ROS Signaling

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• ROS Signaling
• Toxic but also participate in signaling
  events
• ROSReacive oxygen species
• ROI Reactive oxygen intermediates
• Source
• 1. an unavoidable byproducts of aerobic
  metabolism
• 2. abiotic stresses glycoxylate oxidase
  in peroxisomes during
• photorespiration, etc.
• 3. NADPH oxidases, amine oxidases and
  cell-wall-bound peroxidase
• Concentration
• 1. 240?MS-1O2- and a steady state
  level of 0.5?M H2O2 in chloroplast.
• 2. 240-270 ?MS-1O2- and a
  steady-state level of 5-15 ?MH2O2 in
• drought stress and
  dessication, salt stress, chilling, heat shock,
• heavy metals, ultraviolet
  radiation, air pollutants such as ozone and
• SO2, mechanical stress,
  nutrient deprivation, pathogen attack and
• high light stress.
• Significance
• 1. cellular indicators of stress
• 2. secondary messengers involved
  in the stress-response signal

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Reactive Oxygen Species

• Drought, salt, and cold stress all induce the
  accumulation of ROS such as superoxide, hydrogen
  peroxide, and hydroxyl radicals.
• ABA was shown to induce H2O2 production, ROS may
  be intermediate signals for ABA in mediating
  Catalase 1 gene (CAT1) expression,
  thermotelerance , activation of Ca2 channels in
  guard cells closure, and even ABA biosynthesis.
• These ROS may be signals inducing ROS scavengers
  and other protective mechanisms.---higher ROS
  scavenging ability show increased tolerance to
  environmental stresses.
• Some genes related to osmotic stress signaling
  have been shown to be upregulated by oxidative
  stress, including the transcription factor DREB2A
  .

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