Negative regulator of cell death and defense responses. Negative regulator of several R genes, including SNC1. May have effects in promoting growth and development. May function in membrane trafficking and in fusion of vesicles with plasma membrane at low temperature. Exhibits calcium-dependent phospholipid binding properties. Interacts (via VWA domain) with BAP1 and BAP2 (PubMed:17631528). Interacts with HSP70-1 and HSP70-2 (PubMed:26408532). Calcium enhances the association with membranes. Expressed in roots and flowers and, at higher levels, in leaves and stems. Strongly expressed in growing tissues. Not detected in green siliques. Down-regulated by high temperature. Up-regulated by pathogen, calcium, low humidity, avirulence gene product avrRpt2 and salicylic acid. The N-terminus (1-116) is sufficient for plasma membrane localization. VWA domain fragments interfere with the function of the full-length protein, triggering a lesion-mimic phenotype. Based on mass spectrometry analysis, the N-peptide must be modified and there might be additional modifications other than myristoylation. Dwarf, twisted leaves and enhanced disease resistance in cv. Columbia when grown at 22 degrees Celsius. No visible phenotype when grown at 28 degrees Celsius, or in cv. Landsberg erecta, cv. No-0, and cv. Wassilewskija at any temperature. Humidity and temperature sensitive lesion mimic phenotype, accelerated hypersensitive response (HR) and increased disease resistance. Bon1 and bon2 double mutants, as well as bon1 and bon3 double mutants are seedling-lethal when grown at 22 degrees Celsius. bon1, bon2 and bon3 triple mutant is seedling-lethal at any temperature. Overexpression of BON1 has no effects on pathogen resistance. Belongs to the copine family.