Articles
Natural genetic diversity of barrel medic provides insight into the physiological bases of legume early seedling performance and plasticity to nitrate
Article number
1365_3
Pages
25 – 32
Language
English
Abstract
Abiotic stresses such as limited nitrogen availability can be challenging during the early stages of stand establishment.
Finding physiologically/metabolically N-efficient genotypes is critical in legumes where nitrate uptake and assimilation occur before nodulation.
We took advantage of barrel medic (Medicago truncatula) natural diversity (192 accessions) to identify markers associated with seedling performance with or without nitrate supply.
We determined traits associated with organ elongation and seed biomass during seedling heterotrophic growth and calculated indexes of plasticity to nitrate supply.
These indexes allowed us to group accessions into four nitrate response physiotypes.
A genome-wide association study (GWAS) identified loci associated with seedling performance and plasticity to nitrate.
In particular, we found one chromosomal region associated with seedling elongation that contained 16 genes encoding glutathione S-transferases (GSTs). This suggests the regulation of seedling elongation in absence of nitrate could be related to sulfur metabolism and/or control of oxidative stress.
A new phylogenetic classification of GST in M. truncatula showed that all GST genes associated with the locus belong to class Tau, a class known to be involved in abiotic stress responses and development.
Then, the monitoring of GST activity revealed a high positive relationship between hypocotyl and radicle length and GST activity during heterotrophic growth in the absence of nitrate, the correlation being strongest for hypocotyl elongation, known to be only driven by cell elongation.
Our findings suggest an interaction between GSTs and nitrate to control cell elongation during seedling heterotrophic growth.
They also suggest that nitrogen/sulfur metabolism appears to be a key player in the fitness of genotypes in response to nitrate availability.
Finding physiologically/metabolically N-efficient genotypes is critical in legumes where nitrate uptake and assimilation occur before nodulation.
We took advantage of barrel medic (Medicago truncatula) natural diversity (192 accessions) to identify markers associated with seedling performance with or without nitrate supply.
We determined traits associated with organ elongation and seed biomass during seedling heterotrophic growth and calculated indexes of plasticity to nitrate supply.
These indexes allowed us to group accessions into four nitrate response physiotypes.
A genome-wide association study (GWAS) identified loci associated with seedling performance and plasticity to nitrate.
In particular, we found one chromosomal region associated with seedling elongation that contained 16 genes encoding glutathione S-transferases (GSTs). This suggests the regulation of seedling elongation in absence of nitrate could be related to sulfur metabolism and/or control of oxidative stress.
A new phylogenetic classification of GST in M. truncatula showed that all GST genes associated with the locus belong to class Tau, a class known to be involved in abiotic stress responses and development.
Then, the monitoring of GST activity revealed a high positive relationship between hypocotyl and radicle length and GST activity during heterotrophic growth in the absence of nitrate, the correlation being strongest for hypocotyl elongation, known to be only driven by cell elongation.
Our findings suggest an interaction between GSTs and nitrate to control cell elongation during seedling heterotrophic growth.
They also suggest that nitrogen/sulfur metabolism appears to be a key player in the fitness of genotypes in response to nitrate availability.
Authors
D. Ben Hdech, C. Aubry, B. Alibert, D. Beucher, A.M. Limami, F. Montrichard, B. Teulat
Keywords
nitrate supply, heterotrophic growth, physiotypes, GWAS, gluthatione S-transferases
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