| Abstract Detail
Monday Afternoon Morphology and Taxonomy Hirschberg, Joseph [1]. Of genes and colors: A molecular look at carotenoid biosynthesis in tomato. CAROTENOID pigments are essential components of the photosynthetic apparatus and thus are present in all green tissues of plants. These terpenoids are synthesized within the plastids from the central isoprenoid pathway through enzymes that are encoded by nuclear genes. In addition to their primary functions in photosynthesis, carotenoids play a role in plant reproduction by furnishing flowers and fruits with distinct pigmentation designed to attract animals. For this purpose they accumulate in chromoplasts. We study carotenoid biosynthesis and its regulation in flowers and fruits of tomato (S. lycopersicum), which has become a model system for chromoplast-containing plants. To this end we have cloned and analyzed genes that encode enzymes of the pathway. It was established that transcriptional regulation during fruit development is the major mechanism that controls the accumulation of lycopene in fruits. Similarly, up-regulation of genes is responsible for the accumulation of neoxanthin and violaxanthin in flowers. We have isolated novel tomato mutants with altered pigmentation of flowers or fruits. Cloning of these mutations revealed new biochemical functions that influence carotenoid accumulation. Characterization of the mutation white-flower (wf) exposed a second gene for beta-carotene hyroxylase (CrtR-b2) which is active exclusively in flowers. The existence of flower-specific CRTR-B2, geranylgeralyl diphosphate synthase (GGPS2), phytoene synthase (PSY1) and lycopene beta-cyclase (CYC-B), define a carotenoid biosynthesis pathway that is active in chromoplasts only. This finding underscores the crucial role of gene duplication in the establishment of specialized metabolic pathways in plants. We suggest that the generation of a 'chromoplast pathway' of carotenoids had appeared initially to enhance pigmentation in flowers of all wild tomato species and only later in evolution this pathway was recruited to increase fruit pigmentation in the colored-fruited species S. cheesmanii, S. pimpinellifium and S. lycopersicum.
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1 - The Hebrew University of Jerusalem, Genetics, Givat Ram, Jerusalem, 91904, Israel
Keywords:
carotenoid
regulation
biosynthesis.
Session: SOL03-2
Location: Ballroom AB/Monona Terrace
Date: Monday, July 24th, 2006
Time: 2:00 PM
Abstract ID:393 |
