Investigating the role of carotenoid cleavage dioxygenase 4 in Mimulus lewisii nectar guide pigmentation
Date of Completion
Yaowu Yuan; Arlene Albert
Molecular and Cell Biology
Biodiversity | Developmental Biology | Evolution | Genetics | Molecular Biology | Molecular Genetics
Variation in the carotenoid biosynthetic pathway (CPB) in flowers is evolutionarily important due to its influence on pollinator specificity. In tomato flowers,elimination of β-carotenoid hydroxylase (BCH1) lead to an expected change in carotenoid composition, but an unexpected decrease in concentration by ~80% (Galpaz et al, 2006). Carotenoid cleavage dioxygenase 4 (CCD4) is an enzyme known to cleave carotenoids into colorless apocarotenoids. We hypothesized that CCD4 may be responsible for the observed decrease in carotenoidconcentration by selectively degrading carotenes (i.e. β-carotene) more than xanthophylls (i.e. zeaxanthin). To investigate this process in Mimulus lewisii, we developed RNAi lines for two CBP structural genes (BCH1 and ZEP1), then crossed them with a CCD4-RNAi line. Relative to the wild type, BCH1knockdown causes partial β-carotene accumulation, but a 90% decrease in total carotenoid concentration. ZEP1 knockdown causes partial zeaxanthin accumulation, but an 86% decrease in carotenoid concentration. CCD4knockdown causes a 50% increase in total carotenoid concentration, without affecting composition. Although concentration is partially restored by simultaneous knockdown of CCD4 with BCH1 or ZEP1, our data indicate thatCCD4 degrades all carotenoids non-selectively. Therefore, we suggest thatCCD4 is not responsible for the previously observed phenomenon and that differential storage capacity for carotenoids is the most likely explanation.
Struyk, Griffin, "Investigating the role of carotenoid cleavage dioxygenase 4 in Mimulus lewisii nectar guide pigmentation" (2017). Honors Scholar Theses. 603.