A recently published paper in Neuron (85, 804-818, 2015) elegantly demonstrated that feeding behavior of C. elegans was inhibited by hydrogen peroxide produced by light illumination.1 The authors proposed that photosensitizers, such as riboflavin, could perceive light energy and generate hydrogen peroxide in vivo. Surprisingly, the response of C. elegans to light is very quick and hydrogen peroxide is immediately generated upon illumination (see the Fig. 5 in1). This finding provides important implication for researchers to be careful to consider light response of living organisms. In case of plants, root organs are growing under the ground, and show escape tropism to maintain the root system in darkness.
We have previously reported that primary roots of Arabidopsis seedlings generated reactive oxygen species in root apex region after 10 seconds of blue light illumination.2 Arabidopsis roots speed-up their growth significantly if illuminated. In addition, we also showed that Arabidopsis roots change their physiological aspects to perform the light avoidance over salt stress if kept under light conditions.3 In this respect, the behavior of both C. elegans nematodes and Arabidopsis roots can be considered as light avoidance behavior. Moreover, very similar light avoidance/escape behavior is well-known also for the Drosophila larvae.4,5 It is very intriguing that evolutionarily very distant organisms living in darkness use common signaling factor, reactive oxygen species, to change their behavioral responses under illumination.
Funding
Ken Yokawa was supported by the JSPS (Japanese Society for the Promotion of Science) Postdoctoral Fellowship.
References
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