Journal Article

Carotenoid and ultrastructure variations in plastids of <i>Arum italicum</i> Miller fruit during maturation and ripening

Angelo Bonora, Simonetta Pancaldi, Rita Gualandri and Maria Palmira Fasulo

in Journal of Experimental Botany

Volume 51, issue 346, pages 873-884
Published in print May 2000 | ISSN: 0022-0957
Published online May 2000 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jexbot/51.346.873
Carotenoid and ultrastructure variations in plastids of Arum italicum Miller fruit during maturation and ripening

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The changes in the pigment pattern and composition occurring in the Arum italicum berry during the various steps of maturation (ivory to deep‐green stages) and ripening (yellow and red‐orange stages) were studied and correlated to the ultrastructural modifications of plastids. Transmission electron microscopy showed that each stage was characterized by a specific plastidial type following the unusual sequence amyloplast→chloroplast→chromoplast. Plastidial transitions were accompanied by profound modifications in the pigmental composition, in particular, in the pattern of carotenoids and their precursors. The HPLC analysis of the carotenoids showed that, besides the two usual all‐trans metabolic pathways leading to lutein through α‐carotene and to auroxanthin through β‐carotene, an additional cis‐isomeric biosynthetic pathway leading to cis‐neoxanthin through cis‐β‐carotene exists. During the pre‐ripening stages, the three pathways were present even if with qualitative and quantitative variations. When complete ripening was reached, a block occurred at the cyclization level causing the accumulation of both all‐trans (i.e. γ‐carotene and neurosporene) and cis‐isomer (i.e. lycopene and ζ‐carotene) carotene precursors. Because of the occurrence of unusual pigments and the presence of the three main plastidial types, the fruit of A. italicum may constitute a most instructive model for the study of carotenogenesis.

Keywords: Arum italicum Miller; carotenoid pattern; chromoplasts; fruit maturation and ripening; plastid ultrastructure.; CIMs, chromoplast internal structures; rp‐HPLC, reverse‐phase high‐performance liquid chromatography; TEM, transmission electron microscope; UV, ultraviolet light

Journal Article.  6732 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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