Overexpression of carotenogenic genes in the Japanese morning glory <i>Ipomoea</i> (<i>Pharbitis</i>) <i>nil</i>

Abstract

Japanese morning glory, Ipomoea nil, has several coloured flowers except yellow, because it can accumulate only trace amounts of carotenoids in the petal. To make the petal yellow with carotenoids, we introduced five carotenogenic genes (geranylgeranyl pyrophosphate synthase, phytoene synthase, lycopene β-cyclase and β-ring hydroxylase from Ipomoea obscura var. lutea and bacterial phytoene desaturase from Pantoea ananatis) to white-flowered I. nil cv. AK77 with a petal-specific promoter by Rhizobium (Agrobacterium)-mediated transformation method. We succeeded to produce transgenic plants overexpressing carotenogenic genes. In the petal of the transgenic plants, mRNA levels of the carotenogenic genes were 10 to 1,000 times higher than those of non-transgenic control. The petal colour did not change visually; however, carotenoid concentration in the petal was increased up to about ten-fold relative to non-transgenic control. Moreover, the components of carotenoids in the petal were diversified, in particular, several β-carotene derivatives, such as zeaxanthin and neoxanthin, were newly synthesized. This is the first report, to our knowledge, of changing the component and increasing the amount of carotenoid in petals that lack ability to biosynthesize carotenoids.

Alteration of Flower Color in Viola cornuta cv. “Lutea Splendens” through Metabolic Engineering of Capsanthin/Capsorubin Synthesis

“…SD-212 [31] or green algae, Hematococcus pluvialis [68]. In most cases flower color alterations in whole flower or some flower parts in derived transgenic plants were observed, although in some cases no visible change in flower color occurred, despite the expression of the transgene [67,69]. In this work, we demonstrate the introduction of the capsanthin-capsorubin synthase gene from the ornamental plant, Lilium lancifolium, and its expression in another ornamental plant, V. cornuta.…”

Molecular Basis of Carotenoid Accumulation in Horticultural Crops

“…The steady-state level of carotenoids is partly dependent on the metabolic equilibrium between the biosynthesis and degradation of carotenoids. However, simply manipulating the carotenoid metabolic pathway does not always result in a drastic change in carotenoid accumulation (Watanabe et al, 2017(Watanabe et al, , 2018. One possible explanation for this phenomenon is that there may be a factor affecting carotenoid accumulation besides carotenoid metabolism.…”

Construction of transgenic <i>Ipomoea obscura</i> that exhibits new reddish leaf and flower colors due to introduction of β-carotene ketolase and hydroxylase genes

“…Modern techniques in plant biotechnology, such as somatic hybrid formation and plant-host transformation followed by its regeneration, are expected to enable further breeding of ornamental Ipomoea species. As for Japanese morning glory (I. nil), many reports have been published on its tissue culture (Jia and Chua 1992;Shimizu et al 2003Shimizu et al , 2005Yoneda and Nakamura 1987), on its transformation (Kikuchi et al 2005;Ono et al 2000;Shibuya et al 2014;Takatori et al 2015;Watanabe et al 2017b) and on its genome editing (Watanabe et al 2017a(Watanabe et al , 2018, whereas few reports have described embryogenic callus formation and plant regeneration in other ornamental Ipomoea species (Ishikuro et al 2014).…”