STRELIN Marina Micaela
Delayed differentiation of epidermal cells walls can underlie pedomorphosis in plants: the case of pedomorphic petals in the hummingbird-pollinated Caiophora hibiscifolia (Loasaceae, subfam. Loasoideae) species
STRELIN MARINA; ZATTARA EDUARDO; KRISTIAN ULLRICH; SCHALLENBERG-RÜDINGER MAREIKE; RENSING STREFAN
BioMed Central Ltd.
Background: Understanding the relationship between macroevolutionary diversity and the origin of variation in organism development is one of the main goals of evolutionary biology. Variation in the morphology of several plant and animal lineages is attributed to pedomorphosis, a case of heterochrony where an ancestral juvenile shape is retained in an adult descendant. Pedomorphosis facilitated morphological adaptation in an array of plant lineages, but its cellular and molecular basis needs further exploration. Plant development differs qualitatively from animal development in that cells are enclosed by cell walls and do not migrate. Moreover, in many plant lineages, the differentiated epidermis of leaves, and leaf-derived structures like petals, limits organ growth. We therefore proposed that pedomorphosis in leaves, and in leaf-derived structures, results from delayed differentiation of epidermal cells with respect to reproductive maturity. This idea was explored for petal evolution, given the importance of corolla morphology for angiosperm reproductive success. Results: By comparing cell morphology and transcriptional profiles between 5 mm flower buds and mature flowers of an early diverged and a late diverged Loasoideae species (a lineage that experienced transitions from bee- to hummingbird-pollination), we show that evolution of pedomorphic petals of an ornithophile species likely involved delayed differentiation of epidermal cells with respect to flower maturity. We also found that developmental mechanisms other than pedomorphosis might have contributed to evolution of corolla morphology. Conclusions: Our results highlight a need for sometimes moving away from a flower-centric perspective when studying the origin of variation in flower morphology, as this variation can be generated by developmental processes that are also shared with leaves.