Confers resistance to low temperatures by limiting chloroplast damage and cell death, thus maintaining growth homeostasis (PubMed:16667557, PubMed:23617639, PubMed:23651299). Regulates steryl-esters and sterols accumulation (PubMed:16667557). Limits leaf necrosis associated with virulent bacterial infection (e.g. Pseudomonas syringae pv. tomato DC3000) (PubMed:23617639). H2O + NAD(+) = ADP-D-ribose + H(+) + nicotinamide Mostly expressed in leaves and flowers (mainly in sepals), and, at a lower intensity, in stems (PubMed:23617639, PubMed:23651299). Present at low levels in roots and seeds (PubMed:23617639). Stabilized by low temperatures (at protein level). The TIR domain mediates NAD(+) hydrolase (NADase) activity. Self-association of TIR domains is required for NADase activity. RNAi lines display chilling sensitivity. Massive necrotic response to virulent Pseudomonas syringae pv. tomato infection, but normal bacterial proliferation.