Thursday, December 11, 2008

Gibberellin-induced DELLA recognition by the gibberellin receptor GID1


Now there's title for you. I bet you can't wait to read this post. Well, not to worry, the title is that of a featured article in the current issue of Nature, by a team researchers in Japan and North Carolina. Here is the abstract:
Gibberellins control a range of growth and developmental processes in higher plants and have been widely used in the agricultural industry. By binding to a nuclear receptor, GIBBERELLIN INSENSITIVE DWARF1 (GID1), gibberellins regulate gene expression by promoting degradation of the transcriptional regulator DELLA proteins, including GIBBERELLIN INSENSITIVE (GAI). The precise manner in which GID1 discriminates and becomes activated by bioactive gibberellins for specific binding to DELLA proteins remains unclear. Here we present the crystal structure of a ternary complex of Arabidopsis thaliana GID1A, a bioactive gibberellin and the amino-terminal DELLA domain of GAI. In this complex, GID1A occludes gibberellin in a deep binding pocket covered by its N-terminal helical switch region, which in turn interacts with the DELLA domain containing DELLA, VHYNP and LExLE motifs. Our results establish a structural model of a plant hormone receptor that is distinct from the mechanism of the hormone perception and effector recognition of the known auxin receptors.
Gibberish? I haven't a clue what the article is about, but I love scanning this stuff every week, and feasting my eyes on the colorful schematic diagrams of fabulously twisty molecules. It's one thing to look at a grain of rice. It's something else altogether to have a sense of what's going on inside that tiny package -- a buzz of molecular machinery as complex as a massive oil refinery.

For important articles like this, Nature will often provide a "News & Views" summary in slightly more commonplace English. We learn, for example, that "gibberellins (GAs) promote plant growth and development processes, such as seed germination and flower induction. Their action allows plants to respond to changes in their environment. At the molecular level, they stimulate the destruction of growth represssing proteins." The more immediately relevant story is that the so-called "green revolution" in global food production depends crucially on understanding the molecular signaling systems that are busily at work in every rice grain -- and other plants.

It's hard to know what to marvel at more -- the astonishingly complex molecular machinery of life, or the cunning of the human brain that reveals this microscopic machinery for our appreciation and utilization.