Lipoxygenase(LOX)is an important contributor to the formation of aroma-active C6 aldehydes in apple(Malus×domestica)fruit upon tissue disruption but little is known about its role in autonomously produced aroma v...Lipoxygenase(LOX)is an important contributor to the formation of aroma-active C6 aldehydes in apple(Malus×domestica)fruit upon tissue disruption but little is known about its role in autonomously produced aroma volatiles from intact tissue.We explored the expression of 22 putative LOX genes in apple throughout ripening,but only six LOXs were expressed in a ripening-dependent manner.Recombinant LOX1:Md:1a,LOX1:Md:1c,LOX2:Md:2a and LOX2:Md:2b proteins showed 13/9-LOX,9-LOX,13/9-LOX and 13-LOX activity with linoleic acid,respectively.While products of LOX1:Md:1c and LOX2:Md:2b were S-configured,LOX1:Md:1a and LOX2:Md:2a formed 13(R)-hydroperoxides as major products.Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation.The high expression level of the corresponding MdLOX1a gene in stored apple fruit,the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio-and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits,suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples.While LOX1:Md:1c,LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.展开更多
The abundance of predatory phytoseiid mites,Typhlodromus pyri,important biological control agents of spider mite pests in numerous crops,is positively influenced by the density of leaf trichomes and tuft-form domatia ...The abundance of predatory phytoseiid mites,Typhlodromus pyri,important biological control agents of spider mite pests in numerous crops,is positively influenced by the density of leaf trichomes and tuft-form domatia in vein axils.Identification of the genetic regions controlling both trophic levels could facilitate the improvement of predatory mite habitat in breeding programs.The abundance of T.pyri and non-glandular trichomes was measured in a segregating F1 family derived from the cross of the complex Vitis hybrid,‘Horizon’,with Illinois 547-1(V.rupestris B38×V.cinerea B9),finding positive correlation among traits.High density genetic maps were used to localize one major quantitative trait locus(QTL)on chromosome 1 of Illinois 547-1 associated with both predatory mite abundance and leaf trichomes.This QTL explained 23%of the variation in phytoseiid abundance and similar amounts of variance in domatia rating(21%),domatia size(16%),leaf bristle density(37%in veins and 33%in blades),and leaf hair density(20%in veins and 15%in blades).Another nine QTL distributed among chromosomes 1,2,5,8,and 15 were associated solely with trichome density,and explained 7–17%of the phenotypic variation.Combined,our results provide evidence of the genetic architecture of non-glandular trichomes in Vitis,with a major locus influencing trichome densities,domatia size and predatory mite abundance.This information is relevant for breeding grapevines with a more favorable habitat for biological control agents.展开更多
基金This research was financially supported by the Deutsche Forschungsgemeinschaft in frame of the project numbers AOBJ 575560 and AOBJ 575561.
文摘Lipoxygenase(LOX)is an important contributor to the formation of aroma-active C6 aldehydes in apple(Malus×domestica)fruit upon tissue disruption but little is known about its role in autonomously produced aroma volatiles from intact tissue.We explored the expression of 22 putative LOX genes in apple throughout ripening,but only six LOXs were expressed in a ripening-dependent manner.Recombinant LOX1:Md:1a,LOX1:Md:1c,LOX2:Md:2a and LOX2:Md:2b proteins showed 13/9-LOX,9-LOX,13/9-LOX and 13-LOX activity with linoleic acid,respectively.While products of LOX1:Md:1c and LOX2:Md:2b were S-configured,LOX1:Md:1a and LOX2:Md:2a formed 13(R)-hydroperoxides as major products.Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation.The high expression level of the corresponding MdLOX1a gene in stored apple fruit,the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio-and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits,suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples.While LOX1:Md:1c,LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.
基金supported by the Specialty Crop Research Initiative of the National Institute of Food and Agriculture,U.S.Department of Agriculture,under award number 2011-51181-30635 and National Research Initiative award number 2004-35302-14725.
文摘The abundance of predatory phytoseiid mites,Typhlodromus pyri,important biological control agents of spider mite pests in numerous crops,is positively influenced by the density of leaf trichomes and tuft-form domatia in vein axils.Identification of the genetic regions controlling both trophic levels could facilitate the improvement of predatory mite habitat in breeding programs.The abundance of T.pyri and non-glandular trichomes was measured in a segregating F1 family derived from the cross of the complex Vitis hybrid,‘Horizon’,with Illinois 547-1(V.rupestris B38×V.cinerea B9),finding positive correlation among traits.High density genetic maps were used to localize one major quantitative trait locus(QTL)on chromosome 1 of Illinois 547-1 associated with both predatory mite abundance and leaf trichomes.This QTL explained 23%of the variation in phytoseiid abundance and similar amounts of variance in domatia rating(21%),domatia size(16%),leaf bristle density(37%in veins and 33%in blades),and leaf hair density(20%in veins and 15%in blades).Another nine QTL distributed among chromosomes 1,2,5,8,and 15 were associated solely with trichome density,and explained 7–17%of the phenotypic variation.Combined,our results provide evidence of the genetic architecture of non-glandular trichomes in Vitis,with a major locus influencing trichome densities,domatia size and predatory mite abundance.This information is relevant for breeding grapevines with a more favorable habitat for biological control agents.