• Si las condiciones ambientales son buenas, las plantas de patata utilizan los azucares en la parte aérea para crecer, mientras que para sobrevivir al invierno los acumulan en tubérculos bajo tierra en forma de almidón
• El gen BRANCHED1b, que regula varios procesos moleculares relacionados con periodos de inactividad vegetal, es también responsable de que los tubérculos se formen bajo tierra

Investigadores del Consejo Superior de Investigaciones Científicas identifican una nueva función del gen BRANCHED1b, que ha resultado ser esencial para la formación de tubérculos bajo tierra. El trabajo, que se publica ahora en Nature Plants  muestra que mutaciones en este gen afectan a la capacidad de distinguir entre tallos aéreos y subterráneos (llamados estolones) en las plantas de patata. De esta manera en las plantas mutantes se produce una distribución errónea de los azucares y de las señales que controlan la formación de tubérculos y estas desarrollan tubérculos aéreos, expuestos a las inclemencias del tiempo y los animales.  

El equipo del CSIC dirigido por Pilar Cubas, en colaboración con el de Salomé Prat, en el Centro Nacional de Biotecnología (CNB-CSIC) ha identificado que el gen llamado BRANCHED1b (BRC1b) es esencial para que los tubérculos se formen únicamente en la parte subterránea de la planta. Cubas explica sus resultados “utilizando como modelo plantas de patata silvestres y mutantes que no expresaban este gen, estudiamos la formación de tallos aéreos y subterráneos (llamados estolones) durante seis semanas. Así observamos que los mutantes producían más tallos aéreos, pero menos estolones que las plantas silvestres. Pero el cambio más llamativo se refería a la formación de tubérculos: los mutantes producían muchos menos tubérculos subterráneos y de menor tamaño, y además, empezaron a producir tubérculos aéreos.” 

PLoS Pathog. 2022 Feb 18;18(2):e1010332.

AA Valli, R García López, M Ribaya, FJ Martínez, D García Gómez, B García, I Gonzalo, A Gonzalez de Prádena, F Pasin, I Montanuy, E Rodríguez-Gonzalo, JA García

Abstract

Cassava brown streak disease (CBSD), dubbed the "Ebola of plants", is a serious threat to food security in Africa caused by two viruses of the family Potyviridae: cassava brown streak virus (CBSV) and Ugandan (U)CBSV. Intriguingly, U/CBSV, along with another member of this family and one secoviridae, are the only known RNA viruses encoding a protein of the Maf/ham1-like family, a group of widespread pyrophosphatase of non-canonical nucleotides (ITPase) expressed by all living organisms. Despite the socio-economic impact of CDSD, the relevance and role of this atypical viral factor has not been yet established. Here, using an infectious cDNA clone and reverse genetics, we demonstrate that UCBSV requires the ITPase activity for infectivity in cassava, but not in the model plant Nicotiana benthamiana. HPLC-MS/MS experiments showed that, quite likely, this host-specific constraint is due to an unexpected high concentration of non-canonical nucleotides in cassava. Finally, protein analyses and experimental evolution of mutant viruses indicated that keeping a fraction of the yielded UCBSV ITPase covalently bound to the viral RNA-dependent RNA polymerase (RdRP) optimizes viral fitness, and this seems to be a feature shared by the other members of the Potyviridae family expressing Maf/ham1-like proteins. All in all, our work (i) reveals that the over-accumulation of non-canonical nucleotides in the host might have a key role in antiviral defense, and (ii) provides the first example of an RdRP-ITPase partnership, reinforcing the idea that RNA viruses are incredibly versatile at adaptation to different host setups.

doi: 10.1371/journal.ppat.1010332.

• 17 new vacuolar trafficking mutants identified in Arabidopsis
• This research unveils an unknown compartment of the plant vacuolar trafficking pathway and provides evidence that microtubules and kinesins participate in this process.

Proc Natl Acad Sci U S A. 2020 Apr 22. pii: 201919820.

Delgadillo MO, Ruano G, Zouhar J, Sauer M, Shen J, Lazarova A, Sanmartín M, Lai LTF, Deng C, Wang P, Hussey PJ, Sánchez-Serrano JJ, Jiang L, Rojo E.

Abstract

The factors and mechanisms involved in vacuolar transport in plants, and in particular those directing vesicles to their target endomembrane compartment, remain largely unknown. To identify components of the vacuolar trafficking machinery, we searched for Arabidopsis modified transport to the vacuole (mtv) mutants that abnormally secrete the synthetic vacuolar cargo VAC2. We report here on the identification of 17 mtv mutations, corresponding to mutant alleles of MTV2/VSR4, MTV3/PTEN2A MTV7/EREL1, MTV8/ARFC1, MTV9/PUF2, MTV10/VPS3, MTV11/VPS15, MTV12/GRV2, MTV14/GFS10, MTV15/BET11, MTV16/VPS51, MTV17/VPS54, and MTV18/VSR1 Eight of the MTV proteins localize at the interface between the trans-Golgi network (TGN) and the multivesicular bodies (MVBs), supporting that the trafficking step between these compartments is essential for segregating vacuolar proteins from those destined for secretion. Importantly, the GARP tethering complex subunits MTV16/VPS51 and MTV17/VPS54 were found at endoplasmic reticulum (ER)- and microtubule-associated compartments (EMACs). Moreover, MTV16/VPS51 interacts with the motor domain of kinesins, suggesting that, in addition to tethering vesicles, the GARP complex may regulate the motors that transport them. Our findings unveil a previously uncharacterized compartment of the plant vacuolar trafficking pathway and support a role for microtubules and kinesins in GARP-dependent transport of soluble vacuolar cargo in plants.

doi: 10.1073/pnas.1919820117

• La regulación de la señalización mediada por ácido jasmónico es clave para mantener el equilibrio entre crecimiento y defensa
• Las proteínas BPM regulan la degradación de los factores de transcripción que activan la respuesta inmune.

La supervivencia de las plantas en la naturaleza requiere su adaptación a diferentes tipos de estrés medioambiental. A diferencia de los animales, las plantas no tienen posibilidad de escapar cuando se enfrentan a una agresión externa como la mordedura de un insecto. Por este motivo, han desarrollado mecanismos de señalización interna y respuesta a través de hormonas como el ácido jasmónico. Sin embargo, la respuesta desencadenada por esta hormona frena el crecimiento de la planta para centrar los recursos en la defensa. Así, un exceso de acción de esta hormona puede afectar al desarrollo vegetal, por lo que su señalización debe estar regulada de una manera muy precisa en tiempo e intensidad.

Ahora, investigadores del Centro Nacional de Biotecnología (CNB) pertenecientes al Consejo Superior de Investigaciones Científicas (CSIC) en colaboración con las universidades de Estrasburgo y Navarra han identificado un nuevo mecanismo molecular que modula los pulsos de activación de la hormona. El trabajo, que ha sido publicado en la revista Proceedings of the National Academy of Sciences  (PNAS), da respuesta a cómo se regula la activación de defensas hasta alcanzar un equilibrio entre crecimiento y respuesta a estrés.

Roberto Solano, researcher and current director of the Plant Molecular Genetics Department at  the National Center for Biotechnology (CNB) appears in the list of the highly cited researchers in the field of ​​animal and plant sciences published by Clarivate Analytics.
Dr. Solano is among the 120 Spanish scientists included this year, of which 24 researchers belong to the National Research Council (CSIC). This list identifies approximately 4000 researchers who have demonstrated significant influence in specific fields through publication of multiple highly cited papers during the last decade. This year, as a novelty, 2000 scientists with cross-field impact were identified and added to the classification.

Dr. Solano's research group is focused on studying the molecular mechanisms that allow plants to adapt to the environment. Their efforts have been directed to understand how jasmonate, a plant hormone, is involved in stress responses. His work have led to the identification of the jasmonate active form as well as a family of cue proteins for jasmonate signaling , both in Arabidopsis thaliana and Marchantia polymorpha. These results have been recently publishsed in high impact scientific jorunals as Current Biology, Plant Cell and Molecular Plant.

Front Plant Sci. 2019 Sep 17;10:1095. eCollection 2019.

Fonseca S, Rubio V.

Abstract

CULLIN4 (CUL4) RING ligase (CRL4) complexes contain a CUL4 scaffold protein, associated to RBX1 and to DDB1 proteins and have traditionally been associated to protein degradation events. Through DDB1, these complexes can associate with numerous DCAF proteins, which directly interact with specific targets promoting their ubiquitination and subsequent degradation by the proteasome. A characteristic feature of the majority of DCAF proteins that associate with DDB1 is the presence of the DWD motif. DWD-containing proteins sum up to 85 in the plant model species Arabidopsis. In the last decade, numerous Arabidopsis DWD proteins have been studied and their molecular functions uncovered. Independently of whether their association with CRL4 has been confirmed or not, DWD proteins are often found as components of additional multimeric protein complexes that play key roles in essential nuclear events. For most of them, the significance of their complex partnership is still unexplored. Here, we summarize recent findings involving both confirmed and putative CRL4-associated DCAF proteins in regulating nuclei architecture remodelling, DNA damage repair, histone post-translational modification, mRNA processing and export, and ribosome biogenesis, that definitely have an impact in gene expression and de novo protein synthesis. We hypothesized that, by maintaining accurate levels of regulatory proteins through targeted degradation and transcriptional control, CRL4 complexes help to surveil nuclear processes essential for plant development and survival.

doi: 10.3389/fpls.2019.01095

Front Plant Sci. 2019 Sep 5;10:1044. eCollection 2019.

Contreras R, Kallemi P, González-García MP, Lazarova A, Sánchez-Serrano JJ, Sanmartín M, Rojo E.

Abstract

The transition of stem cells from self-renewal into differentiation is tightly regulated to assure proper development of the organism. Arabidopsis MINIYO (IYO) and its mammalian orthologue RNA polymerase II associated protein 1 (RPAP1) are essential factors for initiating stem cell differentiation in plants and animals. Moreover, there is evidence suggesting that the translocation of IYO and RPAP1 from the cytosol into the nucleus functions as a molecular switch to initiate this cell fate transition. Identifying the determinants of IYO subcellular localization would allow testing if, indeed, nuclear IYO migration triggers cell differentiation and could provide tools to control this crucial developmental transition. Through transient and stable expression assays in Nicotiana benthamiana and Arabidopsis thaliana, we demonstrate that IYO contains two nuclear localization signals (NLSs), located at the N- and C-terminus of the protein, which mediate the interaction with the NLS-receptor IMPA4 and the import of the protein into the nucleus. Interestingly, IYO also interacts with GPN GTPases, which are involved in selective nuclear import of RNA polymerase II. This interaction is prevented when the G1 motif in GPN1 is mutated, suggesting that IYO binds specifically to the nucleotide-bound form of GPN1. In contrast, deleting the NLSs in IYO does not prevent the interaction with GPN1, but it interferes with import of GPN1 into the nucleus, indicating that IYO and GPN1 are co-transported as a complex that requires the IYO NLSs for import. This work unveils key domains and factors involved in IYO nuclear import, which may prove instrumental to determine how IYO and RPAP1 control stem cell differentiation.

doi: 10.3389/fpls.2019.01044.

Plant Cell. 2019 Aug 7. pii: tpc.00974.2018

Peñuelas M, Monte I, Schweizer F, Vallat A, Reymond P, García-Casado G, Franco-Zorrilla JM, Solano R.

Abstract

Jasmonoyl-isoleucine regulates plant immunity, growth and development in vascular plants by activating genome-wide transcriptional reprogramming. In Arabidopsis, this is largely orchestrated by MYC2 and related transcription factors (TFs). However, the TFs activating this pathway in basal plant lineages are currently unknown. We report the functional conservation of MYC-related TFs between the eudicot Arabidopsis thaliana and the liverwort Marchantia polymorpha, which belongs to an early diverging land-plant lineage. Phylogenetic analysis suggests that MYC function first appeared in charophycean algae, and therefore predates the evolutionary appearance of any other jasmonate pathway component. Marchantia possesses two functionally interchangeable MYC genes, one in females and one in males. Similar to AtMYC2, MpMYCs showed nuclear localization, interaction with JAZ-repressors, and regulation by light. Phenotypic and molecular characterization of loss- or gain-of-function mutants demonstrated that MpMYCs are necessary and sufficient for the activation of the pathway in Marchantia, but unlike their Arabidopsis orthologs, do not regulate fertility. Our results show that despite 450 million years of independent evolution, MYCs are functionally conserved between bryophytes and eudicots. Genetic conservation in an early diverging lineage suggests that MYC function existed in the common ancestor of land plants and evolved from a pre-existing MYC function in charophycean algae.

doi: 10.1105/tpc.18.00974

- El equipo de Vicente Rubio  ha identificado un mecanismo por el cual las plantas regulan de manera precisa la respuesta a las variaciones en la disponibilidad del agua.

Los estomas son unos pequeños poros que se encuentran en las hojas y los tallos de las plantas, a través de los cuales se realiza el intercambio gaseoso. Sin embargo, también son la vía por la se pierde el agua a través de la  transpiración. En condiciones de sequía, las plantas cierran los estomas mediante un proceso que está controlado por el ácido abscísico (ABA), una hormona vegetal que se sintetiza cuando la planta detecta la falta de agua.

En el artículo del Dr. Vicente Rubio, publicado en The Plant Cell,  han identificado una factor de Arabidopsis, ALIX, una proteína de membrana que interacciona con los receptores de ABA y regula su tráfico y posterior degradación en la vacuola.