Physical Interaction of Floral Organs Controls Petal Morphogenesis in Arabidopsis    

Abstract

Flowering plants bear beautiful flowers to attract pollinators. Petals are the most variable organs in flowering plants, with their color, fragrance, and shape. In Arabidopsis (Arabidopsis thaliana), petal primordia arise at a similar time to stamen primordia and elongate at later stages through the narrow space between anthers and sepals. Although many of the genes involved in regulating petal identity and primordia growth are known, the molecular mechanism for the later elongation process remains unknown. We found a mutant, folded petals1 (fop1), in which normal petal development is inhibited during their growth through the narrow space between sepals and anthers, resulting in formation of folded petals at maturation. During elongation, the fop1 petals contact the sepal surface at several sites. The conical-shaped petal epidermal cells are flattened in the fop1 mutant, as if they had been pressed from the top. Surgical or genetic removal of sepals in young buds restores the regular growth of petals, suggesting that narrow space within a bud is the cause of petal folding in the fop1 mutant. FOP1 encodes a member of the bifunctional wax ester synthase/diacylglycerol acyltransferase family, WSD11, which is expressed in elongating petals and localized to the plasma membrane. These results suggest that the FOP1/WSD11 products synthesized in the petal epidermis may act as a lubricant, enabling uninhibited growth of the petals as they extend between the sepals and the anthers.

Comprehensive characterization of a floral mutant reveals the mechanism of hooked petal morphogenesis in Chrysanthemum morifolium

“…Rudimentary hooked petals did not become visible until the SEB stage (Figure ). The implication is that the phenotype is not generated until the later stage of floral development, at a time when cell expansion predominates over cell division (Hill and Lord, ; Takeda et al ., ; Yamada et al ., ). Consistently, cell size in the ‘ADG’ petals was smaller than in those of ‘MADG’ (Figure g–j), indicating the defects in cell expansion.…”

Perspectives on MADS-box expression during orchid flower evolution and development

“…For example, because most studies describe orchid flowers buds based on their size it is not possible to make an objective comparison of transcriptomes or other patterns of gene expression within and between species. An alternative would be that for every species with a transcriptome a description of discrete stages of its development is generated and considered in the design of future expression studies as it is routinely done for Arabidopsis thaliana (Smyth et al, 1990; Niederhuth et al, 2013; Takeda et al, 2013). …”

Surface wax esters contribute to drought tolerance in Arabidopsis

“…WSD11, another member of the Arabidopsis WSD family, is required for normal petal growth. Petals in the wsd11 mutant (synonymous: fop1 , folded petal 1), are folded during growth in flower buds (Takeda et al ., ). Euglena gracilis produces wax esters as an alternative storage compound during anaerobic conditions, when a certain proportion of reducing equivalents is re‐oxidized during the reduction of fatty acids to alcohols (wax ester fermentation).…”