Abstract
Calcium and reactive oxygen species (ROS) are two of the earliest second messengers in response to environmental stresses in plants. The rise and sequestration of these messengers in the cytosol and apoplast are formed by various channels, transporters, and enzymes that are required for proper defense responses. It remains unclear how calcium and ROS signals regulate each other during pattern-triggered immunity (PTI). In the present study, we examined the effects of perturbing one signal on the other in Arabidopsis leaves upon the addition of flg22, a well-studied microbe-associated molecular pattern (MAMP). To this end, a variety of pharmacological agents were used to suppress either calcium or ROS signaling. Our data suggest that cytosolic calcium elevation is required to initiate and regulate apoplastic ROS production generated by respiratory burst oxidase homologs (RBOHs). In contrast, ROS has no effect on the initiation of the calcium signal, but is required for forming a sufficient amplitude of the calcium signal. This finding using pharmacological agents is corroborated by the result of using a genetic double mutant, rbohd rbohf. Our study provides an insight into the mutual interplay of calcium and ROS signals during the MAMP-induced PTI response in plants.
Highlights
Plants, like all organisms, depend on the ability to perceive and respond to environmental challenges
Cytosolic calcium was still increased dependent on the dose of flg22 applied, the intensity of the response was slightly weakened in the rbohd/f mutant in comparison to the wild type plants (Figure 4A,C; Supplementary Figures S10 and S11). These results suggests that initiation of cytosolic calcium elevation upon flg22 addition was independent of apoplastic reactive oxygen species (ROS) signal produced by respiratory burst oxidase homologs (RBOHs)
RBOHs are a central hub for the interplay during calciumdependent ROS signaling
Summary
Like all organisms, depend on the ability to perceive and respond to environmental challenges. Discriminating between the myriad of different stresses that plants are exposed to is dependent on signaling systems based around second messenger molecules. The second messengers rise in concentration in the cytosol and apoplast and are quickly sequestered due to their often toxic nature, making them excellent signaling molecules [1,2,3]. It has been observed that different stimuli often produce a unique rise and fall in the concentration of secondary massagers, dubbing them “signatures” [3]. Each signature dynamics must be unperturbed for the plant to invoke the correct response to environmental stresses [4]
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