Salicylic acid glucoside acts as a slow inducer of oxidative burst in tobacco suspension culture.
Salicylic acid beta-glucoside (SAG) is a storage form of a defense signal against pathogens, releasing free salicylic acid (SA), to meet the requirements in plants. Since excess SA induces locally restricted cell death following oxidative burst and Ca2+ influx in plants, the effects of SAG on cell viability, Ca2+ influx, and generation of superoxide (O2*-) were examined in suspension-cultured tobacco BY-2 cells expressing aequorin. Among SA-related chemicals tested, only SAG induced the slow and long-lasting O2*- generation, although SAG was less active in acute O2*- generation, Ca2+ influx and induction of cell death. The prolonging action of SAG is likely due to gradual release of SA and the data suggested that a peroxidase-dependent reaction is involved. Notably, pretreatment with low-dose SA (50 micromu) enhanced the response to SAG by 2.5-fold. There are four possible secondary messengers in early SA signaling detectable in the BY-2 culture, namely O2*-, H2O2, Ca2+ and protein kinase (PK). If these messengers are involved in the low-dose SA-dependent priming for SAG response, they should be inducible by low-dose SA. Among the four SA-inducible signaling events, PK activation was excluded from the low-dose SA action since a much higher SA dose (> 0.4 mmu) was required for PK activation.
Kawano
Tomonori
T
Graduate School of Environmental Engineering, The University of Kitakyushu, Kitakyushu 808-0157, Japan. kawanotom@env.kitakyu-u.ac.jp
Tanaka
Shigeo
S
Kadono
Takashi
T
Muto
Shoshi
S
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005960:Glucosides / Q000494:pharmacology*; D007700:Kinetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000187:drug effects* / Q000502:physiology; D012459:Salicylates / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013481:Superoxides / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
D005960:Glucosides; D017382:Reactive Oxygen Species; D012459:Salicylates; C084746:salicylic acid glucoside; D013481:Superoxides; D002118:Calcium