Underlying mechanisms of development: pollen wall ontogeny inChloranthus japonicusand a reconsideration of pollen ontogeny in early-diverging lineages of angiosperms

Abstract

Despite the large amount of knowledge accumulated, a precise understanding of the morphogenesis of the intricate and complex pollen walls (exines) is incomplete. A new factor (simple physico-chemical interactions) is shown to be involved in exine development. The stages of exine development in many species show remarkable similarity with successive micellar self-assembling mesophases of a colloidal system. Currently, > 100 genes have been reported to play a role in exine deposition, but nothing contradicts the view that specific patterns of exines are based on physico-chemical principles of space-filling operations taking place after genomic control of the concentrations of the source materials. On the examples of Chloranthus japonicus, magnoliids and other early-diverging angiosperms we show that exine development unfolds by two physico-chemical processes (phase separation and self-assembly) after genomic control, revealing an interplay between genomic and physical processes.