Signaling events in plants: Stress factors in combination change the picture

• Drought and heat signalling in plants is summarized briefly.
• Combined abiotic stress display different gene expression patterns compared to single stress.
• Biotic and abiotic stress factors in combination strongly influence each other.

Being sessile organisms, plants are constantly exposed to various kinds of environmental stimuli. To survive under unfavorable environmental conditions they have evolved strategies to allow a balance between growth, reproduction and survival. In this review article, we first focus on two major abiotic stress factors, drought and heat, and briefly summarize the current knowledge on signal transduction pathways involved in plant responses to these stresses. In nature it is unlikely that plants are exposed to abiotic or biotic stresses in isolation. Hence, multiple stress situations are more likely to occur including heat, drought, salinity and pathogen attack. Since in many cases stress responses are antagonistic, predictions of molecular responses to multiple stresses based on single stress data is difficult or even impossible. Only recently, researchers started to study multiple-stress interactions and discovered for instance that plant responses to a combination of heat and drought differ from those to both single stresses. Moreover, abiotic stress applications are likely to influence plant-pathogen interactions and vice versa. Here, we discuss various aspects of multiple stress applications published within the last few years and pronounce the importance to study biotic and abiotic stress combinations in order to predict plant responses to future climate changes.