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.
Highlights
Flowering plants bear beautiful flowers to attract pollinators
Suppression of AGAMOUS activity in the perianth whorls is important for petal growth, and this process is controlled by AP2, AINTEGUMENTA, LEUNIG, SEUSS, RABBIT EARS, ROXY1, and STERILE APETALA (Liu and Meyerowitz, 1995; Byzova et al, 1999; Conner and Liu, 2000; Krizek et al, 2000, 2006; Franks et al, 2002; Sridhar et al, 2004; Xing et al, 2005; Grigorova et al, 2011)
We examined the phenotype of two transfer DNA (T-DNA) insertion mutants for the FOP1 gene after gene identification (Supplemental Fig. S3, see below) and found that they showed a similar phenotype to fop1-1 (Fig. 1, C and D)
Summary
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. 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 petals (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. 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. Characterization and expression analysis of FOP1 suggests that FOP1 products, synthesized in the petal epidermis, play a lubricant role during petal elongation
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