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Biological, physiological and molecular characterizations of desiccation of somatic and zygotic larch embryos. Analysis of the consequences in terms of seed quality.
Reference
1548916095
Deadline for applications
03/31/2019
Date of publication
01/31/2019

Details

Details on the type of contract
PhD contract
Duration of contract
3 years
Beginning
10/01/2019

Assignment

Name of unit of assignment
UMR0588 BioForA Biologie intégrée pour la valorisation de la diversité des Arbres et de la Forêt
Address of unit of assignment
INRA - 2163 avenue de la Pomme de Pin - CS 40001 Ardon - 45075 ORLEANS CEDEX 2
Region of assignment
Central France-Loire Valley

Description

Working environment

Reproduction is a key trait in forest trees population renewal (natural and/or artificial regeneration). Climate change (higher temperature, frequent drought) have a negative impact on the fructification of the trees, and then on seed production (Lebourgeois et al. 2010), which finally induces a limitation on seedling production. Vegetative multiplication could appear as an alternative to the lack of seedling. Among all the multiplication methods, somatic embryogenesis allows efficient multiplication of elite genotype obtained from the tree breeding programs (Lelu-Walter et al. 2013, 2016). However, somatic embryo at its final maturation stage is similar to a fresh zygotic embryo (seed embryo; Morel et al. 2014, Teyssier et al. 2014). Therefore, it does not reach the desiccated stage of a seed in the nature. This desiccation is characterized by many biochemical events come along with (accumulation of energy storage compounds) and a potential conservation of the seed. Seed quality is conditioned by its energy storage compounds (lipidic and proteic form), whereas its desiccation tolerance results from the presence of specific lipids and proteins.

  
The objective of this thesis is firstly to study physiological and molecular modifications involved in somatic embryo desiccation and the consequences on its quality through the germination ability. We propose biochemical and proteomic analysis in order to realize a qualitative and quantitative survey of the modifications occurring during somatic embryo desiccation. This study realized on somatic embryo, developed under controlled environmental conditions, will be then completed with a similar approach on seed in order to better understand its physiological and molecular developments during desiccation. Following this seed characterization using infrared spectroscopy, we should develop a calibration model that could allow predicting of seed quality.

  
Hence we should be able to suggest an alternative to seed diminution productivity that should define and encourage new practices to managers and operators of seed production structures. These studies will be conducted on larch, important species in French forests. Its breeding program is conducted in INRA Orleans that has also the expertise on its somatic embryogenesis (Lelu-Walter and Pâques 2009) and the desiccation treatment (Lelu et al. 1995, Dronne et al. 1997). This thesis will be associated to national and international research programs, and will include a mobility of the PhD student to the Botanic Experimental Institute (Prague, Czech Republic) in an internationally renowned laboratory for hormone analysis from conifer somatic embryogenesis. These are all important parameters that should guarantee the good conduct of this thesis and the production of results. The proposed studies will contribute to the acquisition of lacking knowledge
on conifers, where good quality seed production becomes a major goal for the future of our forests, and a sector that is head-on confronted to climate change.

Lebourgeois F, Rathgeber CBK, E Ulrich (2010) Sensitivity of French temperate coniferous forests to climate variability and extreme events (Abies alba, Picea abies and Pinus sylvestris). Journal of Vegetation Science 21, 364-376.
Dronne S, Label P, Lelu MA (1997) Desiccation decreases abscisic acid content in hybrid larch (Larix x leptoeuropaea) somatic embryos. Physiol. Plant. 99, 433-438.
Lelu M-A, Klimaszewska K, Pflaum G, Bastien C (1995). Effect of maturation duration on desiccation tolerance in hybrid larch (Larix x Leptoeuropaea dengler) somatic embryos. In Vitro Cellular & Developmental Biology - Plant, 31, 15-20.
Lelu-Walter M-A, Pâques L (2009). Simplified and improved somatic embryogenesis of hybrid larches (Larix x eurolepis and Larix x marschlinsii). Perspectives for breeding. Annals of Forest Science, 66, 104.
Lelu-Walter M-A, Thompson D, Harvengt L, Sanchez L, Toribio M, Pâques LE (2013) Somatic embryogenesis in forestry with a focus on Europe: state-of-the-art, benefits, challenges and future direction. Tree Genet Genomes, 9, 883-899.
Lelu-Walter M-A, Teyssier C, Guérin V, Pâques LE (2016) Vegetative propagation of larch species: somatic embryogenesis improvement towards its integration in breeding programs. Dans: Park Y-S, Bonga JM, Moon H-K (éds) Vegetative Propagation of Forest Trees. National Institute of Forest Science (NIFoS). Seoul, Korea, pp 551-571.
Morel A, Trontin JF, Corbineau F, Lomenech A-M, Beaufour M, Reymond I, Le Metté C, Ader K, Harvengt L, Cadene M, Label P, Teyssier C, Lelu-Walter, M-A (2014) Cotyledonary somatic embryos of Pinus pinaster Ait. most closely resemble fresh, maturing cotyledonary zygotic embryos: biological, carbohydrate and proteomic analyses. Planta, 240, 1075-1095.
Teyssier C, Maury S, Beaufour M, Grondin C, Delaunay A, Le Metté C, Ader K, Cadene M, Label P, Lelu-Walter M-A (2014) In search of markers for somatic embryo maturation in hybrid larch (Larix x eurolepis): global DNA methylation and proteomic analyses. Physiol Plant 150, 271-291.

Training and skills required

Etudiant(e), détenteur d’un master 2 (à la date prise de fonction), doit avoir solides connaissances en
Biologie/physiologie végétales, et avec de bonnes connaissances en biologie cellulaire,
embryogenèse et en biologie moléculaire.

Contact

Name
LELU-WALTER Marie-Anne / TEYSSIER Caroline
Email
marie-anne.lelu-walter@inra.fr ; Caroline.Teyssier@inra.fr