REGULATION OF TRANSLATION DURING ABIOTIC STRESS CONDITIONS IN PLANTS

Personnel:

GENERAL OVERVIEW

Only the precise knowledge of how plants respond to stress will allow the correct selection and use of crop varieties better adapted to adverse environments.

Most plants complete their life cycle in a single location and, therefore, their development and reproduction depend on the environmental conditions they are exposed to. Environmental stresses such as drought, high and low temperatures, saline soils, etc., seriously affect plant development and growth.

To cope with these challenges, plants have evolved genetically based physiological, biochemical and molecular strategies that allow them to survive under such adverse conditions. One of the earliest plant responses to environmental stresses is global inhibition of protein synthesis, allowing the specific translation of some mRNAs involved in the response to stress. Despite the importance of this response, the knowledge about the mechanisms involved in this translational regulation is very poor in plants. Our lab is mainly focused on characterising the mechanisms involved in this translational regulation and, based on this information, identifying new regulators of the stress response in plants. Our final goal is to contribute to understand how plants respond to stress in order to select better environmentally adapted crops, and in such a way improving crop security and production.


RESEARCH ACTIVITY

Identification of new regulators involved in the adaptation to stress in plants

In order to identify new regulators of the heat stress response in plants, we firstly carried out a high-throughput translatome analysis in Arabidopsis seedlings subjected to a moderate heat stress (Yangüez et al., 2013). From this study we identified different mRNAs that were highly translated under a strong general translational inhibition.

In addition, and with the same objective, we have carried out a comparative proteomics analysis of plants grown under control conditions, during a heat acclimation event (38°C for 1 h) and at the early stages of the recovery periods that selectively lead plants to either survival or death (Figure 1). This quantitative proteomics analysis allowed us to: (1) get a deeper insight of the proteins regulating the acclimation process, (2) unravel the common and specific proteins involved in each of the cited response to heat and (3) identify pivotal proteins involved specifically in the commitment to plant survival or death in response to heat (Echevarría-Zomeño et al., 2016).

These two studies granted the selection of new potential regulators of plant adaptation to stress for further studies.

 


Figure 1. (A) 7 day-old Arabidopsis seedlings were subjected to the stress treatments represented in the figure that leads to plant survival (A) or death (B). Photographs of the plants taken after 5 h and 7 days from the exposure to 45°C. The samples subjected to iTRAQ analysis correspond to C (control), A (acclimated), CS (committed to plant survival, 5h after the 45°C treatment in (A)) and CD (committed to plant death, 5 h after the 45°C treatment in (B). At this early time point the plants, although committed to finally die, are still green and healthy). (C) Those proteins identified as differentially accumulated were grouped into clusters based on their changing pattern in A, CS and CD relative to control. (D) Thermotolerance assay of two different mutants in genes encoding for proteins identified in our study but whose role in plant thermotolerance was previosusly unknown. These assays demonstrate that this study reveals new positive and negative regulators of thermotolerance in plants.


HOP3 a new regulator of the ER stress response in plants

HOPs (HSP70-HSP90 organizing proteins) are a highly conserved family of cytosolic cochaperones, whose role in adaptation to stress was not previously evaluated in plants. In a recent study by Fernández-Bautista et al., we showed that HOP3, one member of the HOP family in Arabidopsis, plays an essential role during ER stress in plants. HOP3 interacts in vivo with cytosolic HSP90 and HSP70, indicating that it is a functional member of the HOP family in Arabidopsis. Interestingly, we showed that HOP3 interacts specifically with BiP, a major ER chaperone. BiP belongs to the Hsp70 family, however, it lacks the conserved octapeptide sequence that has been involved in the interaction between HSP70 and HOP in other species, making this interaction completely unexpected. Despite the lack of this conserved sequence, interaction analyses indicate that HOP3 binds to the nucleotide binding domain of BiP, demonstrating a noncanonical HOP binding to this major ER-resident protein. Consistent with the interaction with BiP, HOP3 is partly localized at the endoplasmic reticulum (ER). Moreover, HOP3 is induced both at transcript and protein levels by UPR inducer agents. More importantly, hop3 loss-of-function mutants show a hypersensitive phenotype in the presence of the ER stress inducer agents, demonstrating that this protein plays an essential role during the ER stress response. In line with this observation, the hop3-1 mutant shows a reduction in pollen germination, a developmental process especially vulnerable to disturbances in ER protein homeostasis. These findings open the exciting possibility that HOP3, through its role in the alleviation of ER stress, could play an important function during specific developmental programs and in response to different environmental stresses.


Figure 2. HOP3 is localized at the ER and plays an important role during the ER stress in plants. (A) HOP3 colocalizes at the ER with RFP-ER, an especific ER marker protein. (B) hop3 mutants show a hypersensibility to ER stress inducer agents, demonstrating the main role of HOP3 in the alleviation of ER stress in plants.

 

Other players involved in plant adaptation to heat

In addition to HOP3, the previously described approaches (Yángüez et al., 2013; Echevarría-Zomeño et al., 2016) allowed the identification of other proteins potentially involved in plant adaptation to heat. Specifically, our lab is highly interested in the characterization of new proteins involved in thermomorphogenesis, a response that allow plants to adapt to moderate increases of temperature as those associated to the current models of climate change.

Characterization of the molecular mechanisms that regulate translation initiation under environmental and developmental cues

One of the earliest responses of plants to stress is the regulation of protein synthesis. This regulation takes place mainly at the initiation step of protein translation. In mammals, one of the main mechanisms for translation regulation are the control of eIF4E activity by interaction with other proteins (4E-BPs and 4E-binding partners in Figure 3). Despite the broad function of these eIF4E interacting proteins in the regulation of general and specific inhibition of translation in other eukaryotes, no orthologs have been found in plants. In our lab, we are interested in characterising the mechanisms involved in the regulation of translation initiation under different stress conditions and during specific developmental programs in plants. Our data suggest that, in contrast to the general view, the regulation of translation initiation is not so conserved in plants as in other eukaryotes, highlighting the extraordinary importance of identifying and characterising these mechanisms in the green land.

In addition, our lab is also focused on the identification of those mRNAs that are translationally regulated during specific stages of development and in response to environmental cues. In this regard, our lab has implemented the RiboSeq technique that allows the determination of exact ribosome positions on a genome wide scale at single-codon resolution.


Research Projects

   

  • Evaluación del potencial biotecnológico de la proteína 3P para aumentar la tolerancia de las plantas a altas temperaturas y a patógenos. 2014-2017 (RTA2013-00027-00-00). PI: M. Castellano.

  • Estudio de la regulacion del factor de iniciacion de la traduccion IF4E en respuesta a estres abiotico en plantas. MICINN (BIO2010-15751), 2011-2013, PI: M. Castellano.

 

 

 
 

Representative Publications

Sesma, A; Castresana, C; Castellano, MM. 2017. "Regulation of translation by TOR, eIF4E and eIF2α in plants: current knowledge, challenges and future perspectives". Frontiers in Plant Science. DOI: 10.3389/fpls.2017.00644".

Fernández-Bautista, N; Fernández-Calvino, L; Muñoz, A; Castellano, MM. 2017. "HOP3 a new regulator of the ER stress response in Arabidopsis with possible implications in plant development and response to biotic and abiotic stresses". Plant Signaling & Behavior. DOI: 10.1080/15592324.2017.1317421".

Álvarez-Aragón, R; Rodríguez-Navarro, A. 2017. "Nitrate-dependent shoot sodium accumulation and osmotic functions of sodium in Arabidopsis under saline conditions". Plant Journal. DOI: 10.1111/tpj.13556".

Fernández-Bautista, N; Fernández-Calvino, L; Muñoz, A; Castellano, MM. 2017. "AtHOP3, a member of the HOP family in Arabidopsis, interacts with BiP and plays a major role in the ER stress response". Plant, Cell & Environment. DOI: 10.1111/pce.12927".

Fernández-Bautista, N; Domínguez-Núñez, JA; Castellano Moreno, MM; Berrocal-Lobo, M. 2016. "Plant tissue trypan blue staining during phytopathogen infection". Bio-protocol. DOI: 10.21769/BioProtoc.2078".

Toribio, R; Muñoz, A; Castro-Sanz, AB; Ferrando, A; Berrocal-Lobo, M; Castellano, MM. 2016. "Evolutionary aspects of translation regulation during abiotic stress and development in plants", p. 477-490. In G. Hernández and R. Jagus (eds.), Evolution of the Protein Synthesis Machinery and Its Regulation. Springer International Publishing, Cham. DOI: 10.1007/978-3-319-39468-8_18".

Echevarría-Zomeño, S; Fernández-Calvino, L; Castro-Sanz, AB; López, JA; Vázquez, J; Castellano, MM. 2015. "Dissecting the proteome dynamics of the early heat stress response leading to plant survival or death in Arabidopsis". Plant, Cell & Environment. DOI: 10.1111/pce.12664".

D'Amelia, V; Aversano, R; Batelli, G; Caruso, I; Castellano, MM; Castro-Sanz, AB; Chiaiese, P; Fasano, C; Palomba, F; Carputo, D. 2014. "High AN1 variability and interaction with basic helix-loop-helix co-factors related to anthocyanin biosynthesis in potato leaves". Plant Journal. DOI: 10.1111/tpj.12653".

Catalá, R; López-Cobollo, R; Castellano, MM; Angosto, T; Alonso, JM; Ecker, JR; Salinas, J. 2014. "The Arabidopsis 14-3-3 protein RARE COLD INDUCIBLE 1A links low-temperature response and ethylene biosynthesis to regulate freezing tolerance and cold acclimation". Plant Cell. DOI: 10.1105/tpc.114.127605".

Echevarría-Zomeño, S; Belda-Palazón, B; Castellano, MM; Ferrando, A. 2014. "Regulation of translation as an approach to cope with abiotic stress", p. 109-129. In R. K. Gaur and P. Sharma (eds.), Molecular Approaches for Plant Abiotic Stress.

Yángüez, E; Castro-Sanz, AB; Fernández-Bautista, N; Oliveros, JC; Castellano, MM. 2013. "Analysis of genome-wide changes in the translatome of Arabidopsis seedlings subjected to heat stress". PLoS One. DOI: 10.1371/journal.pone.0071425 ".

 

 

 

Centro de Biotecnología y Genómica de Plantas UPM – INIA Parque Científico y Tecnológico de la U.P.M. Campus de Montegancedo
Autopista M-40, Km 38 - 28223 Pozuelo de Alarcón (Madrid) Tel.: +34 91 4524900 ext. 1806 / +34 91 3364539 Fax: +34 91 7157721. Contacto

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