The endopeptidases （EPs） in wheat endosperm during seed germination and subsequent seedling growth were characterized by gradient-polyacrylamide gel electrophoresis with gelatin copolymerized into the gel. Four cyst...The endopeptidases （EPs） in wheat endosperm during seed germination and subsequent seedling growth were characterized by gradient-polyacrylamide gel electrophoresis with gelatin copolymerized into the gel. Four cysteine EPs （EP1, EP2, EP3 and EP4） were detected in wheat endosperm during the 7 d growth after seed imbibition. The results also showed that the activities of all of these EPs increased continuously, and EP2 first appeared and had the highest proteolytic activity among the four EPs in this experimental process. The optimum pH and temperature of all four EPs were 4.0 and 40.0 ~C. All EPs were completely inhibited by 25 μmol/L E-64 and had no good thermal stabilities, especially EP1. In addition, these EPs had different substrate specificities to albumins, globulins, gliadins and glutenins; the main storage proteins of mature wheat endosperm. Among them, EP2 had the highest proteolytic activities on globulins, gliadins and glutenins, and might be the most important and specific EP with potential to be tightly correlated with seedling development.展开更多
Extensins （EXTs） are highly repetitive plant O-glycoproteins that require several post-translational modifi- cations （PTMs） to become functional in plant cell walls. First, they are hydroxylated on contiguous prol...Extensins （EXTs） are highly repetitive plant O-glycoproteins that require several post-translational modifi- cations （PTMs） to become functional in plant cell walls. First, they are hydroxylated on contiguous proline residues; then they are O-glycosylated on hydroxyproline and serine. After secretion into the apoplast, O-glycosylated EXTs form a tridimensional network organized by inter- and intra-Tyr linkages. Recent studies have made significant progress in the identification of the enzymatic machinery required to process EXTs, which includes prolyl 4-hydroxylases, glycosyltransferases, papain-type cysteine endopeptidases, and peroxidases. EXTs are abundant in plant tissues and are particularly important in rapidly expanding root hairs and pollen tubes, which grow in a polar manner. Small changes in EXT PTMs affect fastgrowing cells, although the molecular mechanisms underlying this regulation are unknown. In this review, we highlight recent advances in our understanding of EXT modifications throughout the secretory pathway, EXT assembly in cell walls, and possible sensing mechanisms involving the Catharanthus roseus cell surface sensor receptor-like kinases located at the interface between the apoplast and the cytoplasmic side of the plasma membrane.展开更多
基金Supported by the National Natural Science Foundation of China (30370851).
文摘The endopeptidases （EPs） in wheat endosperm during seed germination and subsequent seedling growth were characterized by gradient-polyacrylamide gel electrophoresis with gelatin copolymerized into the gel. Four cysteine EPs （EP1, EP2, EP3 and EP4） were detected in wheat endosperm during the 7 d growth after seed imbibition. The results also showed that the activities of all of these EPs increased continuously, and EP2 first appeared and had the highest proteolytic activity among the four EPs in this experimental process. The optimum pH and temperature of all four EPs were 4.0 and 40.0 ~C. All EPs were completely inhibited by 25 μmol/L E-64 and had no good thermal stabilities, especially EP1. In addition, these EPs had different substrate specificities to albumins, globulins, gliadins and glutenins; the main storage proteins of mature wheat endosperm. Among them, EP2 had the highest proteolytic activities on globulins, gliadins and glutenins, and might be the most important and specific EP with potential to be tightly correlated with seedling development.
文摘Extensins （EXTs） are highly repetitive plant O-glycoproteins that require several post-translational modifi- cations （PTMs） to become functional in plant cell walls. First, they are hydroxylated on contiguous proline residues; then they are O-glycosylated on hydroxyproline and serine. After secretion into the apoplast, O-glycosylated EXTs form a tridimensional network organized by inter- and intra-Tyr linkages. Recent studies have made significant progress in the identification of the enzymatic machinery required to process EXTs, which includes prolyl 4-hydroxylases, glycosyltransferases, papain-type cysteine endopeptidases, and peroxidases. EXTs are abundant in plant tissues and are particularly important in rapidly expanding root hairs and pollen tubes, which grow in a polar manner. Small changes in EXT PTMs affect fastgrowing cells, although the molecular mechanisms underlying this regulation are unknown. In this review, we highlight recent advances in our understanding of EXT modifications throughout the secretory pathway, EXT assembly in cell walls, and possible sensing mechanisms involving the Catharanthus roseus cell surface sensor receptor-like kinases located at the interface between the apoplast and the cytoplasmic side of the plasma membrane.
