Life on Earth is fueled by the 'relationship' between plants and sunlight. A new research made on Arabidopsis, a common model plant employed in researches and published in Nature "has significantly advanced our understanding of how plant responses to light are regulated, and perhaps even how such responses evolved," said Michael Mishkind, a program director at the National Science Foundation (NSF).

The plants seem to prepare themselves to respond to light while still in the dark, by synthesizing a couple of closely related proteins (FHY3 and FAR1) that boost the synthesis of other two closely related proteins (FHY1 and FHL), essential factors involved in the plant's reaction to light.

"The plant probably stockpiles these proteins needed for light responses in the dark for the same reason that a traveler fills his car's gas tank the night before a morning journey: in order to be able to get going, without delay, at first light." said co-author Haiyang Wang, a member of the research team from Boyce Thompson Institute for Plant Research.

The plant reacts to light first through light-sensing pigment proteins named phytochrome A, found in the cytoplasm cell and reacting to red light. Light changes the shape of phytochrome A, which permits it to attach to FHY1 and FHL, causing a storing of phytochrome A in the cell nucleus. The activated phytochrome A turns on genes from the nuclear DNA involved in plant growth, flowering, straining and development.

This has been already known, but the FHY3 and FAR1 connection to reaction to light is a novelty.

The team also found a negative feedback loop between accumulations of phytochrome A in the cell nucleus and the levels of FHY3 and FAR1 proteins: as more phytochrome A is found in the nucleus, less FHY3 and FAR1 proteins are synthesized, and so less phytochrome A enters the nucleus.

"This feedback loop serves as a built-in brake that limits the flow of light responses," said Wang.

FHY3 and FAR1 proteins resemble some enzymes encoded by mobile DNA stretches named "jumping genes." (which can translate between various locations in a cell's DNA). In fact, FHY3 and FAR1 could have evolved from the jumping gene material.

"If indeed the proteins did so, this important chapter in evolution may have helped make possible the establishment of flowering plants on earth," said Wang.