Metabolic and gene expression analysis of apple (Malus x domestica) carotenogenesis.
Carotenoid accumulation confers distinct colouration to plant tissues, with effects on plant response to light and as well as health benefits for consumers of plant products. The carotenoid pathway is controlled by flux of metabolites, rate-limiting enzyme steps, feed-back inhibition, and the strength of sink organelles, the plastids, in the cell. In apple (Malus × domestica Borkh), fruit carotenoid concentrations are low in comparison with those in other fruit species. The apple fruit flesh, in particular, begins development with high amounts of chlorophylls and carotenoids, but in all commercial cultivars a large proportion of this is lost by fruit maturity. To understand the control of carotenoid concentrations in apple fruit, metabolic and gene expression analysis of the carotenoid pathway were measured in genotypes with varying flesh and skin colour. Considerable variation in both carotenoid concentrations and compound profile was observed between tissues and genotypes, with carotenes and xanthophylls being found only in fruit accumulating high carotenoid concentrations. The study identified potential rate-limiting steps in carotenogenesis, which suggested that the expression of ZISO, CRTISO, and LCY-ε, in particular, were significant in predicting final carotenoid accumulation in mature apple fruit.
The New Zealand Institute for Plant & Food Research Limited (PFR), Private Bag 92 169,  Auckland, New Zealand.
Charles
C
Ampomah-Dwamena
Supinya
S
Dejnoprat
David
D
Lewis
Paul
P
Sutherland
Richard K
RK
Volz
Andrew C
AC
Allan
D002338:Carotenoids / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D020224:Expressed Sequence Tags; D005638:Fruit / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D005838:Genotype; D027845:Malus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism / Q000648:ultrastructure; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013045:Species Specificity
D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D002734:Chlorophyll; D002338:Carotenoids