The cuticular wax inhibitor locus Iw2 in wild diploid wheat Aegilops tauschii: phenotypic survey, genetic analysis, and implications for the evolution of common wheat

Nishijima, Ryo; Iehisa, Julio C. M.; Matsuoka, Yoshihiro; Takumi, Shigeo

doi:10.1186/s12870-014-0246-y

Cited by 21 publications

(27 citation statements)

References 43 publications

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“…Iw2 for non-glaucousness and B1 for awn suppression are well-known markers on 2DS and 5AL, respectively (Tsunewaki and Koba, 1979;Nishijima et al, 2014).…”

Section: Detection Of Polymorphisms and Genotyping With Markersmentioning

confidence: 99%

“…In these genotyping data were included two EST-derived sequence-tagged site markers, TE6 and WE6, that were developed with the Iw2-linked markers (Liu et al, 2007;Nishijima et al, 2014). Some single nucleotide polymorphism (SNP) markers, which were converted to cleaved amplified polymorphic sequence (CAPS) or high resolution melting (HRM) markers, were also included to enrich the number of markers.…”

Section: Detection Of Polymorphisms and Genotyping With Markersmentioning

confidence: 99%

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Quantitative trait locus analysis for flowering-related traits using two F<sub>2</sub> populations derived from crosses between Japanese common wheat cultivars and synthetic hexaploids

et al. 2015

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Flowering time is an important trait for Japanese wheat breeding. Aegilops tauschii, the D-genome donor of hexaploid wheat, is a useful resource to enlarge the D-genome diversity of common wheat. Previously, we identified floweringrelated QTLs in F 2 populations of synthetic hexaploid wheat lines between the tetraploid wheat cultivar Langdon and Ae. tauschii accessions. Here, to evaluate the usefulness of the early-flowering alleles from Ae. tauschii for Japanese wheat breeding, QTL analyses were conducted in two F 2 populations derived from crosses between Japanese wheat cultivars and early-flowering lines of synthetic hexaploid wheat. Only two chromosomal regions controlling flowering-related traits were identified, on chromosomes 2DS and 5AL in the mapping populations, and no previously identified QTLs were found in the synthetic hexaploid lines. The strong effect of the 2DS QTL, putatively corresponding to Ppd-D1, was considered to hide any significant expression of other QTLs with small effects on flowering-related traits. When F 2 individuals carrying Ae. tauschii-homozygous alleles around the 2DS QTL region were selected, the Ae. tauschii-derived alleles of the previously identified flowering QTLs partly showed an early-flowering phenotype compared with the Japanese wheat-derived alleles. Thus, some early-flowering alleles from Ae. tauschii may be useful for production of early-flowering Japanese wheat cultivars.

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“…Iw2 for non-glaucousness and B1 for awn suppression are well-known markers on 2DS and 5AL, respectively (Tsunewaki and Koba, 1979;Nishijima et al, 2014).…”

Section: Detection Of Polymorphisms and Genotyping With Markersmentioning

confidence: 99%

Section: Detection Of Polymorphisms and Genotyping With Markersmentioning

confidence: 99%

Quantitative trait locus analysis for flowering-related traits using two F<sub>2</sub> populations derived from crosses between Japanese common wheat cultivars and synthetic hexaploids

et al. 2015

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“…Further, this Iw1 fragment maps to the precise location in Ae. tauschii to which Iw2 has been fine mapped previously (12) (Fig. 6A and SI Appendix, Fig.…”

Section: Expression Of the Mirw1 Precursor In Glaucous Wheat Creates mentioning

confidence: 99%

“…In recent years, several reports have furthered the characterization of these loci, including fine-mapping of Iw1 (11), demonstrating Iw1 suppression of β-diketone wax accumulation (17), fine mapping of Iw2 in Ae. tauschii (12), comparative mapping of Iw1 and Iw2 in hexaploid wheat (18), determining the impact of W and Iw loci on glaucousness and cuticle permeability (3), and fine mapping of W1 in hexaploid wheat (19). The synthesis and chemistry of diketone waxes has been studied extensively in barley, chiefly through the characterization of loss-of-function mutants of three tightly linked loci collectively referred to as "Cer-cqu" (2,20,21).…”

Section: Significancementioning

confidence: 99%

“…Thus, because of the protective nature of the waxy β-diketone layer, the glaucous appearance has generally been selected for during the breeding of cultivated durum and bread wheat varieties (3,10). In contrast, a nonglaucous (NG) state is prevalent in the uncultivated relatives of wheat, including progenitor species wild emmer (Triticum dicoccoides, 2n = 4x = 28, AABB) and Aegilops tauschii (2n = 2x = 14, DD) (11,12). As such, these species have been used in the development of NG wheat varieties and for studies on the characterization of the genes and genetic loci involved in wax deposition, in particular W1/W2 and Iw1/Iw2 (13,14).…”

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Long noncoding miRNA gene represses wheat β-diketone waxes

Huang

Feurtado

Smith

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The cuticle of terrestrial plants functions as a protective barrier against many biotic and abiotic stresses. In wheat and other Triticeae, β-diketone waxes are major components of the epicuticular layer leading to the bluish-white glaucous trait in reproductive-age plants. Glaucousness in durum wheat is controlled by a metabolic gene cluster at the WAX1 (W1) locus and a dominant suppressor INHIBITOR of WAX1 (Iw1) on chromosome 2B. The wheat D subgenome from progenitor Aegilops tauschii contains W2 and Iw2 paralogs on chromosome 2D. Here we identify the Iw1 gene from durum wheat and demonstrate the unique regulatory mechanism by which Iw1 acts to suppress a carboxylesterase-like protein gene, W1-COE, within the W1 multigene locus. Iw1 is a long noncoding RNA (lncRNA) containing an inverted repeat (IR) with >80% identity to W1-COE. The Iw1 transcript forms a miRNA precursor-like long hairpin producing a 21-nt predominant miRNA, miRW1, and smaller numbers of related sRNAs associated with the nonglaucous phenotype. When Iw1 was introduced into glaucous bread wheat, miRW1 accumulated, W1-COE and its paralog W2-COE were down-regulated, and the phenotype was nonglaucous and β-diketone-depleted. The IR region of Iw1 has >94% identity to an IR region on chromosome 2 in Ae. tauschii that also produces miRW1 and lies within the marker-based location of Iw2. We propose the Iw loci arose from an inverted duplication of W1-COE and/or W2-COE in ancestral wheat to form evolutionarily young miRNA genes that act to repress the glaucous trait.glaucous | inhibitor of wax | small RNA | long noncoding RNA | WAX1 P lant epicuticular waxes deposited on the outer surface of the plant cuticle produce a water-resistant layer that serves to reduce nonstomatal water loss and mitigate the effects of heat and UV radiation as well as pathogen and insect attacks (1). Grasses in the Triticeae tribe, subfamily Pooideae, which include the cultivated species barley (Hordeum vulgare; 2n = 2x = 14), rye (Secale cereale, 2n = 2x = 14), durum wheat (Triticum durum; 2n = 4x = 28, AABB), and bread wheat (Triticum aestivum; 2n = 6x = 42, AABBDD), have two predominant pathways for wax production: (i) an alcohol-and alkane-rich wax pathway and (ii) a pathway leading to β-diketones and derivatives including hydroxy-β-diketones (2). The alcohol and alkane waxes are prevalent in earlier development and on leaves, whereas β-diketones dominate during the reproductive phase, particularly on leaf sheaths and flower heads (3, 4). β-Diketone wax is predominantly hentriacontane-14, 16-dione, which consists of a 31-carbon chain with carbonyl groups at C 14 and C 16 . In durum wheat, about 20% of the β-diketone is hydroxylated to form 25-hydroxy-β-diketone, whereas in bread wheat hydroxylation is at C 8 or C 9 (5). β-Diketone wax deposition manifests visibly as glaucousness, a bluish-white coloration on stems, leaves, and flower heads. However, the relationship between a glaucous appearance and the total amount of cuticular wax can be inconsistent, especially during t...

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