Publications by authors named "Bryan Ruiz"

5 Publications

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Rhizobia: highways to NO.

Biochem Soc Trans 2021 Feb;49(1):495-505

Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRA, CNRS, INSA, 31326 Castanet-Tolosan, France.

The interaction between rhizobia and their legume host plants conduces to the formation of specialized root organs called nodules where rhizobia differentiate into bacteroids which fix atmospheric nitrogen to the benefit of the plant. This beneficial symbiosis is of importance in the context of sustainable agriculture as legumes do not require the addition of nitrogen fertilizer to grow. Interestingly, nitric oxide (NO) has been detected at various steps of the rhizobium-legume symbiosis where it has been shown to play multifaceted roles. Both bacterial and plant partners are involved in NO synthesis in nodules. To better understand the role of NO, and in particular the role of bacterial NO, at all steps of rhizobia-legumes interaction, the enzymatic sources of NO have to be elucidated. In this review, we discuss different enzymatic reactions by which rhizobia may potentially produce NO. We argue that there is most probably no NO synthase activity in rhizobia, and that instead the NO2- reductase nirK, which is part of the denitrification pathway, is the main bacterial source of NO. The nitrate assimilation pathway might contribute to NO production but only when denitrification is active. The different approaches to measure NO in rhizobia are also addressed.
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http://dx.doi.org/10.1042/BST20200989DOI Listing
February 2021

Epithelial Migration and Non-adhesive Periderm Are Required for Digit Separation during Mammalian Development.

Dev Cell 2020 03 27;52(6):764-778.e4. Epub 2020 Feb 27.

Department of Biological Chemistry, School of Medicine, University of California, Irvine, Irvine, CA, USA; Department of Medicine, School of Medicine, University of California, Irvine, Irvine, CA, USA. Electronic address:

The fusion of digits or toes, syndactyly, can be part of complex syndromes, including van der Woude syndrome. A subset of van der Woude cases is caused by dominant-negative mutations in the epithelial transcription factor Grainyhead like-3 (GRHL3), and Grhl3mice have soft-tissue syndactyly. Although impaired interdigital cell death of mesenchymal cells causes syndactyly in multiple genetic mutants, Grhl3 embryos had normal interdigital cell death, suggesting alternative mechanisms for syndactyly. We found that in digit separation, the overlying epidermis forms a migrating interdigital epithelial tongue (IET) when the epithelium invaginates to separate the digits. Normally, the non-adhesive surface periderm allows the IET to bifurcate as the digits separate. In contrast, in Grhl3 embryos, the IET moves normally between the digits but fails to bifurcate because of abnormal adhesion of the periderm. Our study identifies epidermal developmental processes required for digit separation.
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http://dx.doi.org/10.1016/j.devcel.2020.01.032DOI Listing
March 2020

The Nitrate Assimilatory Pathway in : Contribution to NO Production.

Front Microbiol 2019 3;10:1526. Epub 2019 Jul 3.

Laboratoire des Interactions Plantes-Microorganismes (LIPM), INRA, CNRS, INSA, Université de Toulouse, Castanet-Tolosan, France.

The interaction between rhizobia and their legume host plants culminates in the formation of specialized root organs called nodules in which differentiated endosymbiotic bacteria (bacteroids) fix atmospheric nitrogen to the benefit of the plant. Interestingly, nitric oxide (NO) has been detected at various steps of the rhizobium-legume symbiosis where it has been shown to play multifaceted roles. It is recognized that both bacterial and plant partners of the - symbiosis are involved in NO synthesis in nodules. can also produce NO from nitrate when living as free cells in the soil. does not possess any NO synthase gene in its genome. Instead, the denitrification pathway is often described as the main driver of NO production with nitrate as substrate. This pathway includes the periplasmic nitrate reductase (Nap) which reduces nitrate into nitrite, and the nitrite reductase (Nir) which reduces nitrite into NO. However, additional genes encoding putative nitrate and nitrite reductases (called and , respectively) have been identified in the genome. Here we examined the conditions where these genes are expressed, investigated their involvement in nitrate assimilation and NO synthesis in culture and their potential role . We found that and are expressed under aerobic conditions in absence of ammonium in the medium and most likely belong to the nitrate assimilatory pathway. Even though these genes are clearly expressed in the fixation zone of legume root nodule, they do not play a crucial role in symbiosis. Our results support the hypothesis that in , denitrification remains the main enzymatic way to produce NO while the assimilatory pathway involving NarB and NirB participates indirectly to NO synthesis by cooperating with the denitrification pathway.
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http://dx.doi.org/10.3389/fmicb.2019.01526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6616083PMC
July 2019

Cytoplasmic and Nuclear TAZ Exert Distinct Functions in Regulating Primed Pluripotency.

Stem Cell Reports 2017 09 24;9(3):732-741. Epub 2017 Aug 24.

Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Electronic address:

Mouse epiblast stem cells (mEpiSCs) and human embryonic stem cells (hESCs) are primed pluripotent stem cells whose self-renewal can be maintained through cytoplasmic stabilization and retention of β-catenin. The underlying mechanism, however, remains largely unknown. Here, we show that cytoplasmic β-catenin interacts with and retains TAZ, a Hippo pathway effector, in the cytoplasm. Cytoplasmic retention of TAZ promotes mEpiSC self-renewal in the absence of nuclear β-catenin, whereas nuclear translocation of TAZ induces mEpiSC differentiation. TAZ is dispensable for naive mouse embryonic stem cell (mESC) self-renewal but required for the proper conversion of mESCs to mEpiSCs. The self-renewal of hESCs, like that of mEpiSCs, can also be maintained through the cytoplasmic retention of β-catenin and TAZ. Our study indicates that how TAZ regulates cell fate depends on not only the cell type but also its subcellular localization.
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http://dx.doi.org/10.1016/j.stemcr.2017.07.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5599246PMC
September 2017

Klf2 and Tfcp2l1, Two Wnt/β-Catenin Targets, Act Synergistically to Induce and Maintain Naive Pluripotency.

Stem Cell Reports 2015 Sep 28;5(3):314-22. Epub 2015 Aug 28.

Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, University of Southern California, Los Angeles, CA 90033, USA. Electronic address:

Activation of Wnt/β-catenin signaling can induce both self-renewal and differentiation in naive pluripotent embryonic stem cells (ESCs). To gain insights into the mechanism by which Wnt/β-catenin regulates ESC fate, we screened and characterized its downstream targets. Here, we show that the self-renewal-promoting effect of Wnt/β-catenin signaling is mainly mediated by two of its downstream targets, Klf2 and Tfcp2l1. Forced expression of Klf2 and Tfcp2l1 can not only induce reprogramming of primed state pluripotency into naive state ESCs, but also is sufficient to maintain the naive pluripotent state of ESCs. Conversely, downregulation of Klf2 and Tfcp2l1 impairs ESC self-renewal mediated by Wnt/β-catenin signaling. Our study therefore establishes the pivotal role of Klf2 and Tfcp2l1 in mediating ESC self-renewal promoted by Wnt/β-catenin signaling.
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http://dx.doi.org/10.1016/j.stemcr.2015.07.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4618593PMC
September 2015