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