Grant awarded from The Leverhulme Trust: the innovation of branching in plants

The earliest land floras looked something like the tiny fungi, freshwater algae and lichen crusts that we can see today growing on a roof, tree trunk or wall. Plants originated from algae growing in such crusts around 470 million years ago, and the first land plants resembled modern mosses, each having a tiny simple stem with a swollen reproductive tip. In contrast, the vast majority of today’s land plants are large with elaborate branching shoots that make leaves and flowers from proliferative shoot tips. I am interested in how the switch from simple to elaborate plant forms occurred during evolution and would like to answer questions such as how did branching first arise, how did plants learn to make proliferative shoot tips and how did they later learn to make leaves? These steps were all pivotal in enabling plant life as we know it to conquer the land, and as animals depend on plants for oxygen and food, they ultimately underpinned the radiation of life on Earth.

Over the last decade, newly discovered fossils, genetic techniques and model systems have unlocked the door to answering my fundamental questions about plant evolution. I aim to build on these advances to identify the genes that were responsible for the origin of branching. Most of our knowledge about branching comes from flowering plants, which have a recent evolutionary origin. With my Leverhulme Trust Project Grant I will use a relative of coal swamp plants whose branching form has changed little during the past 300 million years to study the genes involved in branching. This spike moss is called Selaginella kraussiana, and it shows an ancient pattern of branching in which the proliferative shoot tips split in two as the plant grows to give the plant a forking overall structure, rather than the bushy structure of flowering plants. The project will identify any similarities and differences in branching mechanisms between spike mosses and flowering plants and will thereby reveal the route by which branching forms evolved.