Phosphorylation is an on/off switch for 5-hydroxyconiferaldehyde O -methyltransferase activity in poplar monolignol biosynthesis

Abstract

Although phosphorylation has long been known to be an important regulatory modification of proteins, no unequivocal evidence has been presented to show functional control by phosphorylation for the plant monolignol biosynthetic pathway. Here, we present the discovery of phosphorylation-mediated on/off regulation of enzyme activity for 5-hydroxyconiferaldehyde O-methyltransferase 2 (PtrAldOMT2), an enzyme central to monolignol biosynthesis for lignification in stem-differentiating xylem (SDX) of Populus trichocarpa. Phosphorylation turned off the PtrAldOMT2 activity, as demonstrated in vitro by using purified phosphorylated and unphosphorylated recombinant PtrAldOMT2. Protein extracts of P. trichocarpa SDX, which contains endogenous kinases, also phosphorylated recombinant PtrAldOMT2 and turned off the recombinant protein activity. Similarly, ATP/Mn 2+ -activated phosphorylation of SDX protein extracts reduced the endogenous SDX PtrAldOMT2 activity by ∼60%, and dephosphorylation fully restored the activity. Global shotgun proteomic analysis of phosphopeptide-enriched P. . PtrAldOMT2 is a homodimeric cytosolic enzyme expressed more abundantly in syringyl lignin-rich fiber cells than in guaiacyl lignin-rich vessel cells. The reversible phosphorylation of PtrAldOMT2 is likely to have an important role in regulating syringyl monolignol biosynthesis of P. trichocarpa.AldOMT | COMT | lignin | phosphoproteomics | phosphoregulation

Phosphorylation of GENOMES UNCOUPLED 4 Alters Stimulation of Mg Chelatase Activity in Angiosperms

“…1B) would significantly alter the function of AtGUN4, as observed for other phosphorylated proteins Willig et al, 2011;Wang et al, 2015). A successful complementation of the white gun4-2 knockout mutant (Supplemental Fig.…”

Breeding maize for silage and biofuel production, an illustration of a step forward with the genome sequence

“…Candidate genes could thus belong to not yet considered gene families involved in other developmental regulation or protein post-translational modifications. It was thus recently shown the role of phosphorylation by calcium-dependent protein kinases (CPK) on COMT activity in poplar [160]. Finally, the underlying determinant of a QTL could also be a regulating factor corresponding to a non-coding genomic sequence, as it was shown for the vgt1 locus in maize [161][162].…”

Lignification of Sheepgrass Internodes at Different Developmental Stages and Associated Alteration of Cell Wall Saccharification Efficiency

“…Indeed, the previous studies have indicated that the ubiquitination and subsequent degradation of PAL can be affected by the Kelch domain-containing F-box proteins in Arabidopsis (Zhang et al, 2013). Moreover, COMT enzyme activity in poplar monolignol biosynthesis can be switched on/off via a phosphorylation-mediated regulation model (Wang et al, 2015). …”