The role of reactive oxygen species in the integration of temperature and light signals.

The remarkable plasticity of the biochemical machinery in plants allows the integration of a multitude of stimuli, enabling acclimation to a wide range of growth conditions. The integration of information on light and temperature enables plants to sense seasonal changes and adjust growth, defense, and transition to flowering according to the prevailing conditions. By now, the role of reactive oxygen species (ROS) as important signaling molecules has been established. Here, we review recent data on ROS as important components in the integration of light and temperature signaling by crosstalk with the circadian clock and calcium signaling. Furthermore, we highlight that different environmental conditions critically affect the interpretation of stress stimuli, and consequently defense mechanisms and stress outcome. For example, day length plays an important role in whether enhanced ROS production under stress conditions is directed towards activation of redox poising mechanisms or triggering programmed cell death (PCD). Furthermore, a mild increase in temperature can cause down-regulation of immunity and render plants more sensitive to biotrophic pathogens. Taken together, the evidence presented here demonstrates the complexity of signaling pathways and outline the importance of their correct interpretation in context with the given environmental conditions.