Recessive-interfering mutations in the gibberellin signaling gene SLEEPY1 are rescued by overexpression of its homologue, SNEEZY.

This article reports the genetic interaction of two F-box genes, SLEEPY1 (SLY1) and SNEEZY (SNE), in Arabidopsis thaliana gibberellin (GA) signaling. The SLY1 gene encodes an F-box subunit of a Skp1-cullin-F-box (SCF) E3 ubiquitin ligase complex that positively regulates GA signaling. The sly1-2 and sly1-10 mutants have recessive, GA-insensitive phenotypes including delayed germination, dwarfism, reduced fertility, and overaccumulation of the DELLA proteins RGA (Repressor of ga1-3), GAI (GA-Insensitive), and RGL2 (RGA-Like 2).

The calcium-dependent protein kinase HvCDPK1 mediates the gibberellic acid response of the barley aleurone through regulation of vacuolar function.

In the aleurone cells of the cereal grain, gibberellic acid (GA) induces the secretion of hydrolases that mobilize endosperm reserves to fuel early seedling growth. GA is known to trigger a range of cellular responses, including increases in cytoplasmic calcium, vacuolar reserve mobilization, gene transcription, and the synthesis and secretion of hydrolases. To further define elements of the Ca2+-dependent GA response machinery, we have cloned a Ca2+-dependent protein kinase (HvCDPK1) from these cells.

From common signalling components to cell specific responses: insights from the cereal aleurone.

Studies into the molecules underlying plant signal transduction events continue to reveal the involvement of highly conserved factors such as Ca2+, calmodulin, cyclic GMP and phospholipases in a remarkably diverse array of physiological processes. The hormonal response systems in the aleurone cells of the cereal grain and in the stomatal guard cell are beginning to reveal how diversity of response can be hard wired into these cells despite the use of these common signalling intermediates. In both the aleurone and the guard cell ABA signalling operates through the action of phospholipase D and alterations in a Ca2+-dependent signalling system.

Gibberellins: regulating genes and germination.

The range of processes regulated by gibberellins (GAs) covers all aspects of the life history of the plant from seed germination to vegetative growth and flowering. In seeds there has been an intensive search, using the techniques of both biochemistry and cell biology, for the regulatory molecules linking GA perception to gene regulation and the events of germination. Although a GA receptor has yet to be identified, the site of perception has been localized to the plasma membrane.