Hemsley, P. A. | Search bioRxiv

bioRxiv2026

Arabidopsis GHL1 is an orthologue of Hedgehog acyl transferase but likely catalyses GPI-anchor remodelling rather than peptide acylation.

The GUP1/HHAT family of MBOAT proteins have been implicated in GPI-anchor acyl-chain remodelling in fungi and secreted peptide acylation in eumetazoans, but whether these activities are distinct or GUP1/HHAT proteins are bifunctional has not been addressed. We show that the GUP1/HHAT family form a distinct orthologous clade within eukaryotes with structural homology, suggesting a single evolutionary event for their origin and common mode of action. Arabidopsis plants homozygous for loss of GUP1/HHAT-like activity cannot be recovered suggesting that loss is lethal, and further examination suggests that there are severe effects on transmission through the male gamete. Recent work suggests that rice GUP1-like BC16 is a GPI-anchor acyl-chain remodelase, but a potential role for non-eumetazoan GUP1 and HHAT-like proteins in secreted peptide acylation has not been assessed. By reconstituting HHAT peptide acyl transferase activity towards Hedgehog-like peptides in plants we demonstrate that Arabidopsis GUP1/HHAT-like proteins likely do not possess appreciable HHAT-like peptide acyltransferase activity. However, through this work we provide a novel means for cell surface display of proteins in eukaryotic systems, demonstrating that the minimal acyl-acceptor peptide sequence of Hedgehog morphogens, when expressed alongside HHAT, allows for immobilisation of proteins in the outer leaflet of the plasma membrane via their N-terminus, rather than the C-terminus as is the case for traditional GPI-anchor mediated cell surface display.

plant biology↗

bioRxiv2019

Juxta-membrane S-acylation of plant receptor-like kinases - fortuitous or functional?

S-acylation is a common post-translational modification of membrane protein cysteine residues with many regulatory roles. S-acylation adjacent to transmembrane domains has been described in the literature as affecting diverse protein properties including turnover, trafficking and microdomain partitioning. However, all of these data are derived from mammalian and yeast systems. Here we examine the role of S-acylation adjacent to the transmembrane domain of the plant pathogen perceiving receptor-like kinase FLS2. Surprisingly, S-acylation of FLS2 adjacent to the transmembrane domain is not required for either FLS2 trafficking or signalling function. Expanding this analysis to the wider plant receptor-like kinase superfamily we find that S-acylation adjacent to receptor-like kinase domains is common but poorly conserved between orthologues through evolution. This suggests that S-acylation of receptor-like kinases at this site is likely the result of chance mutation leading to cysteine occurrence. As transmembrane domains followed by cysteine residues are common motifs for S-acylation to occur, and many S-acyl transferases appear to have lax substrate specificity, we propose that many receptor-like kinases are fortuitously S-acylated once chance mutation has introduced a cysteine at this site. Interestingly some receptor-like kinases show conservation of S-acylation sites between orthologues suggesting that S-acylation has come to play a role and has been positively selected for during evolution. The most notable example of this is in the ERECTA-like family where S-acylation of ERECTA adjacent to the transmembrane domain occurs in all ERECTA orthologues but not in the parental ERECTA-like clade. This suggests that ERECTA S-acylation occurred when ERECTA emerged during the evolution of angiosperms and may have contributed to the neo-functionalisation of ERECTA from ERECTA-like proteins.

plant biology↗