Modulation of primary meristem activity by gibberellins through DELLA-TCP interaction in Arabidopsis

Plant development is an iterative process of organ formation from the primary meristems of the plant. Meristem activity is driven by dynamic transcriptional programs that determine cell fate and identity as cells are displaced trough the meristematic tissue to initiate organ primordia. This regulatory network includes members of the TCP and KNOX family of transcription factors, and integrates external and intrinsic cues to efficiently adapt meristem activity to an ever-changing environment. However, how this integration occurs is not clear yet. DELLA proteins have been proposed to modulate transcriptional circuits in plants in response to environmental signals. Although they do not show DNA binding capacity, DELLAs regulate transcription through physical interaction with a large number of DNA-binding transcription factors and other transcriptional regulators. Given the observed interaction between DELLAs and several members of the TCP family of transcription factors, we have explored the relevance of this interaction in the regulation of primary meristems. We have confirmed that DELLAs interact with members of both Class I and Class II TCPs, and prevent their ability to regulate downstream targets. In the embryonic roots, DELLAs maintain a dormant meristem by impairing TCP14/15-dependent activation of cell-cycle genes. On the other hand, DELLAs participate in the establishment of the shoot apical meristem domain that keeps an indeterminate fate, through the control of KNAT1 gene expression by the TCP2/4-AS1 regulatory module. In summary, this Thesis provides a mechanistic framework to eventually explain environmental regulation of meristem activity.El desarrollo de las plantas es un proceso iterativo de formación de órganos a partir de los meristemos primarios de la planta. La actividad meristemática está dirigida por programas transcripcionales dinámicos que determinan el destino y la identidad celular conforme las células son desplazadas a través del tejido meristemático para iniciar el primordio del órgano. Esta red regulatoria incluye miembros de las familias de factores de transcripción TCP y KNOX, e integra señales externas e intrínsecas para adaptar eficientemente la actividad meristemática al medio ambiente, siempre cambiante. Sin embargo, la manera en que esta integración ocurre no se ha desvelado todavía. Se ha propuesto que en plantas, las proteínas DELLA modulan los circuitos transcripcionales en respuesta a señales medioambientales. Aunque no muestran capacidad de unión al ADN, las DELLAs regulan la transcripción a través de su interacción física con un gran número de factores de transcripción capaces de unirse al ADN y otros reguladores transcripcionales. Dada la interacción observada entre las DELLA y varios miembros de la familia de factores de transcripción TCP, hemos explorado la relevancia de esta interacción en la regulación de los meristemos primarios. Hemos confirmado que las DELLA interaccionan con miembros de las dos clases de TCPs (Clase I y Clase II) e impiden su capacidad de regular dianas aguas abajo. En la raíz del embrión, las DELLAs mantienen el meristemo durmiente al impedir la activación de los genes de ciclo celular dependiente del módulo TCP14/15. Por otro lado, las DELLAs participan en el establecimiento del meristemo apical del tallo, que mantiene un estado indiferenciado, a través del control el módulo TCP2/4-AS1, el cual regula la expresión del gen KNAT1. En resumen, esta Tesis aporta un marco mecanístico para explicar, con el tiempo, la regulación medioambiental de la actividad meristemática.El desenvolupament de les plantes consiteix en un procés iteratiu de formació d'órgans a partir dels meristems primaris. L'activitat meristemàtica està diridida per programes transcripcionals dinàmics que determinen el destí i la identitat cel.lular a mesura que les cèl.lules es van allunyant del meristem per formar els primordis d`órgans. Esta xarxa de regulació inclou membres de les famílies de factors de transcripció TCP i KNOX, i integra senyals externes i intrínseques per adaptar d'una manera eficient l'activitat del meristem als canvis del medi ambient. No obstant, no es coneix de quina manera la planta fa esta integració. S'ha proposat que les proteïnes DELLA modulen estes xarxes transcripcionals en resposta a senyals del medi. Estes proteïnes no tenen capacitat d'unir-se a l'ADN, però regulen la transcripció mitjançant la interacció amb factors de transcripció i altres reguladors transcripcionals. Donada la interacció entre les proteïnes DELLA i alguns membres de la família de factors de transcripció TCP, hem explorat la rellevància d'esta interacció a la regulació dels meristems primaris. Hem confirmat que les DELLA interaccionen amb membres de les dos classes de TCPs (Classe I i Classe II) i els impedeixen regular les seues dianes. A l'arrel de l'embrió, les DELLA mantenen el meristem dorment al impedir l'activació de gens del cicle cel.lular depenent del mòdul TCP14/15. Per una altra banda, les DELLA particípen a l'establiment del meristem apical de la tija, al que mantenen en un estat indiferenciat, mitjançant el control del mòdul TCP2/4-AS1, que regula l'expressió de KNAT1. En resum, esta Tesi aporta un marc mecanístic per poder explicar, més endavant, la regulació mediambiental de l'activitat meristemàtica.Felipo Benavent, A. (2017). Modulation of primary meristem activity by gibberellins through DELLA-TCP interaction in Arabidopsis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/82237TESI

Caracterización de las alteraciones en el miRNoma de un modelo de distrofia miotónica en Drosophila melanogaster

En un modelo de distrofia miotónica en Drosophila melanogaster se observó que la alteración de los microRNAs podría contribuir a la enfermedad. En este trabajo se pretende evaluar el origen de las alteraciones en el miRNoma de dichas moscas. En concreto, se testa si las proteínas Muscleblind y TBPH están implicadas en la biogénesis de estos miRNAs.Felipo Benavent, A. (2011). Caracterización de las alteraciones en el miRNoma de un modelo de distrofia miotónica en Drosophila melanogaster. http://hdl.handle.net/10251/11649Archivo delegad

Linking plant metabolism and immunity through methionine biosynthesis

We thank the Spanish Research Agency (AEI) for financial support (RTI2018-098501-B-100) . No conflict of interest declared.Escaray, F.; Felipo-Benavent, A.; Vera Vera, P. (2022). Linking plant metabolism and immunity through methionine biosynthesis. Molecular Plant. 15(1):6-8. https://doi.org/10.1016/j.molp.2021.12.0076815

Expanded CTG repeats trigger miRNA alterations in Drosophila that are conserved in myotonic dystrophy type 1 patients

Myotonic dystrophy type 1 (DM1) is caused by the expansion of CTG repeats in the 3' untranslated region of the DMPK gene. Several missplicing events and transcriptional alterations have been described in DM1 patients. A large number of these defects have been reproduced in animal models expressing CTG repeats alone. Recent studies have also reported miRNA dysregulation in DM1 patients. In this work, a Drosophila model was used to investigate miRNA transcriptome alterations in the muscle, specifically triggered by CTG expansions. Twenty miRNAs were differentially expressed in CTG-expressing flies. Of these, 19 were down-regulated, whereas 1 was up-regulated. This trend was confirmed for those miRNAs conserved between Drosophila and humans (miR-1, miR-7 and miR-10) in muscle biopsies from DM1 patients. Consistently, at least seven target transcripts of these miRNAs were up-regulated in DM1 skeletal muscles. The mechanisms involved in dysregulation of miR-7 included a reduction of its primary precursor both in CTG-expressing flies and in DM1 patients. Additionally, a regulatory role for Muscleblind (Mbl) was also suggested for miR-1 and miR-7, as these miRNAs were down-regulated in flies where Mbl had been silenced. Finally, the physiological relevance of miRNA dysregulation was demonstrated for miR-10, since over-expression of this miRNA in Drosophila extended the lifespan of CTG-expressing flies. Taken together, our results contribute to our understanding of the origin and the role of miRNA alterations in DM1. © The Author 2012. Published by Oxford University Press. All rights reserved.Fundacion Ramon Areces; Generalitat Valenciana (Prometeo/2010/081); Ministerio de Ciencia e Innovacion (SAF2006-09121) in collaboration with the biotechnology company Sistemas Genomicos S.L.; FIS (FIS09-00660) ; Isabel Gemio Foundation; Accion Especial de Enfermedades Raras ‘Cetegen’ by Genoma Espana Foundation; Generalitat Valenciana; Fundacion Ramon Areces; Banca Civica; Basque Government (AE-BFI-08.164); ISCIII; Ministerio de Economia y CompetitividadPeer Reviewe

A quantitative gibberellin signalling biosensor reveals a role for gibberellins in internode specification at the shoot apical meristem

Growth at the shoot apical meristem (SAM) is essential for shoot architecture construction. The phytohormones gibberellins (GA) play a pivotal role in coordinating plant growth, but their role in the SAM remains mostly unknown. Here, we developed a ratiometric GA signalling biosensor by engineering one of the DELLA repressors, to suppress its master regulatory function in GA transcriptional responses while preserving its degradation upon GA sensing. We demonstrate that this novel degradation-based biosensor accurately reports on cellular changes in GA levels and perception during development. We used this biosensor to map GA signalling activity in the SAM. We show that high GA signalling is found primarily in cells located between organ primordia that are the precursors of internodes. By gain- and loss-of-function approaches, we further demonstrate that GAs regulate cell division plane orientation to establish the typical cellular organisation of internodes, thus contributing to internode specification in the SAM

A quantitative gibberellin signaling biosensor reveals a role for gibberellins in internode specification at the shoot apical meristem.

Acknowledgements: We thank the colleagues of the Laboratoire Reproduction et Développement des Plantes and the Institut de Biologie Moléculaire des Plantes for fruitful discussions on this work and for sharing material and advice. We thank Mathilde Sirlin-Josserand for her help with graphical representation and statistics in Figs. 1f, g, and 2c, and in Supplementary Fig. 2g. We also thank Miguel Perez-Amador, Jan Lohmann, Yvon Jaillais, Tai-ping Sun, Miguel Blazquez, David Alabadi, and the NASC for seeds and plasmids. We thank the personnel of SFR Biosciences (UMS3444/CNRS, US8/Inserm, ENS de Lyon, UCBL) facility PLATIM, and especially Jacques Brocard, for assistance with microscopy and image analysis. We also thank Claire Lionnet for her help with image analysis. This work was supported by the ANR-16-CE13-0014 (GrowthDynamics) grant to T.V. and P.A.; a European Research Council grant (GAtransport) to R.W.; a Guangdong Laboratory for Lingnan Modern Agriculture Grant NG2021001 to B.S.; a grant from the Israel Science Foundation (grant no. 1057/21) to R.W.Funder: Guangdong Laboratory for Lingnan Modern Agriculture Grant NG2021001Growth at the shoot apical meristem (SAM) is essential for shoot architecture construction. The phytohormones gibberellins (GA) play a pivotal role in coordinating plant growth, but their role in the SAM remains mostly unknown. Here, we developed a ratiometric GA signaling biosensor by engineering one of the DELLA proteins, to suppress its master regulatory function in GA transcriptional responses while preserving its degradation upon GA sensing. We demonstrate that this degradation-based biosensor accurately reports on cellular changes in GA levels and perception during development. We used this biosensor to map GA signaling activity in the SAM. We show that high GA signaling is found primarily in cells located between organ primordia that are the precursors of internodes. By gain- and loss-of-function approaches, we further demonstrate that GAs regulate cell division plane orientation to establish the typical cellular organization of internodes, thus contributing to internode specification in the SAM