Final Report Summary - EDIP (Evolution of Development In Plants)
Over the last ten years, the fields of developmental genetics and evolution converged to create the discipline of ‘evo/devo’. Work in this exciting area provides insight into how developmental mechanisms evolved to create diverse form and function. In the context of land plant evolution, a few key innovations facilitated the variations in morphology that are seen in extant plant groups. These include the development of multi-cellular embryos, branched shoots, vasculature, leaves, roots, seeds and flowers. Through genetic analyses in model species, a reasonable understanding of how these processes are regulated in flowering plants has been obtained. However, most of the processes evolved before the flowering plants and are thus also features of non-flowering plant species. Understanding developmental pathways in these non-flowering species, has previously been hampered by lack of genome sequence data and by the inability to experimentally manipulate development under laboratory conditions.
In the course of addressing three key biological questions, this project overcame some of the practical limitations of working with non-flowering plant species. Specifically we:
1. Developed new experimental systems for studying algae and hornworts in the lab.
2. Generated substantial genomics resources (both genome and transcriptome) for algae, bryophytes and ferns.
3. Established the first practical transformation method for ferns.
In addition to the technological advances, our work elucidated two fundamental features of land plant evolution. Namely:
1. Single apical initials of the diploid fern sporophyte operate in the same way as those of the haploid moss gametophore, giving rise to single derivatives that form leaves. In contrast, leaves are initiated from two cells in the lycophyte Selaginella kraussiana. These discoveries overturned the idea of a progressive increase in complexity during evolution and instead pointed towards ancestral mechanisms of leaf initiation in bryophytes and monilophytes, and derived mechanisms in lycophytes and seed plants.
2. Polar auxin transport mechanisms are conserved in the lycophyte S. kraussiana and angiosperms, with auxin having a similar role in both lineages in root branching, vascular differentiation and boundary formation in the shoot. However, auxin is not involved in shoot branching or leaf initiation in S. kraussiana, suggesting that independent mechanisms were recruited to regulate phyllotactic patterns in the two lineages and that the role of auxin in angiosperm shoot branching is derived (publication #8).
In the course of addressing three key biological questions, this project overcame some of the practical limitations of working with non-flowering plant species. Specifically we:
1. Developed new experimental systems for studying algae and hornworts in the lab.
2. Generated substantial genomics resources (both genome and transcriptome) for algae, bryophytes and ferns.
3. Established the first practical transformation method for ferns.
In addition to the technological advances, our work elucidated two fundamental features of land plant evolution. Namely:
1. Single apical initials of the diploid fern sporophyte operate in the same way as those of the haploid moss gametophore, giving rise to single derivatives that form leaves. In contrast, leaves are initiated from two cells in the lycophyte Selaginella kraussiana. These discoveries overturned the idea of a progressive increase in complexity during evolution and instead pointed towards ancestral mechanisms of leaf initiation in bryophytes and monilophytes, and derived mechanisms in lycophytes and seed plants.
2. Polar auxin transport mechanisms are conserved in the lycophyte S. kraussiana and angiosperms, with auxin having a similar role in both lineages in root branching, vascular differentiation and boundary formation in the shoot. However, auxin is not involved in shoot branching or leaf initiation in S. kraussiana, suggesting that independent mechanisms were recruited to regulate phyllotactic patterns in the two lineages and that the role of auxin in angiosperm shoot branching is derived (publication #8).