Analysis of cuticular wax constituents and genes that contribute to the formation of ‘glossy Newhall’, a spontaneous bud mutant from the wild-type ‘Newhall’ navel orange

Abstract

Navel orange (Citrus sinensis [L.] Osbeck) fruit surfaces contain substantial quantities of cuticular waxes, which have important eco-physiological roles, such as water retention and pathogen defense. The wax constituents of ripe navel orange have been studied in various reports, while the wax changes occurring during fruit development and the molecular mechanism underlying their biosynthesis/export have not been investigated. Recently, we reported a spontaneous bud mutant from the wild-type (WT) 'Newhall' Navel orange. This mutant displayed unusual glossy fruit peels and was named 'glossy Newhall' (MT). In this study, we compared the developmental profiles of the epicuticular and intracuticular waxes on the WT and MT fruit surfaces. The formation of epicuticular wax crystals on the navel orange surface was shown to be dependent on the accumulation of high amounts of aliphatic wax components with trace amounts of terpenoids. In sharp contrast, the underlying intracuticular wax layers have relatively low concentrations of aliphatic wax components but high concentrations of cyclic wax compounds, especially terpenoids at the late fruit developmental stages. Our work also showed that many genes that are involved in wax biosynthesis and export pathways were down-regulated in MT fruit peels, leading to a decrease in aliphatic wax component amounts and the loss of epicuticular wax crystals, ultimately causing the glossy phenotype of MT fruits.

Changes in Cuticle Components and Morphology of ‘Satsuma’ Mandarin (Citrus unshiu) during Ambient Storage and Their Potential Role on Penicillium digitatum Infection

“…Previous reports have studied the infectious processes and mechanism of Penicillium digitatum for citrus fruits [27][28][29]. Despite the diversity of citrus cuticle composition and architecture being reported [5][6][7][8]10], information about the variations in the chemical composition of citrus fruit cuticle during storage, especially their potential roles in Penicillium digitatum infection, is not available. Similarly, there is a limited understanding of the relative importance and differing roles of waxes and cutin.…”

Analysis of biosynthesis and composition of cuticular wax in wild type bilberry (Vaccinium myrtillusL.) and its glossy mutant

“…It has been previously reported that mutations in wax biosynthesis causing glossy surface in Arabidopsis leaf and stem show reduced density of wax crystals and sometimes also alterations in the crystal shape and size (Jenks et al ., 1996). Similar results has been obtained in studies on surfaces of glossy fruits of orange (Liu et al ., 2012; 2015) and cucumber (Wang et al ., 2015a,b). Our study also demonstrated a decrease in the density of epicuticular wax crystal structures in GT fruit compared to WT fruit.…”

“…Characterization of naturally occurring glaucous lines have identified β-diketones to be responsible for glaucousness in wheat and barley (Hen-Avivi et al ., 2016). Among fruits, orange glossy type mutant fruits showed a decrease in wax load accompanied by reduction in proportion of aldehydes affecting crystalloid formation (Liu et al ., 2012; 2015). In cucumber, CsCER1 -RNAi transgenic lines showing glossy phenotype demonstrated inhibited wax crystallization attributed to decrease in proportion of alkanes as compared to wild type lines (Wang et al ., 2015b).…”

“…There are only few studies of wax biosynthesis in fruits and the studies have mostly focused on horticultural plants, such as tomato ( Solanum lycopersicum L., Mintz-Oron et al ., 2008), sweet cherry ( Prunus avium L., Alkio et al ., 2012), apple ( Malus domestica L., Albert et al ., 2013), orange ( Citrus sinensis L., Liu et al ., 2015; Wang et al ., 2016), mango ( Mangifera indica L., Tafolla-Arellano et al ., 2017), and cucumber ( Cucumis sativus L., Wang et al ., 2015a,b; Wang et al ., 2018). Bilberries ( Vaccinium myrtillus L.) are deciduous shrubs with wide distribution in cool temperate regions and mountain areas of Europe and Asia.…”

The Acyl Desaturase CER17 Is Involved in Producing Wax Unsaturated Primary Alcohols and Cutin Monomers

“…Similarly, monounsaturates have been reported as trace components in the waxes of naval orange (Citrus sinensis) fruit (Liu et al, 2015). Alkenes have been reported in the waxes of rice and maize silks (Perera et al, 2010;Qin et al, 2013).…”