Artículos (Bioquímica Vegetal y Biología Molecular)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10824

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2-Cys peroxiredoxins contribute to thylakoid lipid unsaturation by affecting ω-3 fatty acid desaturase 8
(AMER SOC PLANT BIOLOGISTS; OXFORD UNIV PRESS INC, 2024-02-22) Hernández Jiménez, María Luisa; Jiménez López, Julia; Cejudo Fernández, Francisco Javier; Pérez Ruiz, Juan Manuel; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; National Institutes of Health. United States; USDA National Institute of Food and Agriculture
Fatty acid unsaturation levels affect chloroplast function and plant acclimation to environmental cues. However, the regulatory mechanism(s) controlling fatty acid unsaturation in thylakoid lipids is poorly understood. Here, we have investigated the connection between chloroplast redox homeostasis and lipid metabolism by focusing on 2-Cys peroxiredoxins (Prxs), which play a central role in balancing the redox state within the organelle. The chloroplast redox network relies on NADPH-dependent thioredoxin reductase C (NTRC), which controls the redox balance of 2-Cys Prxs to maintain the reductive activity of redox-regulated enzymes. Our results show that Arabidopsis (Arabidopsis thaliana) mutants deficient in 2-Cys Prxs contain decreased levels of trienoic fatty acids, mainly in chloroplast lipids, indicating that these enzymes contribute to thylakoid membrane lipids unsaturation. This function of 2-Cys Prxs is independent of NTRC, the main reductant of these enzymes, hence 2-Cys Prxs operates beyond the classic chloroplast regulatory redox system. Moreover, the effect of 2-Cys Prxs on lipid metabolism is primarily exerted through the prokaryotic pathway of glycerolipid biosynthesis and fatty acid desaturase 8 (FAD8). While 2-Cys Prxs and FAD8 interact in leaf membranes as components of a large protein complex, the levels of FAD8 were markedly decreased when FAD8 is overexpressed in 2-Cys Prxs- deficient mutant backgrounds. These findings reveal a function for 2-Cys Prxs, possibly acting as a scaffold protein, affecting the unsaturation degree of chloroplast membranes.
A common signalosome for programmed cell death in humans and plants
(Nature Publishing Group, 2014) Martínez Fábregas, Jonathan; Díaz Moreno, Irene; González Arzola, Katiuska; Díaz Quintana, Antonio Jesús; Rosa Acosta, Miguel Ángel de la; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
A comparative analysis of the NADPH thioredoxin reductase C-2-Cys peroxiredoxin system from plants and Cyanobacteria
(American Society of Plant Biologists, 2011) Pascual, María Belén; Mata Cabana, Alejandro; Florencio Bellido, Francisco Javier; Lindahl, Anna Marika; Cejudo Fernández, Francisco Javier; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
Redox regulation based on disulfide-dithiol conversion catalyzed by thioredoxins is an important component of chloroplast function. The reducing power is provided by ferredoxin reduced by the photosynthetic electron transport chain. In addition, chloroplasts are equipped with a peculiar NADPH-dependent thioredoxin reductase, termed NTRC, with a joint thioredoxin domain at the carboxyl terminus. Because NADPH can be produced by the oxidative pentose phosphate pathway during the night, NTRC is important to maintain the chloroplast redox homeostasis under light limitation. NTRC is exclusive for photosynthetic organisms such as plants, algae, and some, but not all, cyanobacteria. Phylogenetic analysis suggests that chloroplast NTRC originated from an ancestral cyanobacterial enzyme. While the biochemical properties of plant NTRC are well documented, little is known about the cyanobacterial enzyme. With the aim of comparing cyanobacterial and plant NTRCs, we have expressed the full-length enzyme from the cyanobacterium Anabaena species PCC 7120 as well as site-directed mutant variants and truncated polypeptides containing the NTR or the thioredoxin domains of the protein. Immunological and kinetic analysis showed a high similarity between NTRCs from plants and cyanobacteria. Both enzymes efficiently reduced 2-Cys peroxiredoxins from plants and from Anabaena but not from the cyanobacterium Synechocystis. Arabidopsis (Arabidopsis thaliana) NTRC knockout plants were transformed with the Anabaena NTRC gene. Despite a lower content of NTRC than in wild-type plants, the transgenic plants showed significant recovery of growth and pigmentation. Therefore, the Anabaena enzyme fulfills functions of the plant enzyme in vivo, further emphasizing the similarity between cyanobacterial and plant NTRCs.
A complex and dynamic redox network regulates oxygen reduction at photosystem I in Arabidopsis
(Oxford Academic Press, 2024-09-26) Hani, Umama; Naranjo Río-Miranda, Belén; Shimakawa, Ginga; Espinasse, Christophe; Vanacker, Helene; Setif, Pierre; Rintamaki, Eevi; Issakidis-Bourguet, Emmanuelle; Krieger-Liszkay, Anja; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ecole Universitaire de Recherche de Sciences des Plantes de Paris-Saclay (SPS-GSR); Agence Nationale de la Recherche. France; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España
Thiol-dependent redox regulation of enzyme activities plays a central role in regulating photosynthesis. Besides the regulation of metabolic pathways, alternative electron transport is subjected to thiol-dependent regulation. We investigated the regulation of O2 reduction at photosystem I. The level of O2 reduction in leaves and isolated thylakoid membranes depends on the photoperiod in which plants are grown. We used a set of Arabidopsis (Arabidopsis thaliana) mutant plants affected in the stromal, membrane, and lumenal thiol network to study the redox protein partners involved in regulating O2 reduction. Light-dependent O2 reduction was determined in leaves and thylakoids of plants grown in short-day and long-day conditions using a spin-trapping electron paramagnetic resonance assay. In wild-type samples from short-day conditions, reactive oxygen species generation was double that of samples from long-day conditions, while this difference was abolished in several redoxin mutants. An in vitro reconstitution assay showed that thioredoxin m, NADPH-thioredoxin reductase C, and NADPH are required for high O2-reduction levels in thylakoids from plants grown in long-day conditions. Using isolated photosystem I, we also showed that reduction of a photosystem I protein is responsible for the increase in O2 reduction. Furthermore, differences in the membrane localization of m-type thioredoxins and 2-Cys peroxiredoxin were detected between thylakoids of short-day and long-day plants. Overall, we propose a model of redox regulation of O2 reduction according to the reduction power of the stroma and the ability of different thiol-containing proteins to form a network of redox interactions.
A contribution to the study of plant development evolution based on gene co-expression networks
(Frontiers media, 2013) Romero Campero, Francisco José; Lucas Reina, Eva; Said, Fátima E.; Romero Rodríguez, José María; Valverde Albacete, Federico; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Universidad de Sevilla. Departamento de Ciencias de la Computación e Inteligencia Artificial; Ministerio de Economía y Competitividad (MINECO). España
Phototrophic eukaryotes are among the most successful organisms on Earth due to their unparalleled efficiency at capturing light energy and fixing carbon dioxide to produce organic molecules. A conserved and efficient network of light-dependent regulatory modules could be at the bases of this success. This regulatory system conferred early advantages to phototrophic eukaryotes that allowed for specialization, complex developmental processes and modern plant characteristics. We have studied light-dependent gene regulatory modules from algae to plants employing integrative-omics approaches based on gene co-expression networks. Our study reveals some remarkably conserved ways in which eukaryotic phototrophs deal with day length and light signaling. Here we describe how a family of Arabidopsis transcription factors involved in photoperiod response has evolved from a single algal gene according to the innovation, amplification and divergence theory of gene evolution by duplication. These modifications of the gene co-expression networks from the ancient unicellular green algae Chlamydomonas reinhardtii to the modern brassica Arabidopsis thaliana may hint on the evolution and specialization of plants and other organisms.
A core of three amino acids at the carboxyl-terminal region of glutamine synthetase defines its regulation in cyanobacteria
(Wiley, 2015) Saelices Gómez, Lorena; Robles Rengel, Rocio; Florencio Bellido, Francisco Javier; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Economía y Competitividad (MINECO). España; Junta de Andalucía
Glutamine synthetase (GS) type I is a key enzyme in nitrogen metabolism, and its activity is finely controlled by cellular carbon/nitrogen balance. In cyanobacteria, a reversible process that involves protein-protein interaction with two proteins, the inactivating factors IF7 and IF17, regulates GS. Previously, we showed that three arginine residues of IFs are critical for binding and inhibition of GS. In this work, taking advantage of the specificity of GS/IFs interaction in the model cyanobacteria Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120, we have constructed a different chimeric GSs from these two cyanobacteria. Analysis of these proteins, together with a site-directed mutagenesis approach, indicates that a core of three residues (E419, N456 and R459) is essential for the inactivation process. The three residues belong to the last 56 amino acids of the C-terminus of SynechocystisGS. A protein-protein docking modeling of SynechocystisGS in complex with IF7 supports the role of the identified core for GS/IF interaction.
A functional RNase P protein subunit of bacterial origin in some eukaryotes
(Springer, 2011) Lai, Lien B.; Bernal Bayard, Pilar; Mohannath, Gireesha; Lai, Stella M.; Gopalan, Venkat; Vioque Peña, Agustín; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
RNase P catalyzes 5′-maturation of tRNAs. While bacterial RNase P comprises an RNA catalyst and a protein cofactor, the eukaryotic (nuclear) variant contains an RNA and up to ten proteins, all unrelated to the bacterial protein. Unexpectedly, a nuclear-encoded bacterial RNase P protein (RPP) homolog is found in several prasinophyte algae including Ostreococcus tauri. We demonstrate that recombinant O. tauri RPP can functionally reconstitute with bacterial RNase P RNAs (RPRs) but not with O. tauri organellar RPRs, despite the latter’s presumed bacterial origins. We also show that O. tauri PRORP, a homolog of Arabidopsis PRORP-1, displays tRNA 5′-processing activity in vitro. We discuss the implications of the striking diversity of RNase P in O. tauri, the smallest known free-living eukaryote.
A gene cluster involved in metal homeostasis in the cyanobacterium Synechocystis sp. strain PCC 6803
(American Society for Microbiology, 2000) García Domínguez, Mario; López Maury, Luis; Florencio Bellido, Francisco Javier; Reyes Rosa, José Carlos; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Educación y Cultura (MEC). España; Junta de Andalucía
A gene cluster composed of nine open reading frames (ORFs) involved in Ni2+, Co2+, and Zn2+ sensing and tolerance in the cyanobacterium Synechocystis sp. Strain PCC 6803 has been identified. The cluster includes an Ni2+ response operon and a Co2+ response system, as well as a Zn2+ response system previously described. Expression of the Ni2+ response operon (nrs) was induced in the presence of Ni2+ and Co2+. Reduced Ni2+ tolerance was observed following disruption of two ORFs of the operon (nrsA and nrsD). We also show that the nrsD gene encodes a putative Ni2+ permease whose carboxy-terminal region is a metal binding domain. The Co2+ response system is composed of two divergently transcribed genes, corR and corT, mutants of which showed decreased Co2+ tolerance. Additionally, corR mutants showed an absence of Co2+-dependent induction of corT, indicating that CorR is a transcriptional activator of corT. To our knowledge, CorR is the first Co2+-sensing transcription factor described. Our data suggest that this region of the Synechocystis sp. strain PCC 6803 genome is involved in sensing and homeostasis of Ni2+, Co2+, and Zn2+.
A gibberellin-induced nuclease is localized in the nucleus of wheat aleurone cells undergoing programmed cell death
(The American Society for Biochemistry and Molecular Biology, 2003) Domínguez del Toro, Fernando; Moreno Onorato, Francisco Javier; Cejudo Fernández, Francisco Javier; Universidad de Sevilla. Departamento de Biología Celular; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
The aleurone layer of cereal grains undergoes a gibberellin-regulated process of programmed cell death (PCD) following germination. We have applied a combination of ultrastructural and biochemical approaches to analyze aleurone PCD in intact wheat grains. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay revealed that PCD was initiated in aleurone cells proximal to the embryo and then extended to distal cells. DNA fragmentation and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling analysis revealed PCD of aleurone cells in maize grains, although the process was delayed as compared with wheat. Aleurone cells undergoing PCD showed a rapid vacuolation with high lytic activity in the cytoplasm, whereas the nucleus, which adopted an irregular shape, appeared essentially intact and showed symptoms of degradation at the end of the process. A nuclease activity was identified localized in the nucleus of aleurone cells undergoing PCD, just prior to the appearance of DNA laddering. This nuclease was induced by gibberellic acid treatment and was not detected when gibberellin synthesis was inhibited or in gibberellic acid-insensitive mutants. This nuclease was activated by Ca2 and Mg2 , strongly inhibited by Zn2 , and showed optimum activity at neutral pH, resembling nucleases involved in apoptosis of animal cells.
A major facilitator superfamily protein, HepP, is involved in formation of the heterocyst envelope polysaccharide in the cyanobacterium Anabaena sp. Strain PCC 7120
(American Society for Microbiology, 2012) López Igual, Rocío; Lechno Yossef, Sigal; Fang, Qing; Herrero Moreno, Antonia; Flores García, Enrique; Wolk, C. Peter; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Ciencia y Tecnología (MCYT). España
Some filamentous cyanobacteria such as Anabaena sp. strain PCC 7120 produce cells, termed heterocysts, specialized in nitrogen fixation. Heterocysts bear a thick envelope containing an inner layer of glycolipids and an outer layer of polysaccharide that restrict the diffusion of air(including O2) into the heterocyst. Anabaena sp. mutants impaired in production of either of those layers show a Fox- phenotype (requiring fixed nitrogen for growth under oxic conditions). We have characterized a set of transposon-induced Fox- mutants in which transposon Tn5-1063 was inserted into the Anabaena sp. chromosome open reading frame all1711 which encodes a predicted membrane protein that belongs to the major facilitator superfamily (MFS). These mutants showed higher nitrogenase activities under anoxic than under oxic conditions and altered sucrose uptake. Electron microscopy and alcian blue staining showed a lack of the heterocyst envelope polysaccharide (Hep) layer. Northern blot and primer extension analyses showed that, in a manner dependent on the nitrogen-control transcription factor NtcA, all1711 was strongly induced after nitrogen step-down. Confocal microscopy of an Anabaena sp. strain producing an All1711-green fluorescent protein (All1711-GFP) fusion protein showed induction in all cells of the filament but at higher levels in differentiating heterocysts. All1711-GFP was located in the periphery of the cells, consistent with All1711 being a cytoplasmic membrane protein. Expression of all1711 from the PglnA promoter in a multicopy plasmid led to production of a presumptive exopolysaccharide by vegetative cells. These results suggest that All1711, which we denote HepP, is involved in transport of glycoside(s), with a specific physiological role in production of Hep.
A metabolic strategy to enhance long-term survival by Phx1 through stationary phase-specific pyruvate decarboxylases in fission yeast
(Impact Journals, 2014) Kim, Jiyoon; Kim, Eunjung; López Maury, Luis; Bähler, Jürg Ürg; Roe, Junghye; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
In the fission yeast Schizosaccharomyces pombe, the stationary phase‐specific transcription factor Phx1 contributes to long‐term survival, stress tolerance, and meiosis. We identified Phx1‐dependent genes through transcriptome analysis, and further analyzed those related with carbohydrate and thiamine metabolism, whose expression decreased in Δphx1. Consistent with mRNA changes, the level of thiamine pyrophosphate (TPP) and TPP‐utilizing pyruvate decarboxylase activity that converts pyruvate to acetaldehyde were also reduced in the mutant. Therefore, Phx1 appears to shift metabolic flux by diverting pyruvate from the TCA cycle and respiration to ethanol fermentation. Among the four predicted genes for pyruvate decarboxylase, only the Phx1‐dependent genes (pdc201+ and pdc202+) contributed to longterm survival as judged by mutation and overexpression studies. These findings indicate that the Phx1‐mediated long‐term survival is achieved primarily through increasing the synthesis and activity of pyruvate decarboxylase. Consistent with this hypothesis, we observed that Phx1 curtailed respiration when cells entered stationary phase. Introduction of Δphx1 mutation compromised the long‐lived phenotypes of Δpka1 and Δsck2 mutants that are devoid of pro‐aging kinases of nutrient‐signalling pathways, and of the Δpyp1 mutant with constitutively activated stress‐responsive kinase Sty1. Therefore, achievement of long‐term viability through both nutrient limitation and anti‐stress response appears to be dependent on Phx1
A mutant lacking the glutamine synthetase gene (glnA) is impaired in the regulation of the nitrate assimilation system in the cyanobacterium Synechocystis sp. strain PCC 6803
(American Society for Microbiology, 1994) Reyes, José C.; Florencio Bellido, Francisco Javier; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Dirección General de Investigación Científica y Técnica (DGICYT). España
The existence in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 of two genes (glnA and glnN) coding for glutamine synthetase (GS) has been recently reported (J.C. Reyes and F.J. Florencio, J. Bacteriol. 176:1260-1267, 1994). In the current work, the regulation of the nitrate assimilation system was studied with a glnA-disrupted Synechocystis mutant (strain SJCR3) in which the only GS activity is that corresponding to the glnN product. This mutant was unable to grow in ammonium-containing medium because of its very low levels of GS activity. In the SJCR3 strain, nitrate and nitrite reductases were not repressed by ammonium, and short-term ammonium-promoted inhibition of nitrate uptake was impaired. In Synechocystis sp. strain PCC 6803, nitrate seems to act as a true inducer of its assimilation system, in a way similar to that proposed for the dinitrogen-fixing cyanobacteria. A spontaneous derivative strain from SJCR3 (SJCR3.1), was able to grow in ammonium-containing medium and exhibited a fourfold-higher level of GS activity than but the same amount of glnN transcript as its parental strain (SJCR3). Taken together, these finding suggest that SJCR3.1 is a mutant affected in the posttranscriptional regulation of the GS encoded by glnN. This strain recovered regulation by ammonium of nitrate assimilation. SJCR3 cells were completely depleted of intracellular glutamine shortly after addition of ammonium to cells growing with nitrate, while SJCR3.1 cells maintained glutamine levels similar to that reached in the wild-type Synechocystis sp. strain PCC 6803. Our results indicate that metabolic signals that control the nitrate assimilation system in Synechocystis sp. strain PCC 6803 require ammonium metabolism through GS.
A new member of the thioredoxin reductase family from early uxygenic photosynthetic organisms
(Oxford University Press, 2017) Buey, Rubén M.; Galindo Trigo, Sergio; López Maury, Luis; Velázquez Campoy, Adrián; Revuelta, José Luis; Florencio Bellido, Francisco Javier; Pereda, José M. de; Schürmann, Peter; Buchanan, Bob B.; Balsera, Monica; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
Thioredoxins (Trxs) are key components of the redox system that regulates the activity of a spectrum of target proteins through dithiol-disulfide exchange reactions. Trxs are reduced by members of the Trx reductase (TR) family (Jacquot et al., 2009). NADP-dependent thioredoxin reductases (NTRs), the most common type, belong to the family of dimeric pyridine nucleotide disulfide oxidoreductase flavoproteins that use NADPH as the source of reducing equivalents. In oxyphotosynthetic organisms, in particular, NTRs coexist with the ferredoxin/thioredoxin system (FTS), composed of ferredoxin (Fdx), ferredoxin:thioredoxin reductase (FTR), and a Trx. FTRs convert the electron signal obtained from photoreduced Fdx to a thiol signal via a 4Fe-4S center and a redox-active disulfide catalytic center. FTR, in turn, reduces Trx.
A new treatment for sarcoma extracted from combination of miRNA deregulation and gene association rules
(Springer Nature, 2023) García Heredia, José Manuel; Perez, Marco; Verdugo Sivianes, Eva María; Martínez Ballesteros, María del Mar; Ortega Campos, Sara M.; Carnero, Amancio; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Universidad de Sevilla. Departamento de Lenguajes y Sistemas Informáticos; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE); Centro de Investigación Biomédica en Red (CIBER); Junta de Andalucía; Asociación Española contra el Cáncer
A New Type of Asymmetrically Acting β-Carotene Ketolase Is Required for the Synthesis of Echinenone in the Cyanobacterium Synechocystis sp. PCC 6803
(Elsevier, 1997) Fernández González, Blanca María; Sandmann, Gerhard; Vioque Peña, Agustín; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
We have isolated, based on the knowledge of the complete genomic sequence of the cyanobacterium Synechocystis sp. PCC 6803, an open reading frame (slr0088) similar to known bacterial carotene desaturases and have analyzed the function of the encoded protein. Surprisingly, this protein has no detectable desaturase activity with phytoene, hydroxyneurosporene, or ζ-carotene as substrates, but is rather a β-carotene ketolase that acts asymmetrically introducing a keto group on only one of the two β-ionone rings of β-carotene to generate echinenone. This is in contrast to the so far characterized β-carotene ketolases that act symmetrically, producing the di-keto carotenoid canthaxanthin from β-carotene without significant accumulation of echinenone. We have designated this new gene crtO The function of the crtO gene product has been demonstrated by 1) the biosynthesis of echinenone when the crtO gene is expressed in an Escherichia coli strain able to accumulate β-carotene, 2) the in vitro biosynthesis of echinenone from β-carotene with cell free extracts from E. coli cells that express the crtO gene, and 3) the absence of echinenone in a Synechocystis strain in which the crtO gene has been insertionally inactivated. The primary structure of the Synechocystis asymmetric ketolase bears no similarity with the known β-carotene ketolases. crtO is not required for normal growth under standard or high light conditions, neither is the photosynthetic activity of the crtO-deficient strain affected.
A new type of glutamine synthetase in cyanobacteria: The protein encoded by the glnN gene supports nitrogen assimilation in Synechocystis sp. strain PCC 6803
(American Society for Microbiology, 1994) Reyes Rosa, José Carlos; Florencio Bellido, Francisco Javier; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Dirección General de Investigación Científica y Técnica (DGICYT). España
A new glutamine synthetase gene, glnN, which encodes a polypeptide of 724 amino acid residues (M(r), 79,416), has been identified in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803; this is the second gene that encodes a glutamine synthetase (GS) in this cyanobacterium. The functionality of this gene was evidenced by its ability to complement an Escherichia coli glnA mutant and to support Synechocystis growth in a strain whose glnA gene was inactivated by insertional mutagenesis. In this mutant (strain SJCR3), as well as in the wild-type strain, the second GS activity was subject to regulation by the nitrogen source, being strongly enhanced in nitrogen-free medium. Transcriptional fusion of a chloramphenicol acetyltransferase (cat) gene with the 5'-upstream region of glnN suggested that synthesis of the second Synechocystis GS is regulated at the transcriptional level. Furthermore, the level of glnN mRNA, a transcript of about 2,300 bases, was found to be strongly increased in nitrogen-free medium. The glnN product is similar to the GS subunits of Bacteroides fragilis and Butyrivibrio fibrisolvens, two obligate anaerobic bacteria whose GSs are markedly different from other prokaryotic and eukaryotic GSs. However, significant similarity is evident in the five regions which are homologous in all of the GSs so far described. The new GS gene was also found in other cyanobacteria but not in N2-fixing filamentous species.
A paradoxical mutant GATA factor
(American Society for Microbiology, 2004-04) Muro Pastor, María Isabel; Strauss, Joseph; Ramón, Ana; Scazzocchio, Claudio; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
The niiA (nitrite reductase) and niaD (nitrate reductase) genes of Aspergillus nidulans are subject to both induction by nitrate and repression by ammonium or glutamine. The intergenic region between these genes functions as a bidirectional promoter. In this region, nucleosomes are positioned under nonexpression conditions. On nitrate induction under derepressing conditions, total loss of positioning occurs. This is independent of transcription and of the NirA-speciflc transcription factor but absolutely dependent on the wide-domain GATA-binding AreA factor. We show here that a 3-amino-acid deletion in the basic carboxy-terminal sequence of the DNA-binding domain results in a protein with paradoxical properties. Its weak DNA binding is consistent with its loss-of-function phenotype on most nitrogen sources. However, it results in constitutive expression and superinducibility of niiA and niaD. Nucleosome loss of positioning is also constitutive. The mutation partially suppresses null mutations in the transcription factor NirA. AreA binds NirA in vitro, and the mutation does not affect this interaction. The in vivo methylation pattern of the promoter is drastically altered, suggesting the recruitment of one or more unknown transcription factors and/or a local distortion on the DNA double helix.
A plant proton-pumping inorganic pyrophosphatase functionally complements the vacuolar ATPase transport activity and confers bafilomycin resistance in yeast
(2011) Drake García, Rocío; Serrano Delgado, Aurelio; Pérez Castiñeira, José Román; Hernández López, Agustín; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
A protease-mediated mechanism regulates the cytochrome c6/plastocyanin switch in Synechocystis sp. PCC 6803
(NAS, 2021-01-25) García Cañas, Raquel María; Giner Lamia, Joaquín; Florencio Bellido, Francisco Javier; López Maury, Luis; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Economia, Industria y Competitividad (MINECO). España; Agencia Estatal de Investigación. España; Junta de Andalucía; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
After the Great Oxidation Event (GOE), iron availability was greatly decreased, and photosynthetic organisms evolved several alternative proteins and mechanisms. One of these proteins, plastocyanin, is a type I blue-copper protein that can replace cytochrome c6 as a soluble electron carrier between cytochrome b6f and photosystem I. In most cyanobacteria, expression of these two alternative proteins is regulated by copper availability, but the regulatory system remains unknown. Herein, we provide evidence that the regulatory system is composed of a BlaI/CopY-family transcription factor (PetR) and a BlaR-membrane protease (PetP). PetR represses petE (plastocyanin) expression and activates petJ (cytochrome c6), while PetP controls PetR levels in vivo. Using whole-cell extracts, we demonstrated that PetR degradation requires both PetP and copper. Transcriptomic analysis revealed that the PetRP system regulates only four genes (petE, petJ, slr0601, and slr0602), highlighting its specificity. Furthermore, the presence of petE and petRP in early branching cyanobacteria indicates that acquisition of these genes could represent an early adaptation to decreased iron bioavailability following the GOE.
A proxitome-RNA-capture approach reveals that processing bodies repress co-regulated hub genes
(American Society of Plant Biologists, 2023-11-16) Liu, Chen; Mentzelopoulou, Andriani; Hatzianestis, Ioannis H.; Tzagkarakis, Epameinondas; Skaltsogiannis, Vasileios; Ma, Xuemin; Michalopoulou, Vassiliki A.; Romero Campero, Francisco José; Romero Losada, Ana Belén; Sarris, Panagiotis F.; Marhavy, Peter; Bolter, Bettina; Kanterakis, Alexandros; Gutiérrez Beltrán, Emilio; Moschou, Panagiotis N.; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Universidad de Sevilla. Departamento de Ciencias de la Computación e Inteligencia Artificial; Carl Tryggers Stiftelse foer Vetenskaplig Forskning; Svenska Forskningsradet Formas; European Union (UE); Helge Ax:son Johnsons stiftelse; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
Cellular condensates are usually ribonucleoprotein assemblies with liquid- or solid-like properties. Because these subcellular structures lack a delineating membrane, determining their compositions is difficult. Here we describe a proximity-biotinylation approach for capturing the RNAs of the condensates known as processing bodies (PBs) in Arabidopsis (Arabidopsis thaliana). By combining this approach with RNA detection, in silico, and high-resolution imaging approaches, we studied PBs under normal conditions and heat stress. PBs showed a much more dynamic RNA composition than the total transcriptome. RNAs involved in cell wall development and regeneration, plant hormonal signaling, secondary metabolism/defense, and RNA metabolism were enriched in PBs. RNA-binding proteins and the liquidity of PBs modulated RNA recruitment, while RNAs were frequently recruited together with their encoded proteins. In PBs, RNAs follow distinct fates: in small liquid-like PBs, RNAs get degraded while in more solid-like larger ones, they are stored. PB properties can be regulated by the actin-polymerizing SCAR (suppressor of the cyclic AMP)-WAVE (WASP family verprolin homologous) complex. SCAR/WAVE modulates the shuttling of RNAs between PBs and the translational machinery, thereby adjusting ethylene signaling. In summary, we provide an approach to identify RNAs in condensates that allowed us to reveal a mechanism for regulating RNA fate.

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