Floral organogenesis and the developmental basis for pollinator deception in the asiatic dayflower, Commelina communis (Commelinaceae)

Abstract

The upper half of flowers in Commelina communis deceptively lures potential pollinators with its showy petals and staminodes on the false promise of abundant pollen. This paper presents evidence that staminodization in the upper half is associated with a severe retardation of the entire upper floral hemisphere early in development. Possible consequences of this developmental retardation are seen also in the gynoecium, where the upper carpel of the three-carpellate ovary is underdeveloped and sterile at maturity. Only late in development do the upper petals and staminodes expand and acquire pigments necessary for their attractive function. We surmise that retardations of this severity are unlikely to be found for functionally fertile organs such as stamens and ovule-producing carpels, because key preparatory events preceding sporogenesis might otherwise be disrupted. Such differential growth about the floral apex resembles that known in some eudicots to be regulated by the TCP gene family; thus, future molecular developmental studies in Commelina may help to extend our understanding of the evolutionary genetics of floral monosymmetry to monocots.

The Maize PI/GLO Ortholog Zmm16/sterile tassel silky ear1 Interacts with the Zygomorphy and Sex Determination Pathways in Flower Development

“…In particular, the inhibited lodicule shows no evidence of phyllotactic patterning. In many zygomorphic flowers, like those of A. majus, inhibited primordia are initiated but their subsequent growth repressed (Carpenter and Coen, 1990;Rudall and Bateman, 2004;Wang et al, 2008;Hardy et al, 2009). Furthermore, in maize, B class gene expression is asymmetrically absent from the adaxial domain.…”

“…In Antirrhinum majus, and indeed in many zygomorphic flowers, all expected organs initiate, but growth of some is inhibited or altered by the zygomorphy program (Carpenter and Coen, 1990;Rudall and Bateman, 2004;Wang et al, 2008;Hardy et al, 2009). In contrast, there is no morphological evidence for the initiation of the medial-adaxial lodicule in maize.…”

Parallel evolution of TCP and B-class genes in Commelinaceae flower bilateral symmetry

“…In C. communis and C. dianthifolia , each hermaphroditic flower comprises two whorls of three tepals, two whorls of three stamens/staminodes and a whorl of three fused carpels (Figure 2A, B) [54]. In the first whorl of both species, all three outer tepals are membranous, but the lateroventral two are distinct from the dorsal one in both size and shape (Figure 2G).…”

“…In the second whorl of C. dianthifolia all inner tepals are large and showy, but vary slightly in overall size and shape along the dorsoventral axis (Figure 2E, H). By contrast, in the second whorl of C. communis , only the dorsolateral inner tepals are large and showy; the ventral inner tepal is small and membranous, similar to outer tepals (Figure 2D, G) [54]. In the stamen whorls of both species, the dorsal (outer whorl) or dorsolateral (inner whorl) organs are underdeveloped staminodes that function to attract pollinators, but produce few sterile pollen grains (Figure 2D, G, H).…”

“…By contrast, the long lateroventral stamens in the outer whorl, and the medium ventral stamen in the inner whorl are showy and produce viable pollen (Figure 2D, G, H). Finally, in the fifth whorl of both species, the dorsal carpel is underdeveloped and sterile, while the two ventral carpels are fertile [54]. …”