Leaf sheath cuticular waxes on bloomless and sparse-bloom mutants of Sorghum bicolor

Jenks, Matthew A.; Rich, Patrick J.; Rhodes, David; Ashworth, Edward N.; Axtell, John D.; Ding, Chang

doi:10.1016/s0031-9422(00)00153-9

Cited by 46 publications

(34 citation statements)

References 21 publications

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“…FLs add another layer of protection to the plant, against UV radiation and possibly against pathogen attack. Our observations are consistent with earlier reports (21) from various studies of monocots; e.g., on accumulation of CW on emerging leak leaves, secretion of CW by cork cells of the leaf abaxial epidermis in sorghum, greatly affected in bloomless mutants (22,23), and on rapid accumulation of FLs in young leaves of barley as they emerge from the coleoptile (24).…”

Section: Discussionsupporting

confidence: 93%

Complex nested promoters control tissue-specific expression of acetyl-CoA carboxylase genes in wheat

Zuther¹,

Huang²,

Jeleńska³

et al. 2004

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

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Cis-acting regulatory elements of the wheat acetyl-CoA carboxylase (ACC) gene family were identified by comparing the promoter activity of 5 end gene fragments fused to a reporter gene in two transient expression systems: wheat protoplasts and epidermal cells of mature embryos. Expression of the plastid and the cytosolic ACC genes is each driven by two nested promoters responsible for the synthesis of two transcript types. The internal promoter is located in an intron removed from transcripts originating at the first promoter. These complex promoters, which are different for the cytosolic and plastid ACC genes, control tissue-specific expression of the enzymatic activity supplying cytosolic, plastid, and mitochondrial pools of malonyl-CoA. The activity of one such complex promoter, driving expression of one of the cytosolic ACC genes, was studied throughout development of transgenic wheat plants carrying a full-length promoter-reporter gene fusion. High activity of the promoter was detected in the coleoptile, in the upper sheath section of the leaf, on the top surface of the ovary, in some sections of the main veins in the lemma and glume, and in abaxial epidermis hair cells of the lemma, glume, and rachis. The findings are consistent with the developmental and environmental requirements for very-long-chain fatty acids and flavonoids, whose synthesis begins with the ACC reaction in the cytosol of these specific cell types.M odern bread wheat has a large hexaploid genome, making molecular genetic studies difficult. We have been studying the structure, evolution, and function of the family of genes encoding the enzyme acetyl-CoA carboxylase (ACC) during wheat development (1-7).In plants, separate ACC isozymes supply the malonyl-CoA pools used for de novo fatty acid (FA) biosynthesis in plastids and mitochondria, and for FA elongation and flavonoid (FL) and stilbene biosynthesis in the cytosol (8, 9). FAs are essential in membrane biogenesis, lipoic acid synthesis, production of oil as storage material, cuticular wax (CW) synthesis, signaling, and pollen-stigma interaction. FLs play multiple roles in plants as pigments and UV protectants, defense compounds, and as signals (10). Malonyl-CoA is also used for protein and smallmolecule malonylation.Our previous study (5) showed that significant regulation of cytosolic and plastid ACC genes in young wheat plants is accomplished at the transcript level. The number and identity of transcribed genes were established by cDNA and genomic DNA sequence comparisons. Transcription start sites and splicing patterns of leader introns were identified for multiple genes, including homoeologs and paralogs. We found that in wheat seedlings, the plastid ACC mRNA level is high in the middle part of the plant and low in roots and leaf blades. The three plastid ACC-homoeologous genes are equivalent in their level of expression. Cytosolic ACC mRNA accumulates to a high level in the lower sheath section of the plant. For the cytosolic ACC genes, we found that transcripts of the three homoeo...

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Section: Discussionsupporting

confidence: 93%

Complex nested promoters control tissue-specific expression of acetyl-CoA carboxylase genes in wheat

Zuther¹,

Huang²,

Jeleńska³

et al. 2004

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

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“…The reason for the increase in wax amount on rst1 null mutant leaves is unknown. This condition is not without precedent, however, as cuticle mutants in Sorghum, such as bm4, that have reduced leaf sheath waxes have increased leaf blade waxes (Rich, 1994;Jenks et al, 2000). Further studies are needed to investigate whether RST1 may act as a negative regulator of the wax pathway in Arabidopsis leaves.…”

Section: Discussionmentioning

confidence: 99%

Mutation of the RESURRECTION1 Locus of Arabidopsis Reveals an Association of Cuticular Wax with Embryo Development

et al. 2005

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(S.M.G., X.L., Xinlu C., R.A.B., M.A.J.)Insertional mutagenesis of Arabidopsis (Arabidopsis thaliana) was used to identify a novel recessive mutant, designated resurrection1 (rst1), which possesses a dramatic alteration in its cuticular waxes and produces shrunken nonviable seeds due to arrested embryo development. The RST1 gene sequence associated with these phenotypes was verified by three independent, allelic, insertion mutants, designated rst1-1, rst1-2, and rst1-3, with inserts in the first exon, 12th intron, and fourth exon, respectively. These three rst1 allelic mutants have nearly identical alterations in their wax profiles and embryo development. Compared to wild type, the wax on rst1 inflorescence stems is reduced nearly 60% in total amount, has a proportional reduction in aldehydes and aldehyde metabolites, and has a proportional increase in acids, primary alcohols, and esters. Compared to wild type, the C 29 alkanes on rst1 are nearly 6-fold lower, and the C 30 primary alcohols are 4-fold higher. These results indicate that rst1 causes shunting of most wax precursors away from alkane synthesis and into the primary-alcoholproducing branch of the pathway. In contrast to stems, the wax on rst1 mutant leaves increased roughly 43% in amount relative to the wild type, with the major increase occurring in the C 31 and C 33 alkanes. Unique among known wax mutants, approximately 70% of rst1 seeds are shrunken and nonviable, with these being randomly distributed within both inflorescence and silique. Viable seeds of rst1 are slightly larger than those of wild type, and although the viable rst1 seeds contain more total triacylglycerol-derived fatty acids, the proportions of these fatty acids are not significantly different from wild type. Shrunken seeds contain 34% of the fatty acids of wild-type seeds, with proportionally more palmitic, stearic, and oleic acids, and less of the longer and more desaturated homologs. Histological analysis of aborted rst1 seeds revealed that embryo development terminates at the approximate heart-shaped stage, whereas viable rst1 and wild-type embryos develop similarly. The RST1 gene encodes a predicted 1,841-amino acid novel protein with a molecular mass of 203.6 kD and a theoretical pI of 6.21. The RST1 transcript was found in all tissues examined including leaves, flowers, roots, stems, and siliques, but accumulation levels were not correlated with the degree to which different organs appeared affected by the mutation. The new RST1 gene reveals a novel genetic connection between lipid synthesis and embryo development; however, RST1's exact role is still quite unknown. The degree to which RST1 is associated with lipid signaling in development is an important focus of ongoing studies.Plant lipids, including phospholipids (Meijer and Munnik, 2003), sterols (He et al., 2003), sphingolipids (Sperling and Heinz, 2003), fatty acids, and their derivatives like jasmonate (Turner et al., 2002;Weber, 2002), can serve as important signal molecules in the regulation of plant development. Re...

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“…The bm2 mutant has Ͼ 60% reduction in cuticle membrane weight and thickness (Jenks et al, 1994) and a significant alteration in its waxes (Jenks et al, 2000). The BM2 gene has not been cloned.…”

Section: Introductionmentioning

confidence: 99%

Cloning and Characterization of the WAX2 Gene of Arabidopsis Involved in Cuticle Membrane and Wax Production

et al. 2003

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Insertional mutagenesis of Arabidopsis ecotype C24 was used to identify a novel mutant, designated wax2 , that had alterations in both cuticle membrane and cuticular waxes. Arabidopsis mutants with altered cuticle membrane have not been reported previously. Compared with the wild type, the cuticle membrane of wax2 stems weighed 20.2% less, and when viewed using electron microscopy, it was 36.4% thicker, less opaque, and structurally disorganized. The total wax amount on wax2 leaves and stems was reduced by Ͼ 78% and showed proportional deficiencies in the aldehydes, alkanes, secondary alcohols, and ketones, with increased acids, primary alcohols, and esters. Besides altered cuticle membranes, wax2 displayed postgenital fusion between aerial organs (especially in flower buds), reduced fertility under low humidity, increased epidermal permeability, and a reduction in stomatal index on adaxial and abaxial leaf surfaces. Thus, wax2 reveals a potential role for the cuticle as a suppressor of postgenital fusion and epidermal diffusion and as a mediator of both fertility and the development of epidermal architecture (via effects on stomatal index). The cloned WAX2 gene (verified by three independent allelic insertion mutants with identical phenotypes) codes for a predicted 632-amino acid integral membrane protein with a molecular mass of 72.3 kD and a theoretical pI of 8.78. WAX2 has six transmembrane domains, a His-rich diiron binding region at the N-terminal region, and a large soluble C-terminal domain. The N-terminal portion of WAX2 is homologous with members of the sterol desaturase family, whereas the C terminus of WAX2 is most similar to members of the short-chain dehydrogenase/reductase family. WAX2 has 32% identity to CER1, a protein required for wax production but not for cuticle membrane production. Based on these analyses, we predict that WAX2 has a metabolic function associated with both cuticle membrane and wax synthesis. These studies provide new insight into the genetics and biochemistry of plant cuticle production and elucidate new associations between the cuticle and diverse aspects of plant development.

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Leaf sheath cuticular waxes on bloomless and sparse-bloom mutants of Sorghum bicolor

Cited by 46 publications

References 21 publications

Complex nested promoters control tissue-specific expression of acetyl-CoA carboxylase genes in wheat

Complex nested promoters control tissue-specific expression of acetyl-CoA carboxylase genes in wheat

Mutation of the RESURRECTION1 Locus of Arabidopsis Reveals an Association of Cuticular Wax with Embryo Development

Cloning and Characterization of the WAX2 Gene of Arabidopsis Involved in Cuticle Membrane and Wax Production

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