Construction of chromosome segment substitution lines in peanut (Arachis hypogaea L.) using a wild synthetic and QTL mapping for plant morphology

Chromosome segment substitution lines (CSSLs) are powerful QTL mapping populations that have been used to elucidate the molecular basis of interesting traits of wild species. Cultivated peanut is an allotetraploid with limited genetic diversity. Capturing the genetic diversity from peanut wild relatives is an important objective in many peanut breeding programs. In this study, we used a marker-assisted backcrossing strategy to produce a population of 122 CSSLs from the cross between the wild synthetic allotetraploid (A. ipae¨nsis6A. duranensis)4x and the cultivated Fleur11 variety. The 122 CSSLs offered a broad coverage of the peanut genome, with target wild chromosome segments averaging 39.2 cM in length. As a demonstration of the utility of these lines, four traits were evaluated in a subset of 80 CSSLs. A total of 28 lines showed significant differences from Fleur11. The line6trait significant associations were assigned to 42 QTLs: 14 for plant growth habit, 15 for height of the main stem, 12 for plant spread and one for flower color. Among the 42 QTLs, 37 were assigned to genomic regions and three QTL positions were considered putative. One important finding arising from this QTL analysis is that peanut growth habit is a complex trait that is governed by several QTLs with different effects. The CSSL population developed in this study has proved efficient for deciphering the molecular basis of trait variations and will be useful to the peanut scientific community for future QTL mapping studies. (Résumé d'auteur

Complex regulation of two target genes encoding SPX-MFS proteins by rice miR827 in response to phosphate starvation.

Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’ ‘Team AFFS Architecture and Functioning of Fruit Species’ Contact: [email protected], [email protected] audienceHere we report on the characterization of rice osa-miR827 and its two target genes, OsSPX-MFS1 and OsSPX-MFS2, which encode SPX-MFS proteins predicted to be implicated in phosphate (Pi) sensing or transport. We first show by Northern blot analysis that osa-miR827 is strongly induced by Pi starvation in both shoots and roots. Hybridization of osa-miR827 in situ confirms its strong induction by Pi starvation, with signals concentrated in mesophyll, epidermis and ground tissues of roots. In parallel, we analyzed the responses of the two OsSPX-MFS1 and OsSPX-MFS2 gene targets to Pi starvation. OsSPX-MFS1 mRNA is mainly expressed in shoots under sufficient Pi supply while its expression is reduced on Pi starvation, revealing a direct relationship between induction of osa-miR827 and down-regulation of OsSPX-MFS1. In contrast, OsSPX-MFS2 responds in a diametrically opposed manner to Pi starvation. The accumulation of OsSPX-MFS2 mRNA is dramatically enhanced under Pi starvation, suggesting the involvement of complex regulation of osa-miR827 and its two target genes. We further produced transgenic rice lines overexpressing osa-miR827 and T-DNA knockout mutant lines in which the expression of osa-miR827 is abolished. Compared with wild-type controls, both target mRNAs exhibit similar changes, their expression being reduced and increased in overexpressing and knockout lines, respectively. This suggests that OsSPX-MFS1 and OsSPX-MFS2 are both negatively regulated by osa-miR827 abundance although they respond differently to external Pi conditions. We propose that this is a complex mechanism comprising fine tuning of spatial or temporal regulation of both targets by osa-miR827

Construction of Chromosome Segment Substitution Lines in Peanut (Arachis hypogaea L.) Using a Wild Synthetic and QTL Mapping for Plant Morphology

Abstract Chromosome segment substitution lines (CSSLs) are powerful QTL mapping populations that have been used to elucidate the molecular basis of interesting traits of wild species. Cultivated peanut is an allotetraploid with limited genetic diversity. Capturing the genetic diversity from peanut wild relatives is an important objective in many peanut breeding programs. In this study, we used a marker-assisted backcrossing strategy to produce a population of 122 CSSLs from the cross between the wild synthetic allotetraploid (A. ipaënsis6A. duranensis) 4x and the cultivated Fleur11 variety. The 122 CSSLs offered a broad coverage of the peanut genome, with target wild chromosome segments averaging 39.2 cM in length. As a demonstration of the utility of these lines, four traits were evaluated in a subset of 80 CSSLs. A total of 28 lines showed significant differences from Fleur11. The line6trait significant associations were assigned to 42 QTLs: 14 for plant growth habit, 15 for height of the main stem, 12 for plant spread and one for flower color. Among the 42 QTLs, 37 were assigned to genomic regions and three QTL positions were considered putative. One important finding arising from this QTL analysis is that peanut growth habit is a complex trait that is governed by several QTLs with different effects. The CSSL population developed in this study has proved efficient for deciphering the molecular basis of trait variations and will be useful to the peanut scientific community for future QTL mapping studies

Evolution of donor and recurrent genome representation during the development of the CSSL population.

<p>Evolution of donor and recurrent genome representation during the development of the CSSL population.</p

Selected morphological characteristics of the parents.

<p>Selected morphological characteristics of the parents.</p

Variation and descriptive statistics of the traits measured in the CSSL population and the recurrent parent.

<p>Variation and descriptive statistics of the traits measured in the CSSL population and the recurrent parent.</p

Graphical genotypes of the 80 CSSLs, highlighting significant lines×traits significant association and QTL positions.

<p>Graphical genotypes are represented in the same way as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048642#pone-0048642-g003" target="_blank">Figure 3</a>. Lines showing significant differences from Fleur11 are highlighted in orange. Relative line effects for each trait are depicted as circles on the right of the graphic. The size of each circle is proportional to its relative effect. Horizontal bars at the bottom of the graphic indicate deduced QTL positions. The colors of the circles and bars represent the direction of the effect. Red = increasing effect, green = decreasing effect.</p

Significant line×trait associations observed in the CSSL population.

<p>The values for GH (growth habit), PH (plant height) and PS (plant spread) represent the differences between the CSSL line and Fleur11, relative to the value of Fleur11. For the categorical trait YF (flower color), the value 1 corresponds to the yellow flower phenotype. Plant nb: number of plants measured. Chromosome: chromosome carrying the target segment.</p