title: Genetic background impacts soluble and cell wall-bound aromatics in brown midrib mutants of sorghum.
abstract: Sorghum (Sorghum bicolor (L.). Moench) BMR-6 and BMR-12 encode cinnamylalcohol dehydrogenase and caffeic acid-O-methyltransferase, respectively. We have evaluated the impact of two bmr alleles, bmr-6 and bmr-12, respectively, on soluble and wall-bound aromatics in near isogenic, wild-type (WT), bmr-6, bmr-12 and double-mutant (DM; bmr-6 and bmr-12) plants in two genetic backgrounds, RTx430 and Wheatland. Immunoblots confirmed that COMT protein was essentially absent in bmr-12 and DM plants, but was present in bmr-6 and WT plants. In contrast, although CAD activity was not detected in bmr-6 and DM plants, proteins crossreacting to anti-CAD sera were found in stem extracts from all genotypes. In both sorghum backgrounds, WT plants had lowest amounts of free aromatics, higher levels of cell wall-bound pCA and FA esters and guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H) lignins. Soluble aromatics and cell wall phenolic ester content in Wheatland DM plants resembled that of Wheatland bmr-6 plants, whereas in the RTx430 background, levels of these components in the DM plants more closely resembled those observed in bmr-12 plants. In both backgrounds, bmr-6 plants exhibited reduced levels of G, S, and H lignins relative to WT, and increased incorporation of G-indene into lignin. In bmr-12 plants, there was greater incorporation of G- and 5-hydroxyguaiacyl (5-OHG) lignin into cell walls. Histochemical staining of internode sections from Wheatland plants indicated that apparent lignification of cortical sclerenchyma and vascular bundle fibers was greatest and most uniform in WT plants. Relative staining intensity of these tissues was decreased in bmr-6, followed by bmr-12 plants. DM plants exhibited poor staining of cortical sclerenchyma and vascular bundle fibers.
authors.affiliation: Grain, Forage and Bioenergy Research Unit, USDA-ARS, University of Nebraska-Lincoln, East Campus, 314 Biochemistry Hall, Lincoln, NE 68583-0737, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Palmer
authors.forename: Scott E
authors.initials: SE
authors.lastname: Sattler
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Saathoff
authors.forename: Deanna
authors.initials: D
authors.lastname: Funnell
authors.forename: Jeffery F
authors.initials: JF
authors.lastname: Pedersen
authors.forename: Gautam
authors.initials: G
authors.lastname: Sarath
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D003373:Coumaric Acids / Q000378:metabolism; D004951:Esterification; D008401:Gas Chromatography-Mass Spectrometry; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D015151:Immunoblotting; D008031:Lignin / Q000096:biosynthesis; D009154:Mutation / Q000235:genetics*; D010088:Oxidoreductases / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018547:Plant Stems / Q000166:cytology / Q000378:metabolism; D012995:Solubility; D045868:Sorghum / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D014020:Tissue Extracts
chemical_list: D003373:Coumaric Acids; D006841:Hydrocarbons, Aromatic; D010940:Plant Proteins; D014020:Tissue Extracts; D008031:Lignin; C004999:ferulic acid; D010088:Oxidoreductases
references.citation: Annu Rev Plant Biol. 2003;54:519-46
references.pmid: 14503002
references.citation: J Agric Food Chem. 2002 Jun 19;50(13):3789-94
references.pmid: 12059161
references.citation: J Biol Chem. 2000 Mar 3;275(9):6537-45
references.pmid: 10692459
references.citation: Planta. 1991 Nov;185(4):538-44
references.pmid: 24186532
references.citation: Nat Biotechnol. 2007 Jul;25(7):759-61
references.pmid: 17572667
references.citation: Proc Natl Acad Sci U S A. 1999 Aug 31;96(18):10045-50
references.pmid: 10468559
references.citation: Theor Appl Genet. 2002 Jan;104(1):127-31
references.pmid: 12579437
references.citation: J Ind Microbiol Biotechnol. 2008 May;35(5):343-354
references.pmid: 18205019
references.citation: Nature. 1970 Aug 15;227(5259):680-5
references.pmid: 5432063
references.citation: BMC Genomics. 2007 Jan 18;8:22
references.pmid: 17233901
references.citation: Plant J. 1998 Jun;14(5):545-53
references.pmid: 9675900
references.citation: Phytochemistry. 2002 Oct;61(3):221-94
references.pmid: 12359514
references.citation: Plant Physiol. 1993 Jun;102(2):481-489
references.pmid: 12231836
references.citation: Phytochemistry. 2001 Aug;57(7):1069-84
references.pmid: 11430980
references.citation: Bioresour Technol. 2007 Nov;98(16):2985-92
references.pmid: 17156999
references.citation: Proc Natl Acad Sci U S A. 2008 Jan 15;105(2):464-9
references.pmid: 18180449
references.citation: Plant Physiol Biochem. 2008 Mar;46(3):356-70
references.pmid: 18272377
references.citation: Planta. 2007 Jun;226(1):235-50
references.pmid: 17226026
references.citation: Mol Genet Genomics. 2003 May;269(2):205-14
references.pmid: 12756532
references.citation: J Biol Chem. 2002 Dec 6;277(49):47412-9
references.pmid: 12351655
references.citation: Planta. 2005 Mar;220(5):678-88
references.pmid: 15452707
references.citation: C R Biol. 2004 Sep-Oct;327(9-10):847-60
references.pmid: 15587076
references.citation: Phytochemistry. 2007 Jun;68(11):1521-9
references.pmid: 17466347
references.citation: Plant Mol Biol. 2006 Nov;62(4-5):697-714
references.pmid: 17016741
references.citation: Phytochemistry. 2007 Jul;68(14):1957-74
references.pmid: 17467016
references.citation: Planta. 2004 Nov;220(1):56-63
references.pmid: 15252733
references.citation: Planta. 2007 Aug;226(3):741-51
references.pmid: 17457604
references.citation: J Agric Food Chem. 2002 Sep 25;50(20):5558-65
references.pmid: 12236679