F.A. Razem et al., "The RNA-binding protein FCA is an abscisic acid receptor," Nature, 439:290-4, 2006. (Cited in 82 papers)
Scientists searched for the receptor for abscisic acid hormone in plants for almost 45 years until Robert Hill at the University of Manitoba and colleagues used antibodies to find it. They identified a candidate protein called ABAP1 in barley, and mapped the sequence of that protein in Arabidopsis to the FCA gene, known to be important in flowering.
Abscisic acid regulates stress responses to drought, cold, and high salinity, and could be important for engineering agricultural crops, says lead author Fawzi Razem. "Everyone was expecting that it would be membrane bound," says Hill. However, FCA is a nuclear protein that binds RNA. It's the "first direct example in plants of a hormone affecting RNA splicing," says Razem.
The follow up:
Victor Albert at the University of Oslo says the paper was "extremely important" for his research on FCA as a receptor for external environmental signals. FCA now appears to be only the first in what is now a family of ABA receptors. One Chinese group found that Mg-chelatase H subunit, which is involved in chlorophyll biosynthesis, also binds ABA (Nature 443:823-6, 2006), and another group found a G protein coupled receptor that binds ABA at the plasma membrane (Science, 315:1712-6, 2007).
The next steps:
Hill has turned his focus back to barley and is looking more closely at the original protein that first implicated FCA. He wants to see how ABA affects the FCA-like barley protein involved in dormancy mechanisms, which he says are agriculturally important.
|Effects of ABA binding on receptors:|
|FCA: Delays flowering time in Arabidopsis|
|Mg-chelatase H subunit: Positively regulates seed germination|
|G protein coupled receptor: Mediates dormancy, germination, stomatal closure|