Editorial: Signaling through WD-Repeat Proteins in Plants.

Plants are sessile organisms that rely on appropriate signal-transduction responses in order to cope with the challenges imposed by their environment, and must be able to recognize potential damage or benefit to respond accordingly. These response mechanisms are mediated by specific sets of signal receptors, effector proteins interacting through scaffolding assemblies, second messengers, and transcription factors, among other components. The specific responses occur through protein–protein interactions conveyed by particular sequence modules such as the WD-repeat (WDR), which has been evolutionarily conserved in many proteins participating in signaling events. This module consists of a sequence that spans a number of conserved amino acids and ends with tryptophan and aspartate (WD) residues (Neer et al., 1994). The WDR proteins comprise a breathtakingly diverse superfamily of regulatory proteins, representing a breadth of biochemical mechanisms and cellular processes (van Nocker and Ludwig, 2003). One particular variant, the WD40 domain, starts with glycine and histidine followed by a 40 amino acid stretch that ends with WD. These domains usually assemble into β-stranded platforms that form a structure called the β-propeller (Wang et al., 2013). Through the interactions on various parts of the platform, signal-transduction molecules are brought in close proximity to relay conformational changes or enzyme-mediated modifications. The topic “Signaling through WD-repeat proteins in plants” consists of two comprehensive reviews, a perspective, and two articles of original research on the field that help understand how some of these WDR proteins from plants interact with other molecules in response to particular signals.