The role of auxin during reproductive organ development in the flowering plant model species Arabidopsis thaliana and for differentiation and polarity establishment in the moss Physcomitrella patens
Auxin in Arabidopsis gynoecia and stamen development
Several key genetic regulators of gynoecium development relate to the synthesis, transport or signal transduction of the plant hormone auxin. We are therefore studying auxin dynamics during the earliest stages of gynoecium primordial development, when tissue domains are specified. Transient disruption of polar auxin transport (PAT) results in ectopic auxin responses, broadened expression domains of medial tissue markers, and disturbed lateral preprocambium initiation. We suggest that gynoecial valve outgrowth depends on PIN1-mediated lateral auxin maxima as well as subsequent internal auxin drainage and provascular formation. In addition, PAT is required to prevent the lateral domains, at least in the apical portion of the gynoecial primordium, from obtaining medial fates. We are also studying the importance of auxin during stamen development.
Auxin dynamics are strongly regulated and important for differentiation and growth during moss development
Most available data suggest that the evolution of the diploid multi-cellular sporophyte dominating the higher plant life cycle involved the recruitment of existing gametophytic developmental programs of the haploid early bryophytes (Floyd and Bowman 2007). We have studied the role of the plant hormone auxin in the haploid gamtetophyte of moss, by modulating the expression levels of moss homologues of the STY/SHI auxin biosynthesis regulators, of auxin biosynthesis genes, as well as of genes encoding homologues of PIN and LAX auxin transporters. Overexpression, knock-out and reporter gene knock-in in these genes verify their conserved roles and reveal that auxin biosynthesis together with auxin transport regulates auxin peak formation in the moss gametophore. These are important for cell differentiation and growth of protonemal tissue, as well as of leaves and reproductive organs. We are currently studying the role of auxin in the regulation of PCD during moss reproductive organ development.