Adaptation to life on land: how plants developed UV sunscreens

Abstract

Terrestrial plant life evolved from an aquatic ancestor 400-6-- million years ago. This significant step from water to land involved a suite of genetic adaptations allowing for colonisation of new environments. One such adaptation was for tolerance of incident UV-B radiation. UV-B radiation is particularly damaging to plant life because of its absorption by molecules such as DNA and the production of reactive oxygen species. Therefore the development of UV-B tolerance by early land plants would have been particularly important. Flavonoid synthesis contributes significantly to UV-B tolerance in higher plants, yet it is not known whether the acquisition of flavonoid production allowed the first land plants to tolerate UV-B and colonise the land environment. Here we examine the model bryophyte Marchantia polymorpha, from one of the oldest extant land plant lineages , to determine the effect of flavonoid production in response to UV-B. Under set environmental conditions and UV-B irradiance M. polymorpha is shown to respond to UV-B with an increased production of flavonoid compounds (predominantly flavones). These preliminary results may lead into an understanding of the importance of flavonoid production in enabling the successful colonisation of land by plant life.