Abstract
Regulation of light absorption under variable light conditions is essential to optimize photosynthetic and acclimatory processes in plants. Light energy absorbed in excess has a damaging effect on chloroplasts and can lead to cell death. Therefore, plants have evolved protective mechanisms against excess excitation energy that include chloroplast accumulation and avoidance responses. One of the proteins involved in facilitating chloroplast movements in Arabidopsis thaliana is the J domain-containing protein required for chloroplast accumulation response 1 (JAC1). The function of JAC1 relates to the chloroplast actin filaments appearance and disappearance. So far, the role of JAC1 was studied mainly in terms of chloroplasts photorelocation. Here, we demonstrate that the function of JAC1 is more complex, since it influences the composition of photosynthetic pigments, the efficiency of photosynthesis, and the CO2 uptake rate. JAC1 has positive effect on water use efficiency (WUE) by reducing stomatal aperture and water vapor conductance. Importantly, we show that the stomatal aperture regulation is genetically coupled with JAC1 activity. In addition, our data demonstrate that JAC1 is involved in the fine-tuning of H2O2 foliar levels, antioxidant enzymes activities and cell death after UV-C photooxidative stress. This work uncovers a novel function for JAC1 in affecting photosynthesis, CO2 uptake, and photooxidative stress responses.
Highlights
Plants regulate the light absorption under naturally variable conditions, which is essential for photosynthesis optimization and acclimation
Under light induction cp-actin filaments relocalize to the leading edge of chloroplasts and cause chloroplast movement that is regulated by both phot1 and phot2 (Kadota et al, 2009), and by a J-domain protein required for chloroplast accumulation response 1 (JAC1) (Ichikawa et al, 2011)
Since JAC1 is involved in the regulation of chloroplast movements (Supplementary Figure 1), our first aim was to assess if it has an influence on photosynthetic efficiency
Summary
Plants regulate the light absorption under naturally variable conditions, which is essential for photosynthesis optimization and acclimation. Light energy absorbed in excess (excess excitation energy, EEE) leads to photoinhibition and chloroplast retrograde-signalling and may cause chloroplast damage and cell death Plants have evolved EEE avoidance and dissipation mechanisms to ensure the proper functionality of the photosynthetic apparatus and photosynthesis. One of these mechanisms is chloroplast movement (Demarsy et al, 2018). Under light induction cp-actin filaments relocalize to the leading edge of chloroplasts and cause chloroplast movement that is regulated by both phot and phot (Kadota et al, 2009), and by a J-domain protein required for chloroplast accumulation response 1 (JAC1) (Ichikawa et al, 2011)
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