Functional study of REBELOTE gene of Arabidopsis thaliana

Ponts entre les séquences d'acides nucléiques et les protéines, les ribosomes sont des composants essentiels des cellules vivantes. Composé d'ARN et de protéines ribosomiques, ils sont transportés, durant leurs biogenèses, du nucléole au cytoplasme, où ils traduisent les ARN messagers (ARNm) en protéines. Ces dernières années,  il a été montré que nombre de protéines ribosomiques étaient impliquées dans le développement d'Arabidopsis en intervenant sur la division et l'élongation cellulaire. L'impact d'un défaut de biogenèse des ribosomes sur le développement pourrait être expliqué par un effet dose, par une spécificité des ribosomes pour leur ARNm cibles ou par la multifonctionnalité de protéines ribosomiques. Les résultats obtenus montrent que REBELOTE (RBL), l'un des deux homologues chez Arabidopsis de la protéine NOC2p de levure, intervient probablement durant la biogenèse des ribosomes. Des mutations dans le gène RBL causent une gamme de phénotype de la létalité embryonnaire aux défauts de croissance (réduction de la taille de la plante, altération de la forme des feuilles...). Afin de mieux comprendre les processus contrôlés par RBL, la fonction ribosomique de RBL a été étudiée et ses interacteurs protéiques recherchés. Nous nous sommes ensuite focalisé sur les effets des mutations rbl sur la division et l'élongation cellulaire. Ce travail montre que les défauts observés aux niveaux moléculaire et cellulaire peuvent expliquer les retards de croissance des mutants rbl.Bridges between nucleic acids sequences and proteins, ribosomes are central components and the “auletes” of living cells.  Composed of ribosomal proteins and RNA, they move during their biogenesis from the nucleolus to the cytoplasm, where they translate RNA messengers into proteins. In the past years, some mutants of ribosomal-biogenesis-related proteins have shown the importance of these proteins during cell division and Arabidopsis development. The impact of ribosomal defects on development could be explained by dose effect (which could be important for cell fitness), specificity of ribosomes for some mRNA or multifunctional ribosomal proteins (Mary E. Byrne, 2009). Here I present our work on REBELOTE (RBL), one of the two Arabidopsis homologs of the yeast NOC2 protein, which act during the ribosomal 60S subunit biogenesis. Mutations in REBELOTE gene cause a range of phenotypes, from embryo lethality to growth defects (reduced plant size, altered leaf shape…). To have a better understanding of RBL-controlled processes, we first analyzed the ribosomal function of RBL, and searched for its protein partners. Our results shows that RBL act in two different nucleolar complexes supposed to regulate 60S ribosomal subunit biogenesis. Subsequently, we focused on the effects of rbl mutations on the cell division/elongation processes. Our work shows that defects observed at molecular and cellular levels could explain the slow down of cell divisions and growth delay in rbl mutants

Etude fonctionnelle du gène REBELOTE chez Arabidopsis thaliana

Ponts entre les séquences d'acides nucléiques et les protéines, les ribosomes sont des composants essentiels des cellules vivantes. Composé d'ARN et de protéines ribosomiques, ils sont transportés, durant leurs biogenèses, du nucléole au cytoplasme, où ils traduisent les ARN messagers (ARNm) en protéines. Ces dernières années, il a été montré que nombre de protéines ribosomiques étaient impliquées dans le développement d'Arabidopsis en intervenant sur la division et l'élongation cellulaire. L'impact d'un défaut de biogenèse des ribosomes sur le développement pourrait être expliqué par un effet dose, par une spécificité des ribosomes pour leur ARNm cibles ou par la multifonctionnalité de protéines ribosomiques. Les résultats obtenus montrent que REBELOTE (RBL), l'un des deux homologues chez Arabidopsis de la protéine NOC2p de levure, intervient probablement durant la biogenèse des ribosomes. Des mutations dans le gène RBL causent une gamme de phénotype de la létalité embryonnaire aux défauts de croissance (réduction de la taille de la plante, altération de la forme des feuilles...). Afin de mieux comprendre les processus contrôlés par RBL, la fonction ribosomique de RBL a été étudiée et ses interacteurs protéiques recherchés. Nous nous sommes ensuite focalisé sur les effets des mutations rbl sur la division et l'élongation cellulaire. Ce travail montre que les défauts observés aux niveaux moléculaire et cellulaire peuvent expliquer les retards de croissance des mutants rbl.Bridges between nucleic acids sequences and proteins, ribosomes are central components and the auletes of living cells. Composed of ribosomal proteins and RNA, they move during their biogenesis from the nucleolus to the cytoplasm, where they translate RNA messengers into proteins. In the past years, some mutants of ribosomal-biogenesis-related proteins have shown the importance of these proteins during cell division and Arabidopsis development. The impact of ribosomal defects on development could be explained by dose effect (which could be important for cell fitness), specificity of ribosomes for some mRNA or multifunctional ribosomal proteins (Mary E. Byrne, 2009). Here I present our work on REBELOTE (RBL), one of the two Arabidopsis homologs of the yeast NOC2 protein, which act during the ribosomal 60S subunit biogenesis. Mutations in REBELOTE gene cause a range of phenotypes, from embryo lethality to growth defects (reduced plant size, altered leaf shape ). To have a better understanding of RBL-controlled processes, we first analyzed the ribosomal function of RBL, and searched for its protein partners. Our results shows that RBL act in two different nucleolar complexes supposed to regulate 60S ribosomal subunit biogenesis. Subsequently, we focused on the effects of rbl mutations on the cell division/elongation processes. Our work shows that defects observed at molecular and cellular levels could explain the slow down of cell divisions and growth delay in rbl mutants.LYON-ENS Sciences (693872304) / SudocSudocFranceF

REBELOTE, a regulator of floral determinacy in Arabidopsis thaliana, interacts with both nucleolar and nucleoplasmic proteins

The nucleoplasm and nucleolus are the two main territories of the nucleus. While specific functions are associated with each of these territories (such as mRNA synthesis in the nucleoplasm and ribosomal rRNA synthesis in thenucleolus), some proteins are known to be located in both. Here, we investigated the molecular function of REBELOTE (RBL), an Arabidopsis thalianaprotein previously characterized as a regulator of floral meristem termination. We show that RBL displays a dual localization, in the nucleolus and nucleoplasm. Moreover, we used direct and global approaches to demonstrate that RBL interacts with nucleic acid-binding proteins. It binds to the NOC proteins SWA2, AtNOC2 and AtNOC3 in both the nucleolus and nucleoplasm, and also to OBE1 and VFP3/ENAP1. Taking into account the identities of these RBL interactors, we hypothesise that RBL acts both in ribosomal biogenesis and in the regulation of gene expression

REBELOTE, a regulator of floral determinacy in Arabidopsis thaliana, interacts with both nucleolar andnucleoplasmic proteins

International audienceThe nucleoplasm and nucleolus are the two main territories of the nucleus. While specific functions are associated with each of these territories (such as mRNA synthesis in the nucleoplasm and ribosomal rRNA synthesis in the nucleolus), some proteins are known to be located in both. Here, we investigated the molecular function of REBELOTE (RBL), an Arabidopsis thaliana protein previously characterized as a regulator of floral meristem termination. We show that RBL displays a dual localization, in the nucleolus and nucleoplasm. Moreover, we used direct and global approaches to demonstrate that RBL interacts with nucleic acid-binding proteins. It binds to the NOC proteins SWA2, AtNOC2 and AtNOC3 in both the nucleolus and nucleoplasm, and also to OBE1 and VFP3/ENAP1. Taking into account the identities of these RBL interactors, we hypothesize that RBL acts both in ribosomal biogenesis and in the regulation of gene expression

Plant science and agricultural productivity: Why are we hitting the yield ceiling?

International audienceTrends in conventional plant breeding and in biotechnology research are analyzed with a focus on production and productivity of individual organisms. Our growing understanding of the productive/adaptive potential of (crop) plants is a prerequisite to increasing this potential and also its expression under environmental constraints. This review concentrates on growth rate, ribosome activity, and photosynthetic rate to link these key cellular processes to plant productivity. Examples of how they may be integrated in heterosis, organ growth control, and responses to abiotic stresses are presented. The yield components in rice are presented as a model. The ultimate goal of research programs, that concentrate on yield and productivity and integrating the panoply of systems biology tools, is to achieve "low input, high output" agriculture, i.e. shifting from a conventional "productivist" agriculture to an efficient sustainable agriculture. This is of critical, strategic importance, because the extent to which we, both locally and globally, secure and manage the long-term productive potential of plant resources will determine the future of humanity