https://orcid.org/0000-0001-8943-6238
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Scott Hayes, Why Do Leaves Rise with the Temperature?, Plant Physiology, Volume 180, Issue 2, June 2019, Pages 691–692, https://doi.org/10.1104/pp.19.00446
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Tropic movement in plants (movement in relation to a directional stimulus) has fascinated thinkers since ancient times (for review, see Whippo and Hangarter, 2006). This interest has led us to a good molecular understanding of how, for example, plants direct their shoots toward light and their roots toward water. However, this is not the only form of movement in plants. Nastic movements occur in response to nondirectional environmental stimuli such as temperature. Warm temperatures promote the raising of leaves in several species (a process termed thermonasty). In comparison with tropic movements, nastic movement in plants is poorly understood. In this issue of Plant Physiology, Park et al. (2019) use an exceptionally broad range of techniques to provide a deep mechanistic insight into how thermonasty occurs in Arabidopsis (Arabidopsis thaliana).
To start with, the researchers confirmed that thermonasty truly is a nastic response and showed that it is independent from directional cues such as light or gravity. Previous studies have shown that the nastic movement of leaves is dependent upon differential growth responses on either side of the petiole (Polko et al., 2012). To gain mechanistic insights, the group focused on differences between the upper (adaxial) and lower (abaxial) sides of the petiole. They found that at warmer temperatures, several auxin-induced genes were induced in the abaxial half of the petiole. This up-regulation was dependent upon the transcription factor PHYTOCHROME INTERACTING FACTOR4 (PIF4), which is required for many aspects of thermomorphogenesis (Koini et al., 2009), and the auxin efflux carrier, PIN-FORMED3 (PIN3).
