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1.
Plant J ; 119(1): 364-382, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38652034

RESUMO

Barley produces several specialized metabolites, including five α-, ß-, and γ-hydroxynitrile glucosides (HNGs). In malting barley, presence of the α-HNG epiheterodendrin gives rise to undesired formation of ethyl carbamate in the beverage production, especially after distilling. Metabolite-GWAS identified QTLs and underlying gene candidates possibly involved in the control of the relative and absolute content of HNGs, including an undescribed MATE transporter. By screening 325 genetically diverse barley accessions, we discovered three H. vulgare ssp. spontaneum (wild barley) lines with drastic changes in the relative ratios of the five HNGs. Knock-out (KO)-lines, isolated from the barley FIND-IT resource and each lacking one of the functional HNG biosynthetic genes (CYP79A12, CYP71C103, CYP71C113, CYP71U5, UGT85F22 and UGT85F23) showed unprecedented changes in HNG ratios enabling assignment of specific and mutually dependent catalytic functions to the biosynthetic enzymes involved. The highly similar relative ratios between the five HNGs found across wild and domesticated barley accessions indicate assembly of the HNG biosynthetic enzymes in a metabolon, the functional output of which was reconfigured in the absence of a single protein component. The absence or altered ratios of the five HNGs in the KO-lines did not change susceptibility to the fungal phytopathogen Pyrenophora teres causing net blotch. The study provides a deeper understanding of the organization of HNG biosynthesis in barley and identifies a novel, single gene HNG-0 line in an elite spring barley background for direct use in breeding of malting barley, eliminating HNGs as a source of ethyl carbamate formation in whisky production.


Assuntos
Glucosídeos , Hordeum , Hordeum/genética , Hordeum/metabolismo , Hordeum/microbiologia , Glucosídeos/metabolismo , Nitrilas/metabolismo , Locos de Características Quantitativas , Uretana/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Estudo de Associação Genômica Ampla
2.
Trends Plant Sci ; 19(10): 656-63, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25017701

RESUMO

Overexpression of the cytosolic enzyme glutamine synthetase 1 (GS1) has been investigated in numerous cases with the goal of improving crop nitrogen use efficiency. However, the outcome has generally been inconsistent. Here, we review possible reasons underlying the lack of success and conclude that GS1 activity may be downregulated via a chain of processes elicited by metabolic imbalances and environmental constraints. We suggest that a pivotal role of GS1 may be related to the maintenance of essential nitrogen (N) flows and internal N sensing during critical stages of plant development. A number of more refined overexpression strategies exploiting gene stacking combined with tissue and cell specific targeting to overcome metabolic bottlenecks are considered along with their potential in relation to new N management strategies.


Assuntos
Regulação Enzimológica da Expressão Gênica , Glutamato-Amônia Ligase/metabolismo , Nitrogênio/metabolismo , Produtos Agrícolas , Citosol/enzimologia , Expressão Gênica , Regulação da Expressão Gênica de Plantas , Glutamato-Amônia Ligase/genética , Fenótipo , Folhas de Planta/genética , Folhas de Planta/metabolismo , Plantas Geneticamente Modificadas
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