H2020 ROOT BARRIERS Project: Molecular mechanisms controlling endodermis and exodermis differentiation in tomato roots
- Type Project
- Status Filled
- Execution 2016 -2019
- Assigned Budget 239.191,2 €
- Scope Europeo
- Main source of financing H2020
- Project website ROOT BARRIERS
The world's population is expected to reach 11.2 billion by 2100. With looming climate change, water and food security have become one of the greatest challenges humanity will face in the near future. In this context, agriculture, as the primary source of food for humans and animals, is of particular importance. It is urgent to improve and create more resilient crops that can grow under water-scarce conditions. The genetic study of plant species that have evolved and naturally adapted to arid environments provides a source of knowledge to meet this need. In plants, the root system is responsible for absorbing water and nutrients from the soil. When environmental conditions are adverse, such as drought, the roots must respond to them. There are specific cell types in the plant root, the endodermis and exodermis, which, when differentiated, form barriers that help cope with these adverse conditions. However, to date, the molecular factors that control exodermal differentiation, as well as whether the regulatory mechanisms determining their development are the same or distinct, remain unknown. The ROOT BARRIERS project has addressed these questions by studying the differentiation of the endodermis and exodermis in tomato, a plant species that develops both layers. We have studied the differentiation of the exodermis and endodermis using the domesticated species Solanum lycopersicum 'M82' and the wild Solanum pennellii, as they have different root morphology and cell development, and we have found that they differ in their differentiation characteristics. Furthermore, our results suggest that the differentiation of the endodermis and exodermis in tomato does not share the same molecular regulators. Some studies have revealed that the differentiation of the endodermis and exodermis occurs early in response to salt stress. The ROOT BARRIERS project aimed to study how salt stress affects the differentiation of the endodermis and exodermis in tomato roots, also using S. lycopersicum 'M82' and S. pennellii. Furthermore, the role of these two cell types is of particular interest since S. pennellii is a salinity-tolerant species, suggesting that the environment can directly regulate the development of a specific cell type. We have generated stable transgenic plants to isolate messenger RNA specifically from the endodermis and exodermis under control and salt stress conditions. In this way, we will be able to identify the regulators involved in the differentiation of these two cell types and how salt stress influences the control of their differentiation at the molecular level.
Work carried out since the beginning of the project
- Expression pattern of the SlCASPs, SlSGN3, SlCIF2, SlMYB36 genes in the tomato root.
- Localization of SlCASP proteins in the tomato root.
- Developmental framework for endodermis and exodermis differentiation in Solanum lycopersicum and Solanum pennelli under control and salt stress conditions.
- Identification of an exodermis-specific promoter.
- Generation of INTACT and TRAP lines to profile mRNA of the endodermis and exodermis in Solanum lycopersicum and Solanum pennelli.
- Testing the apoplastic pathway in the exodermis and endodermis using specific tracers.
- CRISPR mutants for candidate genes potentially involved in endodermal and exodermal differentiation.
- Transcription profile of endodermis and exodermis under control and salt stress conditions.
Results obtained - There are different developmental frameworks for the differentiation of the endodermis and exodermis in tomato.
- None of the Arabidopsis molecular players that control endodermal differentiation, homologous to tomato, show a specific expression pattern in the endodermis or exodermis, as they are at least expressed in both. Some of them are also expressed in cells of the cortex and epidermis.
- We have identified an exodermal-specific promoter. We will be able to specifically profile the mRNA of exodermal cells using the INTACT and TRAP protocols.
- Salt stress is differentially affecting root development and the differentiation of the endodermis and exodermis in Solanum lycopersicum and Solanum pennelli.
- The tomato exodermis shows a plastic response in the formation of apoplastic barriers under salt stress conditions.
Exploitation and dissemination of results
The results of the Root Barriers project were presented at the following conferences: - Poster presentation. 8th International Symposium on Root Development. Umea (Sweden, 2017)
- Poster presentation. FASEB Meeting. Vermont, USA (2017)
- Oral presentation. Plant development and water stress. Asilomar (USA) (2017)
- Poster presentation. 14th Plant Molecular Biology Meeting. Salamanca (Spain) (2018).
- Poster presentation. 10th ISRR International Symposium. Israel (2018)
The world's population is expected to reach 11.2 billion by 2100. With looming climate change, water and food security has become one of the greatest challenges humanity will face in the near future. In this context, agriculture, as the primary source of food for humans and animals, is of particular importance. It is urgent to improve and develop more resilient crops that can grow under water-scarce conditions.
The genetic study of plant species that have evolved and naturally adapted to arid environments provides a source of knowledge to meet this need. In plants, the root system is responsible for absorbing water and nutrients from the soil. When environmental conditions are adverse, such as drought, the roots must respond. There are specific cell types in the plant root, the endodermis and exodermis, which, when differentiated, form barriers that help cope with these adverse conditions.
However, to date, the molecular factors that control the differentiation of the exodermis remain unknown, as well as whether the regulatory mechanisms that determine its development are the same or different.
The ROOT BARRIERS project has addressed these questions by studying the differentiation of the endodermis and exodermis in tomato, a plant species that develops both layers. We have studied the differentiation of the exodermis and endodermis using the domesticated species Solanum lycopersicum 'M82' and the wild Solanum pennellii, as they have different root morphologies and cell development, and we have found that they differ in their differentiation characteristics.
Furthermore, our results suggest that the differentiation of the endodermis and exodermis in tomato does not share the same molecular regulators. Some studies have shown that the differentiation of the endodermis and exodermis occurs early in response to salt stress.
The ROOT BARRIERS project aimed to study how salt stress affects the differentiation of the endodermis and exodermis in tomato roots, also using S. lycopersicum 'M82' and S. pennellii. Furthermore, the role of these two cell types is of particular interest since S. pennellii is a salinity-tolerant species, suggesting that the environment can directly regulate the development of a specific cell type. We have generated stable transgenic plants to isolate messenger RNA specifically from the endodermis and exodermis under control and salt stress conditions. In this way, we will be able to identify the regulators involved in the differentiation of these two cell types and how salt stress influences the control of their differentiation at the molecular level.
The root system anchors the plant, and its cells absorb water and nutrients. Since plants are sessile organisms, controlling the entry of external compounds is essential for their survival. In vascular plants, the endodermis is the innermost cellular layer of the root's ground tissue, which controls entry into the plant vasculature by forming a barrier to the free diffusion of solutes from the soil. In addition, many plant species also contain a layer of exodermis, which also acts as a barrier. The exodermis is located internal to the epidermis layer.
In a differentiated state, cells in both layers contain a Casparian band. In Arabidopsis, the Casparian band is a lignin-like structure deposited as a ring in the cross-section of cells and around the secondary cell wall. Recently, the developmental framework for endodermal differentiation in Arabidopsis has been described, and several important molecular players have been identified.
Here, we explore whether endodermal and exodermal differentiation are regulated similarly. Since Arabidopsis lacks an exodermis, the proposed project will use the tomato root as a model system to address endodermal and exodermal differentiation at the phenotypic and molecular levels. Furthermore, differences between species growing in environments similar to the one to which they have adapted will be analyzed.
To address this problem, newly developed tools and technologies will be used to obtain a cell-type-specific transcriptome from the tomato root, as well as the data analysis necessary for systems biology and genomic approaches. The proposed project will provide new insights into the development of the endodermis and exodermis in tomato at the phenotypic and molecular levels, and will lay the groundwork for its study in other plant species.
To date, the molecular mechanism controlling exodermis differentiation is unknown, as the model organism Arabidopsis thaliana does not form one. The endodermis and exodermis form barriers that control the entry of water and solutes from the soil.
With the ROOT BARRIERS project, using tomato as a model system, we will describe for the first time whether the molecular factors that control the differentiation of the endodermis and exodermis are the same or distinct. Furthermore, we are studying two tomato species that differ in their adaptability to drought. Comparing the response of the endodermis and exodermis to saline conditions in these two species will allow us to elucidate whether a differential response in these cell types mediates their different tolerance to water stress. Elucidating the genes that control the formation of these barriers will help us modulate root response under stress conditions such as drought and salinity.
The long-term socioeconomic impact of this project will be based on the development of more resilient crops that can grow under drought conditions, as an increase in desert areas is expected with impending climate change.
- CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS (CSIC)
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