Alterations of the degree of xylan acetylation in<i>Arabidopsis</i>xylan mutants

Lee, Chanhui; Teng, Quincy; Zhong, Ruiqin; Ye, Zheng‐Hua

doi:10.4161/psb.27797

Cited by 17 publications

(19 citation statements)

References 23 publications

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“…This possibility was in agreement with the observation that the esk1 mutation resulted in an increase in the MeGlcA level [ 39 ]. In contrast, the gux1/2/3 xylan, which lacked GlcA substitutions [ 40 ], had an elevated level of 2- O -acetylation [ 41 ]. Together, these findings indicate that TBL32 and TBL33 play a dominant role in mediating 3- O -acetylation of 2- O -GlcA-substituted xylosyl residues and are also involved in xylan 3- O -monoacetylation and 2,3-di- O -acetylation.…”

Section: Resultsmentioning

confidence: 99%

Mutations of Arabidopsis TBL32 and TBL33 Affect Xylan Acetylation and Secondary Wall Deposition

et al. 2016

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Xylan is a major acetylated polymer in plant lignocellulosic biomass and it can be mono- and di-acetylated at O-2 and O-3 as well as mono-acetylated at O-3 of xylosyl residues that is substituted with glucuronic acid (GlcA) at O-2. Based on the finding that ESK1, an Arabidopsis thaliana DUF231 protein, specifically mediates xylan 2-O- and 3-O-monoacetylation, we previously proposed that different acetyltransferase activities are required for regiospecific acetyl substitutions of xylan. Here, we demonstrate the functional roles of TBL32 and TBL33, two ESK1 close homologs, in acetyl substitutions of xylan. Simultaneous mutations of TBL32 and TBL33 resulted in a significant reduction in xylan acetyl content and endoxylanase digestion of the mutant xylan released GlcA-substituted xylooligomers without acetyl groups. Structural analysis of xylan revealed that the tbl32 tbl33 mutant had a nearly complete loss of 3-O-acetylated, 2-O-GlcA-substituted xylosyl residues. A reduction in 3-O-monoacetylated and 2,3-di-O-acetylated xylosyl residues was also observed. Simultaneous mutations of TBL32, TBL33 and ESK1 resulted in a severe reduction in xylan acetyl level down to 15% of that of the wild type, and concomitantly, severely collapsed vessels and stunted plant growth. In particular, the S2 layer of secondary walls in xylem vessels of tbl33 esk1 and tbl32 tbl33 esk1 exhibited an altered structure, indicating abnormal assembly of secondary wall polymers. These results demonstrate that TBL32 and TBL33 play an important role in xylan acetylation and normal deposition of secondary walls.

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Section: Resultsmentioning

confidence: 99%

Mutations of Arabidopsis TBL32 and TBL33 Affect Xylan Acetylation and Secondary Wall Deposition

et al. 2016

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“…Similarly, the acetylation in rwa1 / 2 / 3 / 4 quadruple mutants is most affected at C‐2, according to Lee et al . (). As RWA proteins are not directly involved in acetylation, this result probably reflects an indirect effect.…”

Section: Discussionmentioning

confidence: 97%

“…Accordingly, we found that specific downregulation of both RWA clades in developing Populus wood during the secondary wall formation stage resulted in reductions in wood acetyl contents and xylan acetylation (Figs ). Furthermore, xylan with unsubstituted position C‐2 can be used as a substrate for the Golgi‐residing glucuronyl transferases that apparently compete with acetyl transferases (Yuan et al ., ; Chong et al ., ; Lee et al ., ; Xiong et al ., ). We observed corresponding increases in MeGlcA contents of noncellulosic sugars in plants with reduced RWA expression (Table ), and increased proportions of acetylated (Me)GlcA‐substituted Xyl p residues in DMSO extracts of their xylan (Fig.…”

Section: Discussionmentioning

confidence: 99%

Downregulation of RWA genes in hybrid aspen affects xylan acetylation and wood saccharification

et al. 2017

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High acetylation of angiosperm wood hinders its conversion to sugars by glycoside hydrolases, subsequent ethanol fermentation and (hence) its use for biofuel production. We studied the REDUCED WALL ACETYLATION (RWA) gene family of the hardwood model Populus to evaluate its potential for improving saccharification. The family has two clades, AB and CD, containing two genes each. All four genes are expressed in developing wood but only RWA-A and -B are activated by master switches of the secondary cell wall PtNST1 and PtMYB21. Histochemical analysis of promoter::GUS lines in hybrid aspen (Populus tremula × tremuloides) showed activation of RWA-A and -B promoters in the secondary wall formation zone, while RWA-C and -D promoter activity was diffuse. Ectopic downregulation of either clade reduced wood xylan and xyloglucan acetylation. Suppressing both clades simultaneously using the wood-specific promoter reduced wood acetylation by 25% and decreased acetylation at position 2 of Xylp in the dimethyl sulfoxide-extracted xylan. This did not affect plant growth but decreased xylose and increased glucose contents in the noncellulosic monosaccharide fraction, and increased glucose and xylose yields of wood enzymatic hydrolysis without pretreatment. Both RWA clades regulate wood xylan acetylation in aspen and are promising targets to improve wood saccharification.

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“…Biochemical studies showed that recombinant AXY9 did not exhibit any acetyltransferase activity and it was proposed that AXY9 might act as an intermediate transferring acetyl groups from an acetyl donor to O ‐acetyltransferases responsible for the acetylation of xylan and xyloglucan (Zhong et al ., ). Simultaneous mutations of four Arabidopsis RWA ( reduced wall acetylation ) genes lead to an overall reduction in the acetylation of both xylan and xyloglucan (Lee et al ., , ; Manabe et al ., ) and RNAi downregulation of RWA orthologs in poplar results in a decrease in xylan acetylation (Pawar et al ., ). The RWA proteins contain multiple transmembrane helices but lack the putative acetyltransferase domain found in their fungal homolog, CAS1 (capsule synthesis gene1), which is involved in the acetylation of the capsule polysaccharide glucuronoxylomannan (Gille & Pauly, ).…”

Section: Xylan Biosynthesismentioning

confidence: 99%

Secondary cell wall biosynthesis

2018

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Contents Summary1703I.Introduction1703II.Cellulose biosynthesis1705III.Xylan biosynthesis1709IV.Glucomannan biosynthesis1713V.Lignin biosynthesis1714VI.Concluding remarks1717Acknowledgements1717References1717 Summary Secondary walls are synthesized in specialized cells, such as tracheary elements and fibers, and their remarkable strength and rigidity provide strong mechanical support to the cells and the plant body. The main components of secondary walls are cellulose, xylan, glucomannan and lignin. Biochemical, molecular and genetic studies have led to the discovery of most of the genes involved in the biosynthesis of secondary wall components. Cellulose is synthesized by cellulose synthase complexes in the plasma membrane and the recent success of in vitro synthesis of cellulose microfibrils by a single recombinant cellulose synthase isoform reconstituted into proteoliposomes opens new doors to further investigate the structure and functions of cellulose synthase complexes. Most genes involved in the glycosyl backbone synthesis, glycosyl substitutions and acetylation of xylan and glucomannan have been genetically characterized and the biochemical properties of some of their encoded enzymes have been investigated. The genes and their encoded enzymes participating in monolignol biosynthesis and modification have been extensively studied both genetically and biochemically. A full understanding of how secondary wall components are synthesized will ultimately enable us to produce plants with custom‐designed secondary wall composition tailored to diverse applications.

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Alterations of the degree of xylan acetylation inArabidopsisxylan mutants

Cited by 17 publications

References 23 publications

Mutations of Arabidopsis TBL32 and TBL33 Affect Xylan Acetylation and Secondary Wall Deposition

Mutations of Arabidopsis TBL32 and TBL33 Affect Xylan Acetylation and Secondary Wall Deposition

Downregulation of RWA genes in hybrid aspen affects xylan acetylation and wood saccharification

Secondary cell wall biosynthesis

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