Calcium-dependent phospholipid-binding proteins in plants : Their characterisation and potential for regulating cell...

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Calcium ions (Ca2+) are known to regulate vesicle-mediated secretion in plant cells.
• The precise molecular mechanisms linking Ca2+ signals to exocytotic responses remain largely unknown.
• A potential link involves Ca2+-dependent phospholipid-binding proteins, such as annexins.

Purpose of the Study:

• To identify and characterize annexin-like proteins in maize (Zea mays L.) coleoptiles.
• To investigate the Ca2+-dependent phospholipid-binding properties of these proteins.
• To explore the potential role of these proteins in regulating plant exocytosis.

Main Methods:

• Isolation of annexin-like proteins from maize coleoptiles using a protocol adapted from animal annexin isolation.
• Analysis of protein molecular weights using SDS-PAGE.
• Liposome-binding assays to assess Ca2+-dependent phospholipid binding.
• Production of antiserum against maize annexins for cross-reactivity studies.

Main Results:

• Identified predominant maize annexin-like proteins with Mr 33000-35000 and a less abundant Mr 23000 protein.
• These proteins bind to acidic phospholipid liposomes in a Ca2+-dependent manner.
• Calcium sensitivity varied between proteins and was influenced by buffer pH.
• Antiserum recognized homologous proteins in other plant species and showed cross-reactivity with chicken Annexin VI.

Conclusions:

• Maize coleoptiles contain annexin-like proteins homologous to animal annexins.
• These proteins exhibit Ca2+-dependent phospholipid binding, suggesting a role in regulating exocytosis.
• The significant effect of pH on Ca2+ binding requirements indicates complex regulatory potential in vivo.