The strawberry fruit Fra a allergen functions in flavonoid biosynthesis.
The strawberry Fra a 1 allergen is a homolog of the major birch pollen allergen Bet v 1. It is synthesized by red ripe fruits of Fragaria x ananassa while white fruits of a mutant genotype, which is known to be tolerated by individuals affected by allergy, are devoid of it. Proteomic analyses have shown that Fra a 1 is down-regulated in the tolerated white-fruited genotype along with enzymes of the anthocyanin pigment pathway. In this study, we report the spatial and temporal expression of three Fra a genes that encode different isoforms, and the transient RNAi-mediated silencing of the Fra a genes in strawberry fruits of the red-fruited cultivar Elsanta with an ihpRNA construct. As a consequence of reduced levels of Fra a mRNAs, fruits were obtained that produced significantly decreased levels of anthocyanins and upstream metabolites. This effect is consistent with the parallel down-regulation of the phenylalanine ammonia lyase (FaPAL) and to a lesser extent of the chalcone synthase (FaCHS) transcript levels also found in these fruits. In naturally occurring white-fruited genotypes of F. chiloensis and F. vesca, Fra a transcript levels are higher than those of the red-fruited varieties, likely to compensate for the low expression levels of FaPAL and FaCHS in these mutant genotypes. The results demonstrate that Fra a expression is directly linked to flavonoid biosynthesis and show that the Fra a allergen has an essential biological function in pigment formation in strawberry fruit.
Muñoz
Cristina
C
Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, Málaga, Spain.
Hoffmann
Thomas
T
Escobar
Nieves Medina
NM
Ludemann
Felix
F
Botella
Miguel A
MA
Valpuesta
Victoriano
V
Schwab
Wilfried
W
D000485:Allergens / Q000235:genetics / Q000378:metabolism*; D000872:Anthocyanins / Q000378:metabolism; D002853:Chromatography, Liquid; D005419:Flavonoids / Q000096:biosynthesis* / Q000235:genetics; D031985:Fragaria / Q000235:genetics / Q000378:metabolism*; D005638:Fruit / Q000235:genetics / Q000378:metabolism*; D013058:Mass Spectrometry; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering
D000485:Allergens; D000872:Anthocyanins; D005419:Flavonoids; D010940:Plant Proteins; D034741:RNA, Small Interfering