title: Silencing of flavanone-3-hydroxylase in apple (Malus × domestica Borkh.) leads to accumulation of flavanones, but not to reduced fire blight susceptibility.
abstract: Transgenic antisense flavanone-3-hydroxylase apple plants were produced to mimic the effect of the agrochemical prohexadione-Ca on apple leaves. This enzyme inhibitor for 2-oxoglutarate dependent dioxygenases is used as a growth retardant and for control of secondary fire blight of leaves. Like using the agent, silencing of flavanone-3-hydroxylase leads to an accumulation of flavanones in leaves, but in contrast not to the formation of 3-deoxyflavonoids. In prohexadione-Ca treated leaves the 3-deoxyflavonoid luteoforol is formed from accumulating flavanones, acting as an antimicrobial compound against the fire blight pathogen Erwinia amylovora. Seemingly, the silencing of just one of the 2-oxoglutarate dependent dioxygenases (in apple also flavonol synthase and anthocyanidin synthase take part downstream in the pathway) does not provide a sufficiently high ratio of flavanones to dihydroflavonols. This seems to be needed to let the dihydroflavonol-4-reductase/flavanone-4-reductase enzyme reduce flavanones to luteoforol, and to let this be reduced by the leucoanthocyanidin-4-reductase/3-deoxyleucoanthocyanidin-4-reductase, each acting with their respective weak secondary activities. Accordingly, also the intended inducible resistance to fire blight by prohexadione-Ca is not observed with the antisense flavanone-3-hydroxylase apple plants. On the other hand, for most transgenic lines with strong flavanone-4-reductase down-regulation, up-regulation of gene expression for the other flavonoid genes was found. This provides further evidence for the feedback regulation of flavonoid gene expression having been previously reported for the prohexadione-Ca inhibited apple plants.
authors.affiliation: Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Fruit Breeding, Dresden, Germany. henryk.flachowsky@jki.bund.de
authors.forename: Henryk
authors.initials: H
authors.lastname: Flachowsky
authors.forename: Heidi
authors.initials: H
authors.lastname: Halbwirth
authors.forename: Dieter
authors.initials: D
authors.lastname: Treutter
authors.forename: Klaus
authors.initials: K
authors.lastname: Richter
authors.forename: Magda-Viola
authors.initials: MV
authors.lastname: Hanke
authors.forename: Iris
authors.initials: I
authors.lastname: Szankowski
authors.forename: Christian
authors.initials: C
authors.lastname: Gosch
authors.forename: Karl
authors.initials: K
authors.lastname: Stich
authors.forename: Thilo C
authors.initials: TC
authors.lastname: Fischer
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology; D001578:Benzopyrans / Q000378:metabolism / Q000494:pharmacology; D003001:Cloning, Molecular; D003470:Culture Media / Q000378:metabolism; D004198:Disease Susceptibility / Q000276:immunology / Q000382:microbiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044084:Erwinia amylovora / Q000187:drug effects / Q000276:immunology / Q000472:pathogenicity; D044950:Flavanones / Q000096:biosynthesis* / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000494:pharmacology; D027845:Malus / Q000201:enzymology / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D018520:Plant Shoots / Q000201:enzymology / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D000900:Anti-Bacterial Agents; D001578:Benzopyrans; D003470:Culture Media; D004791:Enzyme Inhibitors; D044950:Flavanones; D007656:Ketoglutaric Acids; D010940:Plant Proteins; C479018:prohexadione-Ca; C431922:luteoforol; D006899:Mixed Function Oxygenases; D000429:Alcohol Oxidoreductases; C056570:dihydroflavanol 4-reductase; C048797:flavanone 3-dioxygenase