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. The article by Guerriero et al., places in perspective, a potential role of WDR proteins in the biosynthesis and regulation of plant cell wall formation. They propose that, because in plants the formation of lignocellulosic biomass involves extensive synthesis of cell wall polysaccharides, which also requires the assembly of large transmembrane enzyme complexes, intensive vesicle trafficking, interactions with the cytoskeleton, and coordinated gene expression, WDR proteins could participate in these processes. They mention that, by experimental approaches in Arabidopsis thaliana, three WDR proteins have been linked to the cell wall, whereas significantly more potential candidates linked to cell wall-related processes in A. thaliana have been obtained by in silico analysis. They also suggest a relationship based on the frequent observation of WDR and cell wall synthetic gene collinearity. Finally, they discuss the prospects of biotechnological engineering for enhanced biomass production. The research article by Huang et al., shows that two pathways, …