TRICHOME BIREFRINGENCEand Its HomologAT5G01360Encode Plant-Specific DUF231 Proteins Required for Cellulose Biosynthesis in Arabidopsis    

Abstract

The Arabidopsis (Arabidopsis thaliana) trichome birefringence (tbr) mutant has severely reduced crystalline cellulose in trichomes, but the molecular nature of TBR was unknown. We determined TBR to belong to the plant-specific DUF231 domain gene family comprising 46 members of unknown function in Arabidopsis. The genes harbor another plant-specific domain, called the TBL domain, which contains a conserved GDSL motif known from some esterases/lipases. TBR and TBR-like3 (TBL3) are transcriptionally coordinated with primary and secondary CELLULOSE SYNTHASE (CESA) genes, respectively. The tbr and tbl3 mutants hold lower levels of crystalline cellulose and have altered pectin composition in trichomes and stems, respectively, tissues generally thought to contain mainly secondary wall crystalline cellulose. In contrast, primary wall cellulose levels remain unchanged in both mutants as measured in etiolated tbr and tbl3 hypocotyls, while the amount of esterified pectins is reduced and pectin methylesterase activity is increased in this tissue. Furthermore, etiolated tbr hypocotyls have reduced length with swollen epidermal cells, a phenotype characteristic for primary cesa mutants or the wild type treated with cellulose synthesis inhibitors. Taken together, we show that two TBL genes contribute to the synthesis and deposition of secondary wall cellulose, presumably by influencing the esterification state of pectic polymers.

The use of FTIR spectroscopy to monitor modifications in plant cell wall architecture caused by cellulose biosynthesis inhibitors

“…6 The use of PCA in conjunction with FTIR spectroscopy has proved to be an important tool in the study of cell wall structure and composition heterogeneity in a species, 7,8 or among different species, 5,9-11 as well as in the identification and classification of mutants with altered cell wall compositions. 6,[12][13][14] This approach has been also very useful in the characterization of the modifications appearing in this kind of mutants [15][16][17][18][19][20] or in transgenic plants with altered cell walls 21 and in the modifications to cell wall composition induced by different biotic or abiotic stress factors.…”

The Two DUF642 At5g11420 and At4g32460-Encoded Proteins Interact In Vitro with the AtPME3 Catalytic Domain

“…DUF231 is present in the proteins of the TRICHOME BIREFRINGENCE/TRICHOME BIREFRINGENCE-LIKE (TBR/TBL) plant family with 46 members in Arabidopsis. The role of this family in cellulose biosynthesis has been recently described; tbr mutants presented decreased levels of crystalline secondary wall cellulose in trichomes and stems (Bischoff et al, 2010a). Loss of TBR also results in increased PME activity and reduced pectin esterification, which suggests that TBL/DUF231 proteins are "bridging" proteins that crosslink different cell wall networks (Bischoff et al, 2010b).…”

Two Trichome Birefringence-Like Proteins Mediate Xylan Acetylation, Which Is Essential for Leaf Blight Resistance in Rice

“…1), which were shown to affect xylan acetylation without enzymatic characterization (Yuan et al, 2016b). OsTBL1 and OsTBL2 have canonical TBL structures, including a TM domain at the N terminus and a TBL domain and a DUF231 domain containing the GDS and DxxH motifs, respectively (Bischoff et al, 2010;Gille and Pauly, 2012;Supplemental Fig. S1).…”

“…The decrease in acetylation level on multiple polymers such as XyG and xylan in the axy9 mutant indicates its involvement in O-acetylation, but its precise function remains elusive (Schultink et al, 2015). TBL proteins share two conserved domains, the TBL and DUF231 domain, with the Arabidopsis Trichome Birefringence protein (Potikha and Delmer, 1995;Bischoff et al, 2010). Each domain harbors one conserved motif, a Gly-Asp-Ser (GDS) and an Asp-x-x-His (DxxH), respectively (Gille and Pauly, 2012).…”