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
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...
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BMC
2019-11-01
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| Series: | BMC Plant Biology |
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| Online Access: | http://link.springer.com/article/10.1186/s12870-019-2078-2 |
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| author | María J. Rodrigo Joanna Lado Enriqueta Alós Berta Alquézar Orly Dery Joseph Hirschberg Lorenzo Zacarías |
| author_facet | María J. Rodrigo Joanna Lado Enriqueta Alós Berta Alquézar Orly Dery Joseph Hirschberg Lorenzo Zacarías |
| author_sort | María J. Rodrigo |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-21T12:22:44Z |
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| issn | 1471-2229 |
| language | English |
| last_indexed | 2024-12-21T12:22:44Z |
| publishDate | 2019-11-01 |
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| spelling | doaj.art-ba47db5c84474d9690d087f12918d4e72022-12-21T19:04:15ZengBMCBMC Plant Biology1471-22292019-11-0119111610.1186/s12870-019-2078-2A 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 carotenogenesisMaría J. Rodrigo0Joanna Lado1Enriqueta Alós2Berta Alquézar3Orly Dery4Joseph Hirschberg5Lorenzo Zacarías6Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC)Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC)Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC)Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC)Alexander Silberman Institute of Life Sciences, The Hebrew University of JerusalemAlexander Silberman Institute of Life Sciences, The Hebrew University of JerusalemInstituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC)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.http://link.springer.com/article/10.1186/s12870-019-2078-2Carotenoidζ-Carotene isomeraseCitrus fruit, gene expressionMutantPigmentationRipening |
| spellingShingle | María J. Rodrigo Joanna Lado Enriqueta Alós Berta Alquézar Orly Dery Joseph Hirschberg Lorenzo Zacarías 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 BMC Plant Biology Carotenoid ζ-Carotene isomerase Citrus fruit, gene expression Mutant Pigmentation Ripening |
| title | 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 |
| title_full | 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 |
| title_fullStr | 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 |
| title_full_unstemmed | 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 |
| title_short | 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 |
| title_sort | 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 |
| topic | Carotenoid ζ-Carotene isomerase Citrus fruit, gene expression Mutant Pigmentation Ripening |
| url | http://link.springer.com/article/10.1186/s12870-019-2078-2 |
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