Regulation of plant stem cell quiescence by a brassinosteroid signaling module

Referred to by: Josep Vilarrasa-Blasi, Mary-Paz González-García, David Frigola, Norma Fàbregas-Vallvé, Konstantinos G. Alexiou, Nuria López-Bigas, Susana Rivas, Alain Jauneau, Jan U. Lohmann, Philip N. Benfey, Marta Ibañes, Ana I. Caño-Delgado Regulation of Plant Stem Cell Quiescence by a Brassinosteroid Signaling Module Developmental Cell, Volume 33, Issue 2, 20 April 2015, Pages 238.The quiescent center (QC) maintains the activity of the surrounding stem cells within the root stem cell niche, yet specific molecular players sustaining the low rate of QC cell division remain poorly understood. Here, we identified a R2R3-MYB transcription factor, BRAVO (BRASSINOSTEROIDS AT VASCULAR AND ORGANIZING CENTER), acting as a cell-specific repressor of QC divisions in the primary root of Arabidopsis. Ectopic BRAVO expression restricts overall root growth and ceases root regeneration upon damage of the stem cells, demonstrating the role of BRAVO in counteracting Brassinosteroid (BR)-mediated cell division in the QC cells. Interestingly, BR-regulated transcription factor BES1 (BRI1-EMS SUPRESSOR 1) directly represses and physically interacts with BRAVO in vivo, creating a switch that modulates QC divisions at the root stem cell niche. Together, our results define a mechanism for BR-mediated regulation of stem cell quiescence in plants.J.V.-B. and N.F.-V. are funded by FI PhD fellowship from the Generalitat de Catalunya (GC) in the A.I.C.-D. laboratory. J.V.-B. received a short-term fellowship (BE1-00924) in the Lohmann (J.U.L.) laboratory supported by the SFB873 of the DFG. Research by D.F and M.I. is funded by FIS2012-37655-C02-02 by the Spanish Ministry de Economy and Competitiveness and 2009SGR14 from GC, and D.F. has a PhD fellowship (FPU-AP2009-3736). S.R. is funded by the Laboratoire d’Excellence (LABEX) TULIP (ANR-10-LABX-41). M.-P.G.-G. received a “Juan de la Cierva” postdoctoral contract from the Spanish Ministry of Science in the Ana Caño (A.I.C.-D.) laboratory, and an HFSP short-term fellowship in the Benfey (P.N.B.) laboratory. P.N.B. is funded by NSF Arabidopsis 2010 grant. Work in the Ana Caño (A.I.C.-D.) laboratory is funded by a BIO2010/007 grant from the Spanish Ministry of Innovation and Science and a Marie-Curie Initial Training Network “BRAVISSIMO” (grant no. PITN-GA-2008-215118).Peer reviewe

Identificació i caracterització funcional dels complexes proteics dels receptors BRL1 i BRL3 en el teixit vascular d’Arabidopsis Thaliana

Els esteroids juguen papers clau en el creixement I el desenvolupament d’eucariotes multicel•lulars. En plantes, aquestes hormones, anomenades Brassinosteroides (BRs), estan involucrades en una gran varietat de processos biològics essencials per a les plantes. S’han descrit anteriorment dos receptors de BRs del tipus Leucine Rich Repeat Receptor Like Kinase LRR-RLK, BRASSINOSTEROID RECEPTOR LIKE 1 i 3 (BRL1 i BRL3 respectivalemt) que són homòlegs al receptor principal BRI1 i són necessaris pel desenvolupament vascular. Tot i que els principals components de la senyal ja han estat identificats pel seu homòleg més pròxim, el receptor BRI1, els complexes de BRL1 i BRL3 juntament amb els candidats co-receptors així com els components de la ruta de senyalització encara no han sigut identificats. Per tal d’entendre millor la funció molecular d’aquests receptors de BRs en la planta aquesta tesis doctoral planteja dues aproximacions: com a primera aproximació, vaig realitzar un estudi fenotípic del desenvolupament del teixit vascular a la planta model Arabidopsis thaliana (Arabidopsis). Disposant d'una amplia bateria de mutants de síntesis de la hormona i senyalització del receptor BRI1, vam analitzar quantitativament el seu patró vascular a la tija d'Arabidopsis. Vam establir els paràmetres en les plantes silvestres [Col-0 wild type, (WT)] i els vam analitzar a tots i cadascun dels mutants. Això conjuntament amb una col•laboració amb la Dr. Marta Ibañes, física de la Universitat de Barcelona que va construir un model matemàtic per simular la formació del patró vascular ens va permetre el•laborar una hipòtesis que vam demostrar experimentalment i va ser publicada a la revista PNAS. Posteriorment vam observar que les plantes knock-out d'aquests dos receptors BRL1 y BRL3 a diferència de BRI1, no tenien cap fenotip obvi en el teixit vascular de la planta adulta. Així, a continuació, per entendre quina necessitat té la planta de disposar de tres receptors tant altament homòlegs que poden percebre la mateixa hormona, vam utilitzar una aproximació bioquímica en col•laboració amb el Prof. de Vries de la Universitat de Wageningen (Holanda) per tal de purificar els complexes dels receptors in vivo i els seus interactors. Això ens ha permès entendre millor el paper funcional d'aquests receptors en la planta. Els resultats d’aquests experiments estan resumits en un article en preparació que aviat estarà en revisió.Steroid hormones play key roles in growth and development of multicellular eukaryotes. In plant, steroid hormones are called Brassinosteroids (BRs) and are involved in a variety of biological processes. Previously described BRL1 and BRL3 BR receptors are the closest homologues to the main BRI1 receptor. They have been shown to participate in the vascular development of the adult plant shoot stem (Caño-Delgado 2004). While most of the signalling components have been already identified for BRI1 main receptor, BRL1 and BRL3 receptor complexes together with the downstream signalling components remain still unknown. To better understand the role of these BRs receptors in planta we took two different approaches: First, we analysed the phenotype of the vascular tissue in the model plant Arabidopsis thaliana. We quantitatieveley analysed the shoot stem vascular pattern of several Brassinosteroid signalling and synthesis mutants available in our lab. First we stablished the parameters to be analysed in the Col-0 Wild type (WT) plants, which were next analysed and quantified in the BR mutants. This, together with the collaboration of the physicist Dr. Marta Ibañes from the Universitat de Barcelona (UB) who built up a mathematical model that simulated the establishment of the vascular pattern, permitted us to elaborate an hipothesis that we demostrated experimentally and was published in the PNAS journal. Next, we observed that, in contrast to BRI1, the knock-out plants of these two receptors showed no obvious phenotype in the vasular tissue of the adult plant. Thus, in order to better understand why the plant need three different and high homologous receptors, we took a biochemical approach in collaboration with the Professor Sacco de Vries from Wageningen University (WUR) in order to purify the receptor complexes in vivo and their interactors. This allowed us to understand better the role of these receptors in the plant. The results are summarized in an article in process that will be submitted soon

Turning on the microscope turret: a new view for the study of brassinosteroid signaling in plant development

Brassinosteroid (BR) hormones are essential for plant growth and development. In Arabidopsis, the general understanding of BR signaling has been greatly attained by genetic and biochemical approaches that led to the identification of central BR signaling components, from the BRI1 receptor at the plasma membrane to downstream acting BR-regulated BRZ1 and BES1 transcription factors in the nuclei. Recently, an emerging trend is being established to further advance our understanding of the BR signaling pathway in plant development. Scientists have turned on the microscope lens turret to revisit the pleiotropic phenotypes of the BR mutants at a higher magnification, uncovering novel and specific cellular defects in the plant. In-depth phenotypic analysis in combination with the search for cell-specific signaling components that are responsible for those particular defects in the mutants are leading to: (1) definition of novel roles for BRs in vascular development, (2) unraveling BR function in cell division through quantitative analysis of Arabidopsis root growth, (3) establishment of a molecular connection between known patterning and BR-signaling components in organ boundary and stomata development and (4) development of novel strategies toward the identification of BR signaling components with spatiotemporal resolution. In this review, we highlight the importance of these emerging studies to investigate the spatiotemporal control of BR pathways in plant development.N. F. is funded by an FI PhD fellowship from the Generalitat de Catalunya. A. I. C. -D. is recipient of a Marie-Curie Initial Training Network ‘BRAVISSIMO’ (Grant PITN-GA-2008-215118) and a from the Spanish Ministry of Education and Science (BIO2010/00505).Peer reviewe

A method for improving the water-use efficiency and drought tolerance in plants

The current invention relates to the field of plant biology, breeding and agriculture. The invention also relates to methods of generating a drought resistant plant or improving water use efficiency in plants, in particular methods involving down regulating and up regulation of brassinosteroid signaling.Peer reviewedCSIC-IRTA-UAB-UB - Centre de Recerca Agrigenómica (CRAG), Fundación Privada Renta Corporación, Consejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

Transcriptomic study of Arabidopsis roots overexpressing the brassinosteroid receptor BRL3, in control conditions and under severe drought [Dataset]

28 days old root system were collected from soil, quickly washed in water and flash-frozen. Experiment with a bifactorial design. Factor one is the genotype, which include WT (Col-0) and 35S:BRL3. Factor two is the condition, which include control (Properly watered) and 5 days of drought (water-hold) conditions. 3 Biological replicates were collected per each genotype and condition. -- Organism: Arabidopsis thaliana. -- Experiment type: Expression profiling by high throughput sequencing.Resources available on the publisher's site: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE119382Drought is the primary cause of global agricultural losses and represents a major threat to worldwide food security. Currently, plant biotechnology stands out as the most promising strategy to increase crop growth in rain-fed conditions. The main mechanisms underlying drought resistance have been uncovered by studies of plant physiology and by engineering crops with drought-resistant genes. However, plants with enhanced drought resistance usually display lower levels of growth, highlighting the need to search for novel strategies capable of uncoupling drought resistance from growth. Here, we show that the brassinosteroid family of receptors, in addition to promoting growth, guides phenotypic adaptation to a great variety of drought stress traits analyzed herein. Whilst mutations in the ubiquitously localized BRI1 receptor pathway show an enhanced drought resistance at the expense of plant growth, we found that vascular-enriched BRL3 receptors confer drought tolerance without penalizing overall growth. Systematic analyses reveal that upon drought stress the BRL3 receptor pathway triggers the synthesis and mobilization of osmoprotectant metabolites, mainly proline and sugars. This preferentially occurs in the vascular tissues of the roots and favors overall plant growth. Altogether, our results uncover a new role for the spatial control of BR signaling in drought tolerance, and offer a novel strategy to address food security issues in an increasingly water-limited climate.Peer reviewe

Experimental and theoretical methods to approach the study of vascular patterning in the plant shoot

The plant vascular system provides transport and mechanical support functions that are essential for suitable plant growth and development. In Arabidopsis thaliana (Arabidopsis), the vascular tissues at the shoot inflorescence stems are disposed in organized vascular bundles. The vascular patterning emergence and development within the shoot inflorescence stems is under the control of plant growth regulators (De Rybel et al., Nat Rev Mol Cell Biol 17:30–40, 2016; Caño-Delgado et al., Annu Rev Cell Dev Biol 26:605–637, 2010). By using a combined approach of experimental methods for vascular tissues visualization and quantification together with theoretical methods through mathematical and computational modeling, we have reported that auxin transport and brassinosteroid signaling play complementary roles in the formation of the periodic vascular patterning in the shoot (Ibañes et al., Proc Natl Acad Sci U S A 106:13630–13635, 2009; Fàbregas et al., Plant Signal Behav 5:903–906, 2010; Fàbregas et al., PLoS Genet 11:e1005183, 2015). Here, we report the methodology for the interdisciplinary analysis of the shoot vascular patterning in the plant model Arabidopsis into a handle procedure for visualization, quantification, data analysis, and modeling implementation.We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa Programme for Centres of Excellence in R&D” 2016–2019 (SEV‐2015‐0533)”. N.F. is funded by “Fundación RENTA CORPORACIÓN” charity in A.C.-D. Lab. P.F.-J. acknowledges the postdoctoral fellowship provided by the Herchel Smith Foundation. P.F.-J and M.I. acknowledge support from the Spanish Ministry of Economy and Competitiveness through grants FIS2012-37655-C02-02 and FIS2015-66503-C3-3-P and to the Generalitat de Catalunya through Projecte Consolidat 2014 SGR 878. A.I.C.-D. lab is funded by a BIO2013-43873 grant from the Spanish Ministry of Economy and Competitiveness, and the European Research Council by the ERC Consolidator Grant (ERC-2015-CoG—683163).Peer reviewe

The primary root of Sorghumbicolor (L. Moench) as a model system to study brassinosteroid signaling in crops

Roots anchor plants to the soil and are essential for a successful plant growth and adaptation to the environment. Research on the primary root in the plant model system Arabidopsis thaliana has yielded important advances in the molecular and cellular understanding of root growth and development. Several studies have uncovered how the hormones brassinosteroids (BRs) control cell cycle and differentiation programs through different cell-specific signaling pathways that are key for root growth and development. Currently, an important challenge resides in the translation of the current knowledge on Arabidopsis roots into agronomically valuable species to improve the agricultural production and to meet the food security goals of the millennium. In this chapter, we characterize the primary root apex of the cereal Sorghum bicolor (L. Moench) (sorghum), analyze the physiological response of sorghum roots to BRs, and examine the phylogeny of the BRASSINOSTEROID INSENSITIVE1-like receptor family in Arabidopsis and its orthologous genes in sorghum. Overall, we support the use of sorghum as a suitable crop model species for the study of BR signaling in root growth and development. The methods presented enable any laboratory worldwide to use sorghum primary roots as a favorite organ for the study of growth and development in crops.We acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa Programme for Centres of Excellence in R&D” 2016–2019 (SEV-2015-0533).” N.F. is indebted to the “Fundación Renta Corporation” charity and F.L-E and D.B-E. are funded by a BIO2013-43873 grant and a “Retos Colaboración” project (RTC-2014-1916-2) from the Spanish Ministry of Economy and Competitiveness, respectively. A.I.C.-D. is the recipient of a European Research Council, ERC Consolidator Grant (ERC-2015-CoG – 683163).Peer reviewe

The BRASSINOSTEROID INSENSITIVE1–LIKE3 signalosome complex regulates Arabidopsis root development

Brassinosteroid (BR) hormones are primarily perceived at the cell surface by the leucine-rich repeat receptor-like kinase BRASSINOSTEROID INSENSITIVE1 (BRI1). In Arabidopsis thaliana, BRI1 has two close homologs, BRI1-LIKE1 (BRL1) and BRL3, respectively, which are expressed in the vascular tissues and regulate shoot vascular development. Here, we identify novel components of the BRL3 receptor complex in planta by immunoprecipitation and mass spectrometry analysis. Whereas BRI1 ASSOCIATED KINASE1 (BAK1) and several other known BRI1 interactors coimmunoprecipitated with BRL3, no evidence was found of a direct interaction between BRI1 and BRL3. In addition, we confirmed that BAK1 interacts with the BRL1 receptor by coimmunoprecipitation and fluorescence microscopy analysis. Importantly, genetic analysis of brl1 brl3 bak1-3 triple mutants revealed that BAK1, BRL1, and BRL3 signaling modulate root growth and development by contributing to the cellular activities of provascular and quiescent center cells. This provides functional relevance to the observed protein–protein interactions of the BRL3 signalosome. Overall, our study demonstrates that cell-specific BR receptor complexes can be assembled to perform different cellular activities during plant root growth, while highlighting that immunoprecipitation of leucine-rich repeat receptor kinases in plants is a powerful approach for unveiling signaling mechanisms with cellular resolution in plant development.S.D.C., T.E.N., and M.B.G. are funded by grants from the U.S. National Science Foundation (MCB-1021363 and DBI-1126244). N.F. is funded by an Formació de personal Investigador PhD fellowship from the Generalitat de Catalunya. A.I.C.-D. and S.d.V. are recipients of a Marie-Curie Initial Training Network “BRAVISSIMO” (Grant PITN-GA-2008-215118). S.d.V. was a sabbatical professor funded by AGAUR (Generalitat de Catalunya) in A.I.C.-D.'s lab. A.I.C.-D. is funded by a grant from the Spanish Ministry of Education and Science (BIO2010/00505).Peer reviewe