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Aperçu unusual locus S

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 Chantha SC(1), Herman AC(1,2), Castric V(3), Vekemans X(3), Marande W(4), Schoen DJ(1).

 Author information

(1) Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal, QC, Canada,H3A1B1.

(2) Department of Plant Biology, University of Minnesota, St Paul, MN, 55108, USA.

(3) Unité Evo-Eco-Paléo (EEP) - UMR 8198, CNRS/Université de Lille - Sciences et Technologies, Villeneuve d'Ascq Cedex, F-59655, France

(4) Institut National de la Recherche Agronomique, 31326, Castanet Tolosan Cedex, France. 

Journal: New Phytologist

DOI:   10.1111/nph.14764

 

Abstract

The Leavenworthia self-incompatibility locus (S locus) consists of paralogs (Lal2, SCRL) of the canonical Brassicaceae S locus genes (SRK, SCR), and is situated in a genomic position that differs from the ancestral one in the Brassicaceae. Unexpectedly, in a small number of Leavenworthia alabamica plants examined, sequences closely resembling exon 1 of SRK have been found, but the function of these has remained unclear. BAC cloning and expression analyses were employed to characterize these SRK-like sequences. An SRK-positive Bacterial Artificial Chromosome clone was found to contain complete SRK and SCR sequences located close by one another in the derived genomic position of the Leavenworthia S locus, and in place of the more typical Lal2 and SCRL sequences. These sequences are expressed in stigmas and anthers, respectively, and crossing data show that the SRK/SCR haplotype is functional in self-incompatibility. Population surveys indicate that < 5% of Leavenworthia S loci possess such alleles. An ancestral translocation or recombination event involving SRK/SCR and Lal2/SCRL likely occurred, together with neofunctionalization of Lal2/SCRL, and both haplotype groups now function as Leavenworthia S locus alleles. These findings suggest that S locus alleles can have distinctly different evolutionary origins.

 

Link: http://onlinelibrary.wiley.com/doi/10.1111/nph.14764/full

The cer-cqu gene cluster determines three key players in a beta-diketone synthase polyketide pathway synthesizing aliphatics in epicuticular waxes

Schneider LM, Adamski NM, Christensen CE, Stuart DB, Vautrin S, Hansson M, Uauy C, von Wettstein-Knowles P

Journal: Journal of Experimental Botany, 68

DOI: 5009-5009

Added on : 04 February 2018

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Schneider LM, Adamski NM, Christensen CE, Stuart DB, Vautrin S, Hansson M, Uauy C, von Wettstein-Knowles P

Journal: Journal of Experimental Botany, 68

DOI: 5009-5009

Abstract

Aliphatic compounds on plant surfaces, called epicuticular waxes, are the first line of defense against pathogens and pests, contribute to reducing water loss and determine other important phenotypes. Aliphatics can form crystals affecting light refraction, resulting in a color change and allowing identification of mutants in their synthesis or transport. The present study discloses three such Eceriferum (cer) genes in barley – Cer-c, Cer-q and Cer-u – known to be tightly linked and functioning in a biochemical pathway forming dominating amounts of β-diketone and hydroxy-β-diketones plus some esterified alkan-2-ols. These aliphatics are present in many Triticeae as well as dicotyledons such as Eucalyptus and Dianthus. Recently developed genomic resources and mapping populations in barley defined these genes to a small region on chromosome arm 2HS. Exploiting Cer-c and -u potential functions pinpointed five candidates, of which three were missing in apparent cer-cqu triple mutants. Sequencing more than 50 independent mutants for each gene confirmed their identification. Cer-c is a chalcone synthase-like polyketide synthase, designated diketone synthase (DKS), Cer-q is a lipase/carboxyl transferase and Cer-u is a P450 enzyme. All were highly expressed in pertinent leaf sheath tissue of wild type. A physical map revealed the order Cer-c, Cer-u, Cer-q with the flanking genes 101kb apart, confirming they are a gene cluster, Cer-cqu. Homology-based modeling suggests that many of the mutant alleles affect overall protein structure or specific active site residues. The rich diversity of identified mutations will facilitate future studies of three key enzymes involved in synthesis of plant apoplast waxes.

 

Link: https://academic.oup.com/jxb/article/67/9/2715/2877437

A bacterial artificial chromosome (bac) genomic approach reveals partial clustering of the furanocoumarin pathway genes in parsnip

Roselli S, Olry A, Vautrin S, Coriton O, Ritchie D, Galati G, Navrot N, Krieger C, Vialart G, Berges H, Bourgaud F, Hehn A

Journal: Plant Journal

DOI: 89: 1119-1132

Added on : 04 February 2018

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Roselli S, Olry A, Vautrin S, Coriton O, Ritchie D, Galati G, Navrot N, Krieger C, Vialart G, Berges H, Bourgaud F, Hehn A

Journal: Plant Journal

DOI: 89: 1119-1132

Abstract

Furanocoumarins are specialized metabolites that are involved in the defense of plants against phytophagous insects. The molecular and functional characterization of the genes involved in their biosynthetic pathway is only partially complete. Many recent reports have described gene clusters responsible for the biosynthesis of specialized metabolites in plants. To investigate possible co-localization of the genes involved in the furanocoumarin pathway, we sequenced parsnip BAC clones spanning two different gene loci. We found that two genes previously identified in this pathway, CYP71AJ3 and CYP71AJ4, were located on the same BAC, whereas a third gene, PsPT1, belonged to a different BAC clone. Chromosome mapping using fluorescence in situ hybridization (FISH) indicated that PsPT1 and the CYP71AJ3-CYP71AJ4 clusters are located on two different chromosomes. Sequencing the BAC clone harboring PsPT1 led to the identification of a gene encoding an Fe(II) α-ketoglutarate-dependent dioxygenase (PsDIOX) situated in the neighborhood of PsPT1 and confirmed the occurrence of a second gene cluster involved in the furanocoumarin pathway. This enzyme metabolizes p-coumaroyl CoA, leading exclusively to the synthesis of umbelliferone, an important intermediate compound in furanocoumarin synthesis. This work provides an insight into the genomic organization of genes from the furanocoumarin biosynthesis pathway organized in more than one gene cluster. It also confirms that the screening of a genomic library and the sequencing of BAC clones represent a valuable tool to identify genes involved in biosynthetic pathways dedicated to specialized metabolite synthesis.

Link: http://onlinelibrary.wiley.com/doi/10.1111/tpj.13450/abstract

Map-based cloning of the fertility restoration locus rfm1 in cultivated barley (hordeum vulgare)

Rizzolatti C, Bury P, Tatara E, Pin PA, Rodde N, Berges H, Budar F, Mireau H, Gielen JJL.

Journal: Euphytica

DOI: 213: 276.

Added on : 04 February 2018

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Rizzolatti C, Bury P, Tatara E, Pin PA, Rodde N, Berges H, Budar F, Mireau H, Gielen JJL.

Journal: Euphytica

DOI: 213: 276.

Abstract

Hybridization technology has proven valuable in enhancing yields in many crops, but was only recently adopted in the small grain cereals. Hybrid varieties in barley (Hordeum vulgare) rely on the cytoplasmic male sterility (CMS) system msm1 derived from Hordeum vulgare ssp. spontaneum. The major restorer gene described for the msm1 system is known as Rfm1 and maps to the top of chromosome 6H. To gain further insight into mechanisms underlying male fertility restoration in barley, we used a map-based cloning approach to identify the nuclear gene involved in the restoration mechanism of this hybridization system. Taking advantage of the available genomic resources in barley in combination with a custom-made non-gridded BAC library developed from a restorer line, we cloned and sequenced the Rfm1 restorer locus. The characterization and annotation of the nucleotide sequence for the Rfm1 restorer allele allowed for the identification of the candidate gene for Rfm1. The Rfm1 locus carries a tandem repeat of a gene encoding a pentatricopeptide repeat (PPR) protein. Surprisingly, Rfm1 belongs to the PLS-DYW subfamily of PPR genes known for their involvement in RNA editing in plants organelles, but that to date have not been identified as restorer genes.

 

Link: https://link.springer.com/article/10.1007%2Fs10681-017-2056-4