Functional and Evolutionary Analysis of Flowering Time Genes in Brassica nigra and Physcomitrella patens

Hedman, H. 2008. Functional and evolutionary analysis of flowering time genes in Brassica nigra and Physcomitrella patens. Doctor's dissertation. ISSN 1652-6880, ISBN 978-91-85913-88-6. Plant genomes harbour many gene families reminiscent of previous duplication events. In this thesis, the molecular evolution of duplicated genes is analysed with special emphasis on flowering-time genes. In Brassica nigra, a close relative to Arabidopsis , three COL genes have been associated with flowering time (BnCOa, BnCOb and BnCOL1). The molecular evolution of these genes have been studied. All aspects of the data can not easily be explained by demography, indicating that selection has played a role in shaping the variation at these genes. BnCOb appear to be in the early process of pseudogenization. A functional study of COL genes in the moss Physcomitrella patens shows that in Ppcol3 knockout mutants, the generation of gametophores (leafy shoots) was diminished under blue light. Indicating that PpCOL3 is required for gametophore development Stem elongation was affected in white light in Ppcol2-Ppcol3 double mutants, but not in a Ppcol3 single mutant, suggesting that PpCOL2 might be involved in growth regulation of the gametophore. A phylogenetic study of plant PEBP genes show that three major clades exists in land plants: the basal MFT clade and FT and TFL1 clades. An analysis of positively selected sites in the tree branches identified six putatively selected sites. A detailed study of the basal MFT clade, together with an expression analysis in Physcomitrella, shows that moss MFT-like genes are light-induced and appear to be associated with development of reproductive structures.