A mutant allele of ζ-carotene isomerase (Z-ISO) is associated with the yellow pigmentation of the "pinalate" sweet orange mutant and reveals new insights into its role in fruit carotenogenesis.
- Autor(es):
- RODRIGO, M.J. ; LADO, J. ; ALÓS, E. ; ALQUÉZAR, B. ; DERY, O. ; HIRSCHBERG, J. ; ZACARÍAS, L.
- Tipo:
- Artículo
- Versión:
- Publicado
- Resumen:
-
Abstract.Background: Fruit coloration is one of the main quality parameters of Citrus fruit primarily determined by genetic factors. The fruit of ordinary sweet orange (Citrus sinensis) displays a pleasant orange tint due to accumulation of carotenoids, representing β,β-xanthophylls more than 80% of the total content. 'Pinalate' is a spontaneous bud mutant, or somatic mutation, derived from sweet orange 'Navelate', characterized by yellow fruits due to elevated proportions of upstream carotenes and reduced β,β-xanthophylls, which suggests a biosynthetic blockage at early steps of the carotenoid pathway. Results: To identify the molecular basis of 'Pinalate' yellow fruit, a complete characterization of carotenoids profile together with transcriptional changes in carotenoid biosynthetic genes were performed in mutant and parental fruits during development and ripening. 'Pinalate' fruit showed a distinctive carotenoid profile at all ripening stages, accumulating phytoene, phytofluene and unusual proportions of 9,15,9′-tri-cis- and 9,9′-di-cis-ζ-carotene, while content of downstream carotenoids was significantly decreased. Transcript levels for most of the carotenoid biosynthetic genes showed no alterations in 'Pinalate'; however, the steady-state level mRNA of ζ-carotene isomerase (Z-ISO), which catalyses the conversion of 9,15,9′-tri-cis- to 9,9′-di-cis-ζ-carotene, was significantly reduced both in 'Pinalate' fruit and leaf tissues. Isolation of the 'Pinalate' Z-ISO genomic sequence identified a new allele with a single nucleotide insertion at the second exon, which generates an alternative splicing site that alters Z-ISO transcripts encoding non-functional enzyme. Moreover, functional assays of citrus Z-ISO in E.coli showed that light is able to enhance a non-enzymatic isomerization of tri-cis to di-cis-ζ-carotene, which is in agreement with the partial rescue of mutant phenotype when 'Pinalate' fruits are highly exposed to light during ripening. Conclusion: A single nucleotide insertion has been identified in 'Pinalate' Z-ISO gene that results in truncated proteins. This causes a bottleneck in the carotenoid pathway with an unbalanced content of carotenes upstream to β,β-xanthophylls in fruit tissues. In chloroplastic tissues, the effects of Z-ISO alteration are mainly manifested as a reduction in total carotenoid content. Taken together, our results indicate that the spontaneous single nucleotide insertion in Z-ISO is the molecular basis of the yellow pigmentation in 'Pinalate' sweet orange and points this isomerase as an essential activity for carotenogenesis in citrus fruits. © 2019 The Author(s).
- Año:
- 2019
- Idioma:
- Inglés
- Temas:
- Carotenoid
Zeta-carotene isomerase
GENE EXPRESSION
MUTANT
Pigmentation
RIPENING
PLATAFORMA AGROALIMENTOS
CAROTENOIDES
CITRUS
- Institución:
- Instituto Nacional de Investigación Agropecuaria
- Repositorio:
- Ainfo
- Enlace(s):
- http://www.ainfo.inia.uy/consulta/busca?b=pc&id=60661&biblioteca=vazio&busca=60661&qFacets=60661
- Nivel de acceso:
- Acceso abierto