UNASSIGNED: Cellulose synthases (CESAs) synthesize the b-1,4-glucan chains that coalesce to form cellulose microfibrils in plant cell walls. In addition to a large cytosolic (catalytic) domain, CESAs have eight predicted @entity499 ( @entity499 ). However, analogous to the structure of BcsA, a bacterial CESA, predicted TMH5 in CESA may instead be an interfacial helix. This would place the conserved FxVTxK motif in the plant cell cytosol where it could function as a substrate-gating loop as occurs in BcsA. To define the functional importance of the CESA region containing FxVTxK, we tested five parallel mutations in @entity958 @entity55460 and @entity17573 @entity68914 in complementation assays of the relevant cesa mutants. In both organisms, the substitution of the @entity4857 or @entity376 residues in FxVTxK severely affected CESA function. In @entity958 roots, both changes were correlated with lower cellulose anisotropy, as revealed by Pontamine Fast Scarlet. Analysis of hypocotyl inner cell wall layers by atomic force microscopy showed that two altered versions of Atcesa1 could rescue cell wall phenotypes observed in the mutant background line. Overall, the data show that the FxVTxK motif is functionally important in two phylogenetically distant plant CESAs. The results show that @entity17573 provides an efficient model for assessing the effects of engineered CESA mutations affecting primary cell wall synthesis and that diverse testing systems can lead to nuanced insights into CESA structure-function relationships. Although CESA membrane topology needs to be experimentally determined, the results support the possibility that the FxVTxK region functions similarly in CESA and BcsA.

The XXXX and @entity376 residues in the conserved FxVTxK motif are important for the function of phylogenetically distant plant cellulose synthases.

@entity68914 :: ('5921101(Tax:145481)', 'Gene') :: ['CESA5'] @entity499 :: ('MESH:C536217', 'Disease') :: ['transmembrane helices', 'TMHs'] @entity958 :: ('3702', 'Species') :: ['Arabidopsis thaliana', 'Arabidopsis'] @entity55460 :: ('829376(Tax:3702)', 'Gene') :: ['CESA1'] @entity17573 :: ('3218', 'Species') :: ['Physcomitrella', 'Physcomitrella patens'] @entity376 :: ('CHEBI:25094', 'Chemical') :: ['lysine'] @entity4857 :: ('CHEBI:27266', 'Chemical') :: ['valine']
@entity4857 :: (CHEBI:27266,Chemical) :: ['valine']
