W3 Is a New Wax Locus That Is Essential for Biosynthesis of β-Diketone, Development of Glaucousness, and Reduction of Cuticle Permeability in Common Wheat

Abstract

The cuticle plays important roles in plant development, growth and defense against biotic and abiotic attacks. Crystallized epicuticular wax, the outermost layer of cuticle, is visible as white-bluish glaucousness. In crops like barley and wheat, glaucousness is trait of adaption to the dry and hot cultivation conditions, and hentriacontane-14,16-dione (β-diketone) and its hydroxy derivatives are the major and unique components of cuticular wax in the upper parts of adult plants. But their biosynthetic pathway and physiological role largely remain unknown. In the present research, we identified a novel wax mutant in wheat cultivar Bobwhite. The mutation is not allelic to the known wax production gene loci W1 and W2, and designated as W3 accordingly. Genetic analysis localized W3 on chromosome arm 2BS. The w3 mutation reduced 99% of β-diketones, which account for 63.3% of the total wax load of the wild-type. W3 is necessary for β-diketone synthesis, but has a different effect on β-diketone hydroxylation because the hydroxy-β-diketones to β-diketone ratio increased 11-fold in the w3 mutant. Loss of β-diketones caused failure to form glaucousness and significant increase of cuticle permeability in terms of water loss and chlorophyll efflux in the w3 mutant. Transcription of 23 cuticle genes from five functional groups was altered in the w3 mutant, 19 down-regulated and four up-regulated, suggesting a possibility that W3 encodes a transcription regulator coordinating expression of cuticle genes. Biosynthesis of β-diketones in wheat and their implications in glaucousness formation and drought and heat tolerance were discussed.Key Message W3 is essential for β-diketone biosynthesis but suppresses its hydroxylation. Loss-of-function mutation w3 significantly increased cuticle permeability in terms of water loss and chlorophyll efflux.

TaCER1‐1A is involved in cuticular wax alkane biosynthesis in hexaploid wheat and responds to plant abiotic stresses

“…The wheat waxes comprise various classes of VLC aliphatics including β‐diketones, alkanes, and primary alcohols, similar to many other monocots and dicots. Recent reports revealed that β‐diketone formation largely depends on genes clustered in the W1, W2, and W3 loci residing on different chromosomes in separate subgenomes (Adamski et al, ; Tsunewaki & Ebana, ; Zhang et al, ). Other studies showed that at least eight functional FAR enzymes are involved in formation of VLC primary alcohols, all with different expression profiles (Chai et al, ; Wang, et al, 2015b; Wang, et al, 2015c; Wang et al, ).…”

Cuticular Wax Accumulation Is Associated with Drought Tolerance in Wheat Near-Isogenic Lines

“…Previous studies have indicated that leaf cuticular wax is associated with plant drought tolerance in many species, such as Arabidopsis , cotton and wheat (Bondada et al, 1996; Kosma et al, 2009; Zhang et al, 2015). And Chatterton et al (1975) reported that sorghum yield was associated with cuticular wax; however, wheat drought tolerance conferred by cuticular wax has rarely been studied with NILs in wheat (Uddin and Marshall, 1988; Araus et al, 1991; Zhang et al, 2005; Cameron et al, 2006; Kim et al, 2007; Yang et al, 2011).…”

“…To date, six genes controlling wax biosynthesis have been reported and are located on the following wheat chromosomes: W1 and IW1 on 2BS, W2 and IW2 on 2DS, W3 on 2BS, and IW3 on 1BS (Tsunewaki and Ebana, 1999; Adamski et al, 2013; Wu et al, 2013; Wang et al, 2014a; Zhang et al, 2015), but little is known about the functions of these genes. Previous studies showed that leaf cuticular wax can protect the plants against abiotic and biotic stresses, such as drought, UV and the wheat grain aphid (Blum and Ebercon, 1981; Shepherd and Wynne Griffiths, 2006; Wójcicka, 2015).…”

A Metabolic Gene Cluster in the Wheat W1 and the Barley Cer-cqu Loci Determines β-Diketone Biosynthesis and Glaucousness

“…Importantly, both CYP96B30 and WES were found to be highly coexpressed with the three cluster genes DMP, DMH, and DMC. Recently, Zhang et al (2015) identified the W3 locus, which is linked to W1, and suggested its involvement in b-diketone biosynthesis. Given the complexity of the W1/Iw1 region, W3 might be included in this interval.…”

“…In particular, many Poaceae species (including wheat [Triticum spp], barley [Hordeum vulgare], rye [Secale cereale], and oat [Avena sativa]) produce very-long-chain b-diketones with characteristic structures likely formed along pathways different from those leading to more ubiquitous wax compounds (Supplemental Figure 1). Despite many years of research on b-diketone biosynthesis, particularly in barley and wheat (von Wettstein-Knowles, 1976, 1995von Wettstein-Knowles and Søgaard, 1980;Adamski et al, 2013;Zhang et al, 2013Zhang et al, , 2015, the genes and enzymes involved remain to be discovered.…”