Molecular analysis of the CRINKLY4 gene family in Arabidopsis thaliana

Abstract

The maize (Zea mays L.) CRINKLY4 (CR4) gene encodes a serine/threonine receptor-like kinase that controls an array of developmental processes in the plant and endosperm. The Arabidopsis thaliana (L.) Heynh. genome encodes an ortholog of CR4, ACR4, and four CRINKLY4-RELATED (CRR) proteins: AtCRR1, AtCRR2, AtCRR3 and AtCRK1. The available genome sequence of rice (Oryza sativa L.) encodes a CR4 ortholog, OsCR4, and four CRR proteins: OsCRR1, OsCRR2, OsCRR3 and OsCRR4, not necessarily orthologous to the Arabidopsis CRRs. A phylogenetic study showed that AtCRR1 and AtCRR2 form a clade closest to the CR4 group while all the other CRRs form a separate cluster. The five Arabidopsis genes are differentially expressed in various tissues. A construct formed by fusion of the ACR4 promoter and the GUS reporter, ACR4::GUS, is expressed primarily in developing tissues of the shoot. The ACR4 cytoplasmic domain functions in vitro as a serine/threonine kinase, while the AtCRR1 and AtCRR2 kinases are not active. The ability of ACR4 to phosphorylate AtCRR2 suggests that they might function in the same signal transduction pathway. T-DNA insertions were obtained in ACR4, AtCRR1, AtCRR2, AtCRR3 and AtCRK1. Mutations in acr4 show a phenotype restricted to the integuments and seed coat, suggesting that Arabidopsis might contain a redundant function that is lacking in maize. The lack of obvious mutant phenotypes in the crr mutants indicates they are not required for the hypothetical redundant function.

ARABIDOPSIS CRINKLY4 Function, Internalization, and Turnover Are Dependent on the Extracellular Crinkly Repeat Domain

“…As previously reported, it is predicted to fold into a b-propeller type structure (McCarty and Chory, 2000;Cao et al, 2005). A core C(X;10)CWG sequence motif is highly conserved amongst the repeats.…”

“…The two major domains within the extracellular region of ACR4 are a domain consisting of seven repeats termed ''crinkly repeats'' (Cao et al, 2005) and a domain with homology to the three Cysrich repeats of the tumor necrosis factor receptor (TNFR) extracellular domain. In construct DREPEAT, 4.5 of the 7 crinkly repeats had been deleted, and in construct DTNFR, the entire TNFR homology domain was removed.…”

“…One explanation for this observation could lie in the possibility that ACR4 may oligomerize with another kinase-active receptor kinase or be phosphorylated by a cytoplasmic kinase. Interesting new work has indeed shown that the ACR4 kinase domain is capable of phosphorylating the kinase domain of AtCRR2, one of four Arabidopsis RLKs closely related to ACR4, in vitro (Cao et al, 2005). AtCRR2 is kinase dead because of the deletion of a critical section of its kinase domain.…”

Arabidopsishomeodomain-leucine zipper IV proteins promote stomatal development and ectopically induce stomata beyond the epidermis

“…The HDG2 promoter also possesses L1 box (Nakamura et al, 2006), and its auto-activation may contribute to robust progression of stomatal development. Specification of the protoderm (L1 layer) in Arabidopsis involves cell-cell signaling mediated by receptor-like kinases ARABIDOPSIS CRINKLY4 (ACR4) and ABNORMAL LEAF SHAPE2 (ALE2), a putative cysteine peptidase DEFECTIVE KERNEL1 (AtDEK1) and a putative subtilase ALE1 (Becraft et al, 1996;Cao et al, 2005;Johnson et al, 2005;Tanaka et al, 2001;Tanaka et al, 2007). The signaling pathways appear to act upstream of AtML1 and PDF2, which in turn may promote expression of AtDEK1 and ALE2 as part of a positive-feedback loop (Javelle et al, 2011b).…”

Subcellular Localization and Functional Domain Studies of DEFECTIVE KERNEL1 in Maize andArabidopsisSuggest a Model for Aleurone Cell Fate Specification Involving CRINKLY4 and SUPERNUMERARY ALEURONE LAYER1

“…In maize, Cr4 is also required for normal leaf epidermis development (Becraft et al, 2001). Mutations in Arabidopsis CRINKLY4 (ACR4) demonstrate a role for this protein in the regulation of cellular organization during the development of leaves, sepal margins, ovule integuments, and the endothelium (Tanaka et al, 2002;Watanabe et al, 2004;Cao et al, 2005). One study using green fluorescent protein (GFP)-tagged ACR4 localized the green fluorescent signal preferentially on the lateral and basal plasma membrane domains in the epidermis of the leaf primordia (Tanaka et al, 2002).…”