Heping Yang

Peptide signals and their receptors in higher plants

At least four peptides play a vital role in plant cell-cell communication by means of their specific receptors. Two of these receptors have been identified as receptor kinases, which form a large family of receptor molecules in plants. These findings highlight the significance of receptor-mediated peptide signaling in various physiological events in plants, and predict the existence of further peptide-signal-interacting receptor kinases. Some candidates have been found in plant genomes. Here, we outline recent progress and future challenges in the signaling peptide analysis, which began with systemin, phytosulfokine, CLAVATA3 and S-locus cysteine-rich protein (also called S-locus protein 11).

Existence of a plant tyrosylprotein sulfotransferase: novel plant enzyme catalyzing tyrosine O-sulfation of preprophytosulfokine variants in vitro

An in vitro assay system to detect tyrosylprotein sulfotransferase (TPST) activity of higher plant cells was established, using synthetic oligopeptides based on the deduced amino acid sequence of a phytosulfokine‐α (PSK‐α) precursor. TPST activity was found in microsomal membrane fractions of rice, asparagus and carrot cells and it was confirmed that acidic amino acid residues adjacent to the tyrosine residues of acceptor peptides were essential to the sulfation reaction. The asparagus TPST exhibited a broad pH optimum of 7.0–8.5, required manganese ions for maximal activity and appeared to be a membrane‐bound protein localized in the Golgi apparatus. These enzymes should be defined as a new class of plant sulfotransferases that catalyze tyrosine O‐sulfation of a PSK‐α precursor and other unknown proteins.