A new acid-labile acetal cross-linker was synthesized and used to prepare protein-loaded hydrogels and microgels. This cross-linker undergoes an acid-catalyzed degradation with a half-life of 5.5 min at pH 5.0 and 24 h at pH 7.4. Protein-loaded hydrogels were synthesized with this cross-linker, and their release profiles were measured as a function of pH. Hydrogels made with the acetal cross-linker release their contents in a pH-dependent manner. The acetal cross-linker was also used to synthesize microgels with sizes between 1 and 10 mum, a range suitable for phagocytosis. The unique acid sensitivity of the acetal cross-linker should make it a useful synthetic intermediate in the design of acid-sensitive drug or gene delivery systems.
These authors contributed equally to this work.
SUMMARYSuccessful reproduction of flowering plants requires constant communication between female tissues and growing pollen tubes. Female cells secrete molecules and peptides as nutrients or guidance cues for fast and directional tube growth, which is executed by dynamic changes of intracellular activities within pollen tubes. Compared with the extensive interest in female cues and intracellular activities of pollen tubes, how female cues are sensed and interpreted intracellularly in pollen is poorly understood. We show here that COBL10, a glycosylphosphatidylinositol (GPI)-anchored protein, is one component of this pollen tube internal machinery. Mutations in COBL10 caused gametophytic male sterility due to reduced pollen tube growth and compromised directional sensing in the female transmitting tract. Deposition of the apical pectin cap and cellulose microfibrils was disrupted in cobl10 pollen tubes. Pollen tube localization of COBL10 at the apical plasma membrane is critical for its function and relies on proper GPI processing and its C-terminal hydrophobic residues. GPI-anchored proteins are widespread cell sensors in mammals, especially during egg-sperm communication. Our results that COBL10 is critical for directional growth of pollen tubes suggest that they play critical roles in cell-cell communications in plants.
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