CURT1-mediated thylakoid plasticity is required for fine-tuning photosynthesis and plant fitness
Plant Physiology Vol.176, Issue 1Jan 2018
Pribil M, Sandoval-Ibáñez O, Xu W, Sharma A, Labs M, Liu Q, Galgenmüller C, Schneider T, Wessels M, Matsubara S, Jansson S, Wanner G, Leister D

Abstract:
The thylakoid membrane system of higher-plant chloroplasts consists of interconnected subdomains of appressed and non-appressed membrane bilayers, known as grana and stroma lamellae, respectively. The shaping of the cylindrical grana stacks is mediated, in a dosage-dependent manner, by CURT1 protein complexes, which facilitate membrane curvature at the grana margins, the interface between grana and stroma lamellae. Although grana stacks are highly conserved among land plants, the functional relevance of grana stacking remains unclear. Here we show that CURT1-related alteration of thylakoid ultrastructure reduces photosynthetic efficiency and plant fitness under adverse, controlled and natural light conditions. Plants that lack CURT1 are impaired in adjusting grana diameter, which compromises the effectiveness of regulatory mechanisms like PSII repair cycle and state transitions. Interestingly, CURT1A suffices to induce thylakoid membrane curvature in planta, and thylakoid hyper-bending that is observed in CURT1A overexpressor lines. We suggest that CURT1 oligomerisation is regulated at the post-translational level in a light-dependent fashion and CURT1-mediated thylakoid plasticity is critical for plant fitness and plays an important role in fine-tuning photosynthesis under challenging growth conditions.
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