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Management of nitrogen and crops productivity
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Keywords : Assimilation, nitrogen, mobilization, circadian rhythm, quantitative genetics, grain, phloem

Doctoral school affiliation : ED 145 Sciences du végétal,Université Paris-Sud 11, Orsay

Contacts :

Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech
Bâtiment 2
INRA Centre de Versailles-Grignon
Route de St-Cyr (RD10)
78026 Versailles Cedex France

tél : +33 (0)1 30 83 30 00 - fax : +33 (0)1 30 83 33 19

Group leader
Bertrand Hirel
Senior Scientist CNRS


Estelle Wenes
Engineer

Marien Havé
Contractual Engineer

Isabelle

Isabelle Quilleré-Ducher
Engineer

Patrick

Lenaïg Guillard
Technician

 

 


Summary :

Our overall objective is to better understand and improve nitrogen use efficiency (NUE: Nitrogen Use Efficiency) in maize and wheat. Indeed these two plants, which represent with rice the main food and feed supply in the world, require significant inputs of nitrogen fertilizer (especially nitrogen) to obtain optimum yield. Improving NUE is a major challenge, considering the growing demand for agricultural products of the world's population, the rising cost of fossil fuels needed for the production of nitrogen fertilizers and the water pollution caused by the application of excess nitrate to cultivated lands. Therefore, it is necessary to select new varieties of maize and wheat, less demanding in nitrogen fertilization (20 to 30% less), with both high productivity and good grain quality (protein content, in particular).


Main Results :

In recent years, studies have been undertaken to identify the limiting steps of the absorption, assimilation and recycling of nitrogen during plant growth and development in general and in cereals in particular. Our team has made significant progress in understanding the mechanisms of assimilation and recycling of nitrogen during vegetative growth and during the grain filling period. This work was conducted in collaboration with agronomists and geneticists in the public sector at the National Institute of Agronomic Research (INRA; http://www.inra.fr/), and with our private partner (BIOGEMMA; http:/ / www.biogemma.com/) through the program GENOPLANTE (http://www.genoplante.com/). We have developed a multidisciplinary approach combining molecular physiology and agronomy to study in an integrated manner the regulation of plant nitrogen management. These include the absorption of nitrogen before and after flowering and its remobilization to the grain after pollination. Our group has also developed a quantitative genetics approach (with Prof. A. Gallais at the INRA / CNRS. University of Paris XI, the UMR Plant Genetics, the Farm Moulon, Gif sur Yvette, Http: // moulon. inra.fr/SGVGQMS/ GQMS.html) to identify key genes involved in the regulation of nitrogen management and to exploit the genetic variability for selecting new varieties with improved NUE. A search for QTLs (Quantitative Trait Loci) has been undertaken to associate agronomic performance with metabolic functions related to the absorption of nitrogen on a maize genetic map. Finding co-localisations between QTLs for yield and their components and genes encoding cytosolic glutamine synthetase (GS1) has been one of the most significant outcomes of this study. We have established that GS1 controls one of the limiting steps in maize kernel production, since kernel number was strongly reduced in mutants deficient in GS1 and increased in plants overexpressing the enzyme. We are currently searching for other candidate genes involved in the control of NUE in maize and wheat by combining transcriptome, proteome and whole plant physiology approaches.

Under nitrogen suboptimal conditions (N+) a mutant deficient for the cytosolic GS isoenzyme GS1-4 (gln1-4) exhibits a reduction of kernel size compared to the wild type (WT) whereas in a mutant deficient for GS1-3 (gln1-3) there is a reduction of kernel number. In the gln1-3/1-4 doublemutanta cumulative effect of the two mutations was observed. Under nitrogen deficient conditions (N-) the ear of the WT exhibits a severe reduction in kernel number, whereas the three mutants did not produce any kernels. This observation suggests that GS1-4 and GS1-3 control grain yield in maize whatever the level of nitrogen fertilisation.

 

 


Selected Publications :

Gallais A, Coque M, Quilleré I, Le Gouis J, Prioul JL, Hirel B (2007) Estimating proportions of N remobilization and of post-silking N uptake allocated to maize kernels by 15N labelling. Crop Sci, 47: 685-691.

Kichey T, Hirel B, Heumez E, Dubois F, Le Gouis J (2007) Wheat genetic variability for post-anthesis nitrogen absorption and remobilisation revealed by 15N labelling and correlations with agronomic traits and nitrogen physiological markers. Field Crop Res, 102 : 22-32.

Hirel B, Le Gouis J, Ney B, Gallais A. (2007) The challenge of improving nitrogen use efficiency in crop plants : towards a more central role for genetic variability and quantitative genetics within integrated approaches. J Exp Bot, 58 : 2369-2387

Martin A, Lee J, Kichey T,  Gerentes D, Zivy M, Tatou C, Balliau, Valot B, Davanture M, Dubois F, Tercé-Laforgue T, Coque M, Gallais A, Gonzales-Moro MB, Bethencourt L, Quilleré I, Habash DZ, LEA PJ, Charcosset A, Perez P, Murigneux A, Sakakibara H, Edwards KJ, Hirel B (2006) Two cytosolic glutamine synthetase isoforms of maize (Zea mays L.) are specifically involved in the control of grain production. The Plant Cell, 18 : 3252-3274.

Tercé-Laforgue T, Dubois F, Ferrario-Mery S, Pou de Crecenzo MA, Sangwan ., Hirel B (2004) Glutamate dehydrogenase of tobacco (Nicotiana tabacum L.) is mainly induced in the cytosol of phloem companion cells when ammonia is provided either externally or released during photorespiration. Plant Physiol, 136 : 4308-4317.

 

 

 

 

 


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