STUDYING GIBBERELLIN SIGNALLING TO IMPROVE SEED GERMINATION AND PLANT GROWTH UNDER STRESS

Personnel:

 

SUMMARY AND RESEARCH LINES

Gibberellins (GAs) are phytohormones required for vegetative and reproductive growth throughout the plant life cycle. GAs regulate gene expression in time and space and their levels can be altered in response to developmental and environmental cues. Several stress conditions, such as drought and salinity, are known to decrease GA biosynthesis and signalling. Although this response increases stress tolerance it reduces plant growth and productivity.

The work in the lab focuses on:

  • Identification and study of the molecular mechanisms underlying GA responses in different tissues and their role in plant growth and development under different environmental conditions.
  • Applying knowledge to improve crop performance.

We are using plant seeds as a model to study the integration of environmental signals into the decision to grow since: i) they require GAs to germinate; ii) the “decision” to germinate represents a critical stage in the life cycle of higher plants and is an important ecological and commercial trait; iii) many of the regulators found in this organ have also been recruited by other developmental stages to play similar roles.

To carry out our research, we are using powerful and complementary approaches, some of them developed in our group (i.e.: Figure 1), and collaborate with a company, national and international groups. Our main research lines are indicated below:

 

Figure 1. Promoter sequences conserved across species are likely to be functionally relevant (A). If so, they should be able to drive expression of reporter genes (i.e.: luciferase) in the studied system (B). Yeast one hybrid screenings of an arrayed library of 1,200 transcription factors (TFs) from Arabidopsis can identify proteins responsible for promoter regulation while filtering genetic redundancy (C). Identified DNA-protein interactions are relevant in planta (D). Castrillo et al (2011).

1.- GA signalling mechanisms in the control of seed germination

We have found that GA-signalling in the Arabidopsis embryo epidermis along the embryonic axis is required for proper germination and uncovered the underlying molecular mechanism which is coordinating growth of the epidermis with that of inner tissues (Figure 2). This mechanism was found later to be conserved in cotton where it controls fibre cell elongation, indicating that it has been recruited by other developmental stages and suggesting that it is highly conserved in plants. Our ongoing studies, suggest that GA-signalling underlying growth of the endosperm is controlled by a set of regulatory genes different to those of the embryo. The full extent to what these mechanisms has been recruited by other developmental stages and/or plant species remains to be determined.

Figure 2. The ATML1 and PDF2 genes (HD-ZIP TFs) are specifically expressed in the epidermis (A: mRNA in situ hybridizations) and their encoded proteins interact with DELLA proteins in yeast and in planta (B: Bimolecular Fluorescence Complementation). According with our results a regulatory model for GA signalling in the epidermis have been proposed (C). Rombolá-Caldentey et al (2014).

2.- GA-signalling and its interaction with stress tolerance

In collaboration with the group of Dr. W. Dröge-Laser we have generated a seed library overexpressing Arabidopsis Transcription Factors(Weiste et al., 2007; now with more than 700 TFs). Screening this library (gain of function) increases the probability of identifying new players in the regulation of germination and GA-signalling that may have been missed by previous screening approaches with loss-of-function mutants (mainly due to genetic redundancy). We have identified mutants able to germinate faster under low GA levels similar to those produced by stress conditions. Remarkably, some of these mutants, currently under study, also have improved vegetative growth suggesting the existence of mechanisms unlinking growth and stress (Figure 3).

Figure 3. Arabidopsis mutants with increased growth under stress. Genetic redundancy masks phenotypes when screening loss-of-function mutants that can be bypassed by screening gain of function mutants. Over 30,000 seeds from a library of transgenic seeds overexpressing TFs (Weiste et al., 2007) were screened for improved germination under stress conditions. Several mutants were also able to grow better during vegetative stages.       

3.- Using molecular and genetic information to improve agronomic performance

Living organisms synthesize a myriad of metabolites required for proper growth and development with many of them able to affect the performance of “neighbours” (i.e.: competitors, predators, symbionts). Compounds from natural sources, such as those derived from plants, are usually biodegradable and considered as more ‘environmentallly friendly’ compared with many traditional herbicides or other chemicals. We have developed “sensor” plant lines and a methodology for high-throughput screening to identify agrobiological compounds (supplied by PRB S.L.) modifying seed germination properties. The identified compounds will also be excellent candidates to regulate growth in other developmental stages and plant species.

POTENTIAL BENEFITS OF OUR RESEARCH
  • Insights into GA signalling have potential applications to improve seed germination and plant growth under normal and stress conditions.
  • Modifying tissue-specific mechanisms will be more compatible with normal plant development compared to global alterations of gene expression.
  • Novel components of GA signalling pathways could be used as targets for biotechnological modifications or marker assisted breeding.
  • Agrobiological compounds can be readily used in crop systems.
FUNDING
  • 2017-2019: Arabidopsis genes regulating seed germination and growth as targets to improve crop biomass and yield. MINECO (BIO2016-77840-R). PI: Luis Oñate-Sánchez.
  • 2014-2017: Studying gibberellin signalling to improve seed germination and resistance to stress. MINECO (BIO2013-46076-R). PI: Luis Oñate-Sánchez.
  • 2011-2014: Regulation of the hormonal balance controlling the transition between seed dormancy and germination. MICINN (BIO2010-17334) PI: Luis Oñate-Sánchez.
Representative Publications

Sánchez-Montesino, R; Oñate-Sánchez, L. 2017. "Yeast one- and two-hybrid high-throughput screenings using arrayed libraries", p. 47-65. In K. Kaufmann and B. Mueller-Roeber (eds.), Plant Gene Regulatory Networks: Methods and Protocols. Springer New York, New York, NY. DOI: 10.1007/978-1-4939-7125-1_5".

Ballester, P; Navarrete-Gómez, M; Carbonero, P; Oñate-Sánchez, L; Ferrándiz, C. 2015. "Leaf expansion in Arabidopsis is controlled by a TCP-NGA regulatory module likely conserved in distantly related species". Physiologia Plantarum. DOI: 10.1111/ppl.12327".

Thatcher, LF; Kamphuis, LG; Hane, JK; Oñate-Sánchez, L; Singh, KB. 2015. "The Arabidopsis KH-Domain RNA-Binding protein ESR1 functions in components of jasmonate signalling, unlinking growth restraint and resistance to stress". PLoS One. DOI: 10.1371/journal.pone.0126978".

Coego, A; Brizuela, E; Castillejo, P; Ruíz, S; Koncz, C; del Pozo, JC; Piñeiro, M; Jarillo, JA; Paz-Ares, J; León, J; Transplanta Consortium, T. 2014. "The TRANSPLANTA collection of Arabidopsis lines: a resource for functional analysis of transcription factors based on their conditional overexpression". Plant Journal. DOI: 10.1111/tpj.12443".

Rombolá-Caldentey, B; Rueda-Romero, P; Iglesias-Fernández, R; Carbonero, P; Oñate-Sánchez, L. 2014. "Arabidopsis DELLA and two HD-ZIP transcription factors regulate GA signaling in the epidermis through the L1 box cis-element". Plant Cell. DOI: 10.1105/tpc.114.127647".

Marin-de la Rosa, N; Sotillo, B; Miskolczi, P; Gibbs, DJ; Vicente, J; Carbonero, P; Onate-Sanchez, L; Holdsworth, MJ; Bhalerao, R; Alabadi, D; Blazquez, MA. 2014. "Large-scale identification of gibberellin-related transcription factors defines group VII ETHYLENE RESPONSE FACTORS as functional DELLA partners". Plant Physiology. DOI: 10.1104/pp.114.244723".

Iglesias-Fernández, R; Wozny, D; Iriondo-de Hond, M; Oñate-Sánchez, L; Carbonero, P; Barrero-Sicilia, C. 2014. "The AtCathB3 gene, encoding a cathepsin B-like protease, is expressed during germination of Arabidopsis thaliana and transcriptionally repressed by the basic leucine zipper protein GBF1". Journal of Experimental Botany. DOI: 10.1093/jxb/eru055".

Rueda-Romero P, Barrero-Sicilia C, Gómez-Cadenas A, Carbonero P and Oñate-Sánchez L* (2012) Arabidopsis thaliana DOF6 negatively affects germination in non-after-ripened seeds and interacts with TCP14. Journal of Experimental Botany 63: 1937-1949.

Iglesias-Fernández, R; Barrero-Sicilia, C; Carrillo-Barral, N; Oñate-Sánchez, L; Carbonero, P. 2013. "Arabidopsis thaliana bZIP44: a transcription factor affecting seed germination and expression of the mannanase encoding gene AtMAN7". Plant Journal. DOI: 10.1111/tpj.12162".

Castrillo G, Turck F, Leveugle M, Lecharny A, Carbonero P, Coupland G, Paz-Ares J and Oñate-Sánchez L* (2011) Speeding cis-trans regulation discovery by phylogenomic analyses coupled with screenings of an arrayed library of Arabidopsis transcription factors. PLoS ONE 6(6): e21524.

Wehner N, Hartmann L, Ehlert A, Böttner S, Oñate-Sánchez L and Dröge-Laser W (2011) High-throughput protoplast trans activation (PTA) system for the analysis of Arabidopsis transcription factor function. The Plant Journal 68: 560-569.

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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