Arabinosyl deacetylase modulates the arabinoxylan acetylation profile and secondary wall formation

© 2019 ASPB. Acetylation, a prevalent modification of cell-wall polymers, is a tightly controlled regulatory process that orchestrates plant growth and environmental adaptation. However, due to limited characterization of the enzymes involved, it is unclear how plants establish and dynamically regulate the acetylation pattern in response to growth requirements. In this study, we identified a rice (Oryza sativa) GDSL esterase that deacetylates the side chain of the major rice hemicellulose, arabinoxylan. Acetyl esterases involved in arabinoxylan modification were screened using enzymatic assays combined with mass spectrometry analysis. One candidate, DEACETYLASE ON ARABINOSYL SIDECHAIN OF XYLAN1 (DARX1), is specific for arabinosyl residues. Disruption of DARX1 via Tos17 insertion and CRISPR/Cas9 approaches resulted in the accumulation of acetates on the xylan arabinosyl side chains. Recombinant DARX1 abolished the excess acetyl groups on arabinoxylanderived oligosaccharides ofthe darx1mutants invitro. Moreover,DARX1 islocalizedto theGolgiapparatus. Two-dimensional 13C-13C correlation spectroscopy and atomic force microscopy further revealed that the abnormal acetylation pattern observed in darx1 interrupts arabinoxylan conformation and cellulose microfibril orientation, resulting in compromised secondary wall patterning and reduced mechanical strength. This study provides insight into the mechanism controlling the acetylation pattern on arabinoxylan side chains and suggests a strategy to breed robust elite crops

MYB61 is regulated by GRF4 and promotes nitrogen utilization and biomass production in rice

The molecular connection between nitrogen utilization efficiency (NUE) and biomass production is unclear. Here, the authors show that differences in NUE and cellulose biogenesis between rice indica and japonica subspecies can be explained by variation at the MYB61 locus, which is regulated by the NUE regulator GRF4