Nat Commun.: auth.: group Fankhauser

Nat Commun. 2022 Oct 10;13(1):5659. doi: 10.1038/s41467-022-33384-9.

A combination of plasma membrane sterol biosynthesis and autophagy is required for shade-induced hypocotyl elongation

Yetkin Çaka Ince 1Johanna Krahmer 1Anne-Sophie Fiorucci 1Martine Trevisan 1Vinicius Costa Galvão 1Leonore Wigger 2Sylvain Pradervand 2Laetitia Fouillen 3Pierre Van Delft 3Manon Genva 3 4Sebastien Mongrand 3Hector Gallart-Ayala 5Julijana Ivanisevic 5Christian Fankhauser 6


Plant growth ultimately depends on fixed carbon, thus the available light for photosynthesis. Due to canopy light absorption properties, vegetative shade combines low blue (LB) light and a low red to far-red ratio (LRFR). In shade-avoiding plants, these two conditions independently trigger growth adaptations to enhance light access. However, how these conditions, differing in light quality and quantity, similarly promote hypocotyl growth remains unknown. Using RNA sequencing we show that these two features of shade trigger different transcriptional reprogramming. LB induces starvation responses, suggesting a switch to a catabolic state. Accordingly, LB promotes autophagy. In contrast, LRFR induced anabolism including expression of sterol biosynthesis genes in hypocotyls in a manner dependent on PHYTOCHROME-INTERACTING FACTORs (PIFs). Genetic analyses show that the combination of sterol biosynthesis and autophagy is essential for hypocotyl growth promotion in vegetative shade. We propose that vegetative shade enhances hypocotyl growth by combining autophagy-mediated recycling and promotion of specific lipid biosynthetic processes.