CRINKLY4: A TNFR-Like Receptor Kinase Involved in Maize Epidermal Differentiation

Abstract

The maize crinkly4 (cr4) mutation affects leaf epidermis differentiation such that cell size and morphology are altered, and surface functions are compromised, allowing graft-like fusions between organs. In the seed, loss of cr4 inhibits aleurone formation in a pattern that reflects the normal progression of differentiation over the developing endosperm surface. The cr4 gene was isolated by transposon tagging and found to encode a putative receptor kinase. The extracellular domain contains a cysteine-rich region similar to the ligand binding domain in mammalian tumor necrosis factor receptors (TNFRs) and seven copies of a previously unknown 39-amino acid repeat. The results suggest a role for cr4 in a differentiation signal.

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).…”

Cell signaling in root development

“…Recently, a putative transmembrane kinase involved in cell differentiation and a candidate peptide growth factor have been discovered in plants, implying that intercellular signals similar to those employed in animals operate during plant development [3,4]. Nevertheless, surprisingly few studies on signaling pathways involved in plant cell specification exist that combine both genetic and experimental approaches.…”

Between the sheets: inter–cell–layer communication in plant development

“…Mutants in neither gene have phenotypes indicating a role in meristem cell-layer communication, although this could be due to redundancy. CR4-like proteins are characterized by the presence of conserved 39 aa repeats and a TNFR-like repeat in their extracellular domains (Becraft et al 1996). Although no cognate ligands for these proteins have been identified, it seems likely that an apoplastically localized peptide ligand could be involved in the CR4 and ACR4 signalling pathways.…”

“…Mutants in the maize receptor kinase-encoding CRINKLY 4 (CR4) show abnormal epidermal cell behaviour, and in addition show defects in specification of the outer cell layer or aleurone of mutant endosperm (Becraft et al 1996). In maize, many genes expressed in the embryonic protoderm are also expressed in the developing aleurone layer, suggesting that there may be parallels in the mechanisms regulating the development of these two structures (Ingram et al 1999(Ingram et al , 2000Ito et al 2002;Yang et al 2002).…”