t test, **P < 0.01). Bars show means and standard deviations
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A fundamental question in biology is how multicellular organisms regulate cellular and physiological processes in response to environmental signals in a tissue/cell type-specific manner. Light is one such cue but little is known about its effect on molecular mechanisms underlying cell-type specific signaling. The Volvox genus presents a Germ-Soma d...
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Germ-soma differentiation evolved independently in many eukaryotic lineages and contributed to complex multicellular organizations. However, the molecular genetic bases of such convergent evolution remain unresolved. Two multicellular volvocine green algae, Volvox and Astrephomene , exhibit convergent evolution of germ-soma differentiation. The com...
Citations
... There were also pronounced reactions related to protein degradation and folding, especially factors with chaperone-like functions. This includes homologs of the mitochondrial GrpE2 protein and ABC transporter 1 (Cardazzo et al., 1998), both of which were shown to be triggered by UV-B in plants and algae such as A. thaliana and Volvox carteri (Razeghi and Kianianmomeni, 2019), respectively. A specific search for differentially expressed heat shock protein (HSP) sequences in the Serritaenia transcriptome revealed 11 upregulated HSP genes (Supplementary Table S4), all predicted to act as molecular chaperones assisting in a wide range of folding processes of proteins (Mayer and Bukau, 2005;Qiu et al., 2006;Guo et al., 2020). ...
... Two Chl a/b-binding proteins (ELIP, early lightinduced protein; and SEP2, stress enhanced protein 2), for example, accumulate upon UV-B exposure in vascular plants and prevent excess accumulation of free chlorophyll, thereby protecting against photo-oxidative damage (Heddad and Adamska, 2000;Hutin et al., 2003;Sävenstrand et al., 2004). These factors have also been found in chlorophyte green algae such as V. carteri (Razeghi and Kianianmomeni, 2019) and C. reinhardtii (Allorent and Petroutsos, 2017), and might represent a universal mechanism in the green chloroplasts of the Viridiplantae at least. Similar to these other organisms, Serritaenia has several ELIP genes, most of which, however, were not upregulated. ...
The zygnematophytes are the closest relatives of land plants and comprise several lineages that adapted to a life on land. Species of the genus Serritaenia form colorful, mucilaginous capsules, which surround the cells and block harmful solar radiation, one of the major terrestrial stressors. In eukaryotic algae, this “sunscreen mucilage” represents a unique photoprotective strategy, whose induction and chemical background are unknown. We generated a de novo transcriptome of Serritaenia testaceovaginata and studied its gene regulation under moderate ultraviolet radiation (UVR) that triggers sunscreen mucilage under experimental conditions. UVR induced the repair of DNA and the photosynthetic apparatus as well as the synthesis of aromatic specialized metabolites. Specifically, we observed pronounced expressional changes in the production of aromatic amino acids, phenylpropanoid biosynthesis genes, potential cross-membrane transporters of phenolics, and extracellular, oxidative enzymes. Interestingly, the most upregulated enzyme was a secreted class III peroxidase, whose embryophyte homologs are involved in apoplastic lignin formation. Overall, our findings reveal a conserved, plant-like UVR perception system (UVR8 and downstream factors) in zygnematophyte algae and point to a polyphenolic origin of Serritaenia’s sunscreen pigment, whose synthesis might be extracellular and oxidative, resembling that of plant lignins.
... Due to the destruction of the stratospheric ozone layer since 1970, the level of solar ultraviolet (UV) radiation that passes through the atmosphere and reaches the earth surface is increasing. Some ecosystems and many aquatic organisms are affected by this increase (Razeghi and Kianianmomeni 2019;Sun et al. 2021). In recent years, ozone depletion has become a significant concern. ...
... In recent years, ozone depletion has become a significant concern. Because, rising UV-B radiation can damage DNA, RNA, proteins, lipids, cell membranes, and the photosynthetic machine and affect various biological pathways, which can be harmful for organisms (Razeghi and Kianianmomeni 2019;Fernández et al. 2020). ...
Long non-coding RNAs (lncRNAs) are identified as important regulatory molecules related to diverse biological processes. In recent years, benefiting from the rapid development of high-throughput sequencing technology, RNA-seq, and analysis methods, more lncRNAs have been identified and discovered in various plant and algal species. However, so far, only limited studies related to algal lncRNAs are available. Volvox carteri f. nagariensis is the best multicellular model organism to study in developmental and evolutionary biology; therefore, studying and increasing information about this species is important. This study identified lncRNAs in the multicellular green algae Volvox carteri and 1457 lncRNAs were reported, using RNA-seq data and with the help of bioinformatics tools and software. This study investigated the effect of low-dose UV-B radiation on changes in the expression profile of lncRNAs in gonidial and somatic cells. The differential expression of lncRNAs was analyzed between the treatment (UV-B) and the control (WL) groups in gonidial and somatic cells. A total of 37 and 26 lncRNAs with significant differential expression in gonidial and somatic cells, respectively, were reported. Co-expression analysis between the lncRNAs and their neighbor protein-coding genes (in the interval of ± 10 Kb) was accomplished. In gonidial cells, 184 genes with a positive correlation and 13 genes with a negative correlation (greater than 0.95), and in somatic cells, 174 genes with a positive correlation, and 18 genes with a negative correlation were detected. Functional analysis of neighboring coding genes was also performed based on gene ontology. The results of the current work may help gain deeper insight into the regulation of gene expression in the studied model organism, Volvox carteri.
... Variations in UVR8 expression were also reported in UV-B-treated fruit skin and apple callus (Mao et al. 2015). On the other hand, no differences in the expression level of UVR8 after UV-B irradiation were found in somatic and reproductive cells from the multicellular algae Volvox carteri (Razeghi and Kianianmomeni 2019). Differences observed in UVR8 expression in the literature could result from the different UV-B intensities used in the experiments and tissues analyzed. ...
Low UV-B fluence is a signaling stimulus that regulates various physiological processes and induces photomorphogenic responses in plants. The specific UV-B receptor UVR8 is a key component in these processes. Although UVR8 sequence is conserved, few homologs have been cloned and reported to be functional. Here we show the cloning and functional analysis of Zea mays UVR8 (ZmUVR8). ZmUVR8 presents 73% of identity with AtUVR8, maintaining the key tryptophan responsible of UV-B perception. ZmUVR8 also contains the VP domain, involved in the interaction with the proteins CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) and REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 (RUP1). Whereas UVR8 was expressed in non-irradiated Arabidopsis and maize leaves, after 2 h of UV-B irradiation, its expression was reduced. The expression of chalcone synthase (CHS), involved in flavonoid biosynthesis and regulated by UVR8, was increased in irradiated Arabidopsis and maize leaves. Arabidopsis uvr8-1 null mutant was complemented with ZmUVR8 driven by the CaMV-35S promoter and fused to eGFP. ZmUVR8-eGFP fusion was mainly localized in nuclei of transgenic lines, irrespective of UV-B treatments. UV-B suppressed hypocotyl elongation in wild type (WT) Arabidopsis plants, whereas in uvr8-1 hypocotyl growth was observed. However, hypocotyl elongation was reduced in UV-B irradiated transgenic lines complemented with ZmUVR8. Moreover, CHS and transcription factor HY5 (ELONGATED HYPOCOTYL 5) expression were also restored in these plants. These results confirm that ZmUVR8 is similar enough to AtUVR8 to restore UV-B perception and signaling in Arabidopsis mutant uvr8-1, thus being a functional UV-B photoreceptor. That reinforce the importance of UVR8 as a functional UV-B-responsive regulator in land plants.
... This multicellular green alga seems to have a photoreceptor which can play a role in UV-B response. 19 According to previous studies, reproductive and somatic cells demonstrate a differentially expressed gene (DEG) pattern from various functional classes. 20,21 Transcriptome profiling is utilized as one of the most frequent approaches for investigating the changes in gene expression at the molecular level. ...
... The sequence of VcUVR8-V1 gene in V. carteri was used to investigate UV-B photoreceptor. 19 In addition, a set of candidate genes was selected from different gene databases such as NCBI, Phytozome (phytozome.jgi.doe.gov) and Ensembl (plants. ensembl.org) ...
There is a scarcity of research reports on the effect of ultraviolet (UV)-B radiation on genome-wide transcriptional regulation in the multicellular green microalga including Volvox carteri (V. carteri). This microalga possesses only two cell types including mortal and motile somatic cells, as well as immortal and immotile reproductive cells. Therefore, the present study evaluated the effect of low-dose UV-B radiation on the cell-type-specific gene expression pattern of reproductive and somatic cells in an asexual life cycle of V. carteri using RNA sequence method. To this end, the separated reproductive and somatic cells were treated for 1 hour at an intensity of 0.056 mW/cm⁻² UV-B radiation. Then, a transcriptome analysis was conducted between the UV-B and white light treated groups in either of the cell types. Based on differential gene expression analyses, no differentially expressed genes were found in reproductive cells under the treatment as compared to the control group. This type of cell maintained its steady state. However, treating the somatic cells with UV-B radiation led to at least 126 differentially expressed genes compared to the untreated control group. In addition, the results of a direct comparison demonstrated a restricted and wide response to UV-B radiation in somatic cells as compared to reproductive cells. Based on the results, UV-B radiation could be involved in cell-type-specific regulation of biological pathways.
Photosynthesis, the fundamental process using light energy to convert CO 2 to organic matter, is vital for life on Earth. It relies on capturing light through light-harvesting complexes in evolutionarily well-conserved photosystems (PS) I and II and on the conversion of light energy into chemical energy. Composition and organization of both photosystem core complexes are well conserved across evolution. PSII is particularly sensitive to photodamage but benefits from a large diversity of photoprotective mechanisms, finely tuned for the specific 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 photosystems capture light energy whereas others dissipate excess energy that cannot be harnessed for photosynthesis. This process mainly occurs through non photochemical quenching (NPQ). In this work, we focus on the LHL4 protein, which is a LHC-like protein induced by UV-B and blue light photoreceptor 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 it 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.
Main Conclusion
Light, hormones and their interaction regulate different aspects of development in non-flowering plants. They might have played a role in the evolution of different plant groups by conferring specific adaptive evolutionary changes.
Abstract
Plants are sessile organisms. Unlike animals, they lack the opportunity to abandon their habitat in unfavorable conditions. They respond to different environmental cues and adapt accordingly to control their growth and developmental pattern. While phytohormones are known to be internal regulators of plant development, light is a major environmental signal that shapes plant processes. It is plausible that light-hormone crosstalk might have played an important role in plant evolution. But how the crosstalk between light and phytohormone signaling pathways might have shaped the plant evolution is unclear. One of the possible reasons is that flowering plants have been studied extensively in context of plant development, which cannot serve the purpose of evolutionary comparisons. In order to elucidate the role of light, hormone and their crosstalk in the evolutionary adaptation in plant kingdom, one needs to understand various light- and hormone-mediated processes in diverse non-flowering plants. This review is an attempt to outline major light- and phytohormone-mediated responses in non-flowering plant groups such as algae, bryophytes, pteridophytes and gymnosperms.
