Esterified carotenoids are synthesized in petals of carnation (Dianthus caryophyllus) and accumulate in differentiated chromoplasts

Abstract

Although yellow and orange petal colors are derived from carotenoids in many plant species, this has not yet been demonstrated for the order Caryophyllales, which includes carnations. Here, we identified a carnation cultivar with pale yellow flowers that accumulated carotenoids in petals. Additionally, some xanthophyll compounds were esterified, as is the case for yellow flowers in other plant species. Ultrastructural analysis showed that chromoplasts with numerous plastoglobules, in which flower-specific carotenoids accumulate, were present in the pale yellow petals. RNA-seq and RT-qPCR analyses indicated that the expression levels of genes for carotenoid biosynthesis and esterification in pale yellow and pink petals (that accumulate small amounts of carotenoids) were similar or lower than in green petals (that accumulate substantial amounts of carotenoids) and white petals (that accumulate extremely low levels of carotenoids). Pale yellow and pink petals had a considerably lower level of expression of genes for carotenoid degradation than white petals, suggesting that reduced degradation activity caused accumulation of carotenoids. Our results indicate that some carnation cultivars can synthesize and accumulate esterified carotenoids. By manipulating the rate of biosynthesis and esterification of carotenoids in these cultivars, it should be feasible to produce novel carnation cultivars with vivid yellow flowers.

The Carotenoid Esterification Gene BrPYP Controls Pale-Yellow Petal Color in Flowering Chinese Cabbage (Brassica rapa L. subsp. parachinensis)

“…The PGs in chromoplasts are much bigger than those in chloroplasts and contain more xanthophyll esters, which are formed during the degradation of carotenoids ( Mulisch and Krupinska, 2013 ). However, irregularly shaped PGs, and disorganized and electron-lucent membrane structures lead to a decrease in carotenoid, as found in carnations, tomato, and B. juncea ( Ariizumi et al, 2014 ; Zhang X. et al, 2018 ; Iijima et al, 2020 ). In this study, far fewer well-developed PGs were observed in the pale-yellow petals of flowering Chinese cabbage, suggesting that insufficient PGs reduces accumulation of carotenoid esters.…”

Xanthophyll esterases in association with fibrillins control the stable storage of carotenoids in yellow flowers of rapeseed (Brassica juncea)

“…Xanthophyll esterification is catalyzed by xanthophyll esterases (XES) or xanthophyll acyltransferase (XAT), which promote the transfer of broad fatty acid acyl donors to acceptors with the hydroxyl group of xanthophylls (Watkins et al ., 2019). Several XESs including PYP1 , IoXES , TeXES , XES1 , XES2 , and BrWF3 / BrPYP share homology with the Arabidopsis esterase/lipase/thioesterase (ELT) gene family, while being associated with xanthophyll esterification in flowers of tomato, Ipomoea obscura , marigold, carnation, and Chinese cabbage (Ariizumi et al ., 2014; Iijima et al ., 2020; Kishimoto et al ., 2020; Yang et al ., 2021; Li et al ., 2022). In addition, an XAT gene belonging to the Gly‐Asp‐Ser‐Leu (GDSL) esterase/lipase gene family has been verified to affect lutein esterification in bread wheat grain (Watkins et al ., 2019).…”

Transcriptome Analysis of Key Genes Involved in Color Variation between Blue and White Flowers of Iris bulleyana

“…Flavonoids/anthocyanins and carotenoids are often present in the same organs, and their combination increases color variety. The synthesis pathways of these two types of pigments are well characterized [23,26,27,[32][33][34][35] and have been attributed to many plant species, i.e., Arabidopsis thaliana [36], Rosa rugosa [23], Dianthus caryophyllus [37], and Dracocephalum moldavica [38]. Betalains, water-soluble metabolites, yellow-to-red nitrogencontaining compounds are derived from tyrosine.…”