From “Botany: Moonlighting Enzyme Works Double Shift 24/7” (ScienceDaily, Jan. 31, 2012), we learn ,
A team of researchers led by Michigan State University has discovered an overachieving plant enzyme that works both the day and night shifts.
The discovery, featured in the current issue of Proceedings of the National Academies of Science, shows that plants evolved a new function for this enzyme by changing merely one of its protein building blocks.
Evolved a new function?
In arabadopsis, the much-studied mustard plant, the enzyme ATP synthase plays a daytime role in storing energy from photosynthesis. At night, it transports energy to the roots. One of the enzyme’s components has two forms, one filling each function:
The building block on which the researchers focused is called gamma, a component of ATP synthase. There are two forms of gamma, gamma-1 and gamma-2. When researchers removed gamma-1, photosynthesis was completely stopped. When gamma-2 was removed, the plant could not make normal root hairs (the part of the root that takes up nutrients.)
Some friends’ baloney meters shorted out, and they asked, what does “evolved a new function” mean here?
The concept of evolution is time-dependent. The parent function precedes the daughter function. Which is which? Energy is produced before it is stored – but it must be stored when it is produced. One friend remarked, “I see no ‘evolution’ here. The more sensible inference is that this enzyme’s dual role was designed that way.”
One way of putting it: The plant enzyme “was evolved” to do both functions at once.