Light as a signal
Phytochromes (red/far-red) and cryptochromes (blue light) trigger massive transcriptional reprogramming when seedlings emerge from soil or when shade is detected.
Key regulated processes
- Chlorophyll biosynthesis genes
- Photosystem assembly (PSA, PSB genes)
- Carbon fixation enzymes (Rubisco small subunit)
- Shade avoidance (elongation genes under low R:FR ratio)
Experimental approaches
qPCR measures single-gene expression; RNA-seq profiles thousands of genes under light treatments. Reporter lines (GUS/GFP fused to promoters) visualize expression in tissue.