Prediction of the structures of the plant-specific regions of vascular plant cellulose synthases and correlated functional analysis
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Seed plants express cellulose synthase (CESA) protein isoforms with non-redundant functions, but how the isoforms function differently is unknown. Compared to bacterial cellulose synthases, CESAs have two insertions in the large cytosolic loop: the relatively well-conserved Plant Conserved Region (P-CR) and a Class Specific Region (CSR) that varies between CESAs. Absent any atomic structure of a plant CESA, we used ab initio protein structure prediction and molecular modeling to explore how these plant-specific regions may modulate CESA function. We modeled P-CR and CSR peptides from Arabidopsis thaliana CESAs representing the six clades of seed plant CESAs. As expected, the predicted wild type P-CR structures were similar. Modeling of the mutant P-CR of Atcesa8 R362K (fra6) suggested that changes in local structural stability and surface electrostatics may cause the mutant phenotype. Among CSRs within CESAs required for primary wall cellulose synthesis, the amino sequence and the modeled arrangement of helices was most similar in AtCESA1 and AtCESA3. Genetic complementation of known Arabidopsis mutants showed that the CSRs of AtCESA1 and AtCESA3 can function interchangeably in vivo. Analysis of protein surface electrostatics led to ideas about how the surface charges on CSRs may mediate protein–protein interactions. Refined modeling of the P-CR and CSR regions of GhCESA1 from cotton modified their tertiary structures, spatial relationships to the catalytic domain, and preliminary predictions about CESA oligomer formation. Cumulatively, the results provide structural clues about the function of plant-specific regions of CESA.
KeywordsArabidopsis thaliana Cellulose synthesis Computational protein structure prediction Isoform specificity Mutant complementation
The authors thank Carmen Wilson for her assistance in the generation, propagation, and phenotyping of stable Arabidopsis transformants used in this study.
This work was supported as part of The Center for LignoCellulose Structure and Formation, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences (Award Number DE-SC0001090).
- Case DA et al (2010) AMBER 11. University of California, San FanciscoGoogle Scholar
- Desprez T, Juraniec M, Crowell EF, Jouy H, Pochylova Z, Parcy F, Hofte H, Gonneau M, Vernhettes S (2007) Organization of cellulose synthase complexes involved in primary cell wall synthesis in Arabidopsis thaliana. Proc Natl Acad Sci USA 104:15572–15577. doi: 10.1073/pnas.0706569104 CrossRefGoogle Scholar
- Han J, Kamber M (2006) Data mining: concepts and techniques, 2nd edn. Morgan Kaufmann, San FranciscoGoogle Scholar
- Persson S, Paredez A, Carroll A, Palsdottir H, Doblin M, Poindexter P, Khitrov N, Auer M, Somerville CR (2007) Genetic evidence for three unique components in primary cell-wall cellulose synthase complexes in Arabidopsis. Proc Natl Acad Sci USA 104:15566–15571. doi: 10.1073/pnas.0706592104 CrossRefGoogle Scholar
- Slabaugh E, Sethaphong L, Xiao C, Amick J, Anderson CT, Haigler CH, Yingling YG (2014b) Computational and genetic evidence that different structural conformations of a non-catalytic region affect the function of plant cellulose synthase. J Exp Bot 65:6645–6653. doi: 10.1093/jxb/eru383 CrossRefGoogle Scholar
- Wang J, Howles PA, Cork AH, Birch RJ, Williamson RE (2006) Chimeric proteins suggest that the catalytic and/or C-terminal domains give CesA1 and CesA3 access to their specific sites in the cellulose synthase of primary walls. Plant Physiol 142:685–695. doi: 10.1104/pp.106.084004 CrossRefGoogle Scholar
- Zhou Z (2012) Ensemble methods: foundations and algorithms. Machine learning and pattern recognition. Chapman & Hall/CRC Press, New YorkGoogle Scholar