Subfunctionalization of phytochrome B1/B2 leads to differential auxin and photosynthetic responses.

Gene duplication and polyploidization are genetic mechanisms that instantly add genetic material to an organism's genome. Subsequent modification of the duplicated material leads to the evolution of neofunctionalization (new genetic functions), subfunctionalization (differential retention of genetic functions), redundancy, or a decay of duplicated genes to pseudogenes. Phytochromes are light receptors that play a large role in plant development. They are encoded by a small gene family that in tomato is comprised of five members: and The most recent gene duplication within this family was in the ancestral gene. Using transcriptome profiling, co-expression network analysis, and physiological and molecular experimentation, we show that tomato and exhibit both common and non-redundant functions Specifically, appears to be the major integrator of light and auxin responses, such as gravitropism and phototropism, while and regulate aspects of photosynthesis antagonistically to each other, suggesting that the genes have subfunctionalized since their duplication.