Developmental Regulation of Cell Interactions in theArabidopsis fiddlehead-1Mutant: A Role for the Epidermal Cell Wall and Cuticle

Abstract

Although the plant epidermis serves primarily a protective role, during plant development some epidermal cells specialize, becoming competent to interact not only with pollen but also with other epidermal cells. In the former case, these interactions mediate recognition, germination, and pollen growth responses and, in the latter case, result in interorgan fusions which, most commonly, alter floral architecture in ways that are thought to promote reproductive success. In either case, all of the initial signaling events must take place across the cell wall and cuticle. In Arabidopsis, mutation of the FIDDLEHEAD gene alters the shoot epidermis such that all epidermal cells become competent to participate in both types of interactions. In fdh-1 mutants, epidermal cells manifest not only a contact-mediated fusion response but also interact with pollen. Since carpel epidermal derivatives manifest both of these properties, we postulated that fdh-1 epidermal cells were ectopically expressing a carpel-like program. In this report we demonstrate that manifestation of the fdh-1 phenotype does not require the product of the AGAMOUS gene, indicating that the phenotype is either independent of the carpel development program or that fdh-1 mutations activate a carpel-specific developmental program downstream of the AG gene. Furthermore, we demonstrate that plants bearing mutations in the fdh-1 gene show significant changes in cell wall and cuticular permeability. Biochemical analyses of the lipid composition of the crude cell wall fraction reveal that fdh-1 cell walls differ from wild-type and manifest significant changes in high-molecular-weight lipid peaks. These results suggest that cell wall and cuticular permeability may be important determinants in developmental signaling between interacting cells and implicate lipids as important factors in modulating the selectivity of the permeability barrier presented by the epidermal cell wall and cuticle.

Adaptive sequence evolution is driven by biotic stress in a pair of orchid species (Dactylorhiza) with distinct ecological optima

“…This is part of the DIHYDROKAEMPFEROL 4‐REDUCTASE activity with a role in flavonoid biosynthesis, again potentially linked to plant defence. Finally, a homolog of 3‐KETOACYL‐SYNTHASE 10 , with a role in developing cuticular wax, is also evidenced as a target of positive selection on the D. fuchsii branch, potentially in response to viral pressure (Lolle et al., 1997). …”

The Effects of Polyethylene Glycol on Gene Expression of Developing White Spruce Somatic Embryos

“…In angiosperms, some of the molecular components required for the formation and maintenance of the SAM have been identified, and they require a complex network of interactions among genes, including ZLL (ZWILLE), AGO (ARGONAUTE), ERECTA, NAM (NO APICAL MERISTEM), CLV1 (CLAVATA 1), and FIDDLEHEAD (Clark et al, 1996;Souer et al, 1996;Lolle et al, 1997;Bohmert at al., 1998;Moussian et al, 1998;Yokoyama et al, 1998). The existence of several pine cDNAs, apparent homologs to these genes, suggests that similar mechanisms govern SAM activity in angiosperms and gymnosperms.…”

Functional conservation and maintenance of expression pattern of FIDDLEHEAD-like genes in Arabidopsis and Antirrhinum

“…The epidermis-specific FDH gene is implicated in the control of a barrier function associated with the outermost cell walls of the epidermis (Lolle et al, 1997;Yephremov et al, 1999;Pruitt et al, 2000). Suppression of this function in fdh mutants results in ectopic organ fusions, and allows wildtype pollen to germinate on the leaf epidermis of fdh mutants (Lolle et al, 1992;Lolle and Cheung, 1993).…”