ABSTRACT
The CLAVATA (CLV) signaling pathway is essential for shoot meristem homeostasis in Arabidopsis. CLV acts to limit the expression domain of the stem cell-promoting gene WUSCHEL (WUS). The closely related receptor-kinases CLV1 and BAM1 are key components in this pathway; however, the downstream factors that link the receptors to WUS regulation are poorly understood. The Arabidopsis gene At5g65480 was recently identified as a direct transcriptional target up-regulated by WUS. We have independently identified this gene which we term CCI1 as a CLV1 and BAM1 interacting protein in vitro and in transient expression. CCI1 has phosphatidylinositide-binding activity in vitro and localizes to the plasma membrane in transient expression. Furthermore, CLV signaling components and CCI1 both partition to detergent-resistant membrane microdomains characterized as lipid rafts.
Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , Homeodomain Proteins/metabolism , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Gene Expression Regulation, Plant/genetics , Gene Expression Regulation, Plant/physiology , Homeodomain Proteins/genetics , Signal Transduction/genetics , Signal Transduction/physiologyABSTRACT
The RLK/Pelle class of proteins kinases is composed of over 600 members in Arabidopsis. Many of the proteins in this family are receptor-like kinases (RLK), while others have lost their extracellular domains and are found as cytoplasmic kinases. Proteins in this family that are RLKs have a variety of extracellular domains that drive function in a large number of processes, from cell wall interactions to disease resistance to developmental control. This review will briefly cover the major subclasses of RLK/Pelle proteins and their roles. In addition, two specific groups on RLKs will be discussed in detail, relating recent findings in Arabidopsis and how well these conclusions have been able to be translated to agronomically important species. Finally, some details on kinase activity and signal transduction will be addressed, along with the mystery of RLK/Pelle members lacking kinase enzymatic activity.
Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/enzymology , Protein Serine-Threonine Kinases/genetics , Arabidopsis/genetics , Crops, Agricultural/enzymology , Crops, Agricultural/genetics , Multigene Family , Phylogeny , Signal TransductionABSTRACT
Proper control of stem cell populations is key for the development of all multicellular organisms. In Arabidopsis, stem cells are located primarily in the shoot, root and floral meristems where they undergo complex regulation. The Arabidopsis shoot and root meristems are regulated by the related WUS and WOX5 pathways, respectively. Previous studies established that these pathways share the signal transduction components POLTERGEIST (POL) and PLL1. Our latest study in Plant Cell revealed key roles for acyl modifications and lipid binding in the regulation of these two type 2C protein phosphatases. Specifically, POL and PLL1 were shown to localize to the plasma membrane in a myristioylation- and palmitoylation-dependent manner, POL and PLL1 were shown to bind to membrane lipids, and POL activity was found to be stimulated in vitro by the phospholipid PI(4)P. Here, we will discuss what is currently known in Arabidopsis and other organisms about the mechanisms of palmitoylation and provide additional evidence supporting that POL and PLL1 are palmitoylated, including describing the identification of a putative Arabidopsis palmitoyl transferase as a PLL1 interactor.
