Abstract
Secreted peptide hormones often contain posttranslationally modified amino acid residues by which their biological activities and receptor binding affinities are highly affected. Posttranslational modifications in peptide hormones in plants so far include tyrosine sulfation, proline hydroxylation and arabinosylation. Tyrosine sulfation is found in PSK and PSY1 peptides and is critical for their function. Recently, we identified tyrosylprotein sulfotransferase (TPST), a key enzyme for tyrosine sulfation, and found that a loss-of-function mutant of AtTPST displayed a marked dwarf phenotype accompanied by stunted roots, reduction in higher order veins and early senescence. Arabinosylation has been found in CLV3, a regulator of stem cell fate. We treated clv3-2 mutant seedlings with purified CLV3 glycopeptide and observed that the clv3-2 SAM treated with CLV3 at 30 nM were substantially reduced in size comparable to wild-type levels. In contrast, synthetic peptide devoid of arabinose showed only weak activity, indicating that the arabinose chain of CLV3 is critical for full activity. Recent progress and future perspective in this research area will be discussed.
