Developmental and genetic analysis of flowering time in Aquilegia formosa (Ranunculaceae).

摘要

The transition from vegetative to reproductive growth, or flowering, marks an important developmental process in plants. Because the timing of flowering has strong effects on determining which mates will be available for outcrossing, which pollinators will be present to distribute pollen, and the environmental conditions during seed development, dispersal, and germination, flowering time can have major consequences on plant fitness. To maximize reproductive success, plants have evolved genetic mechanisms that allow them to sense their environment and induce flowering under favorable conditions. Substantial gains have been made in understanding the developmental changes and genetic mechanisms controlling flowering time in model species such as the core eudicot Arabidopsis and the monocot grasses rice (Oryza sativa), wheat ( Triticum aestivum), and barley (Hordeum vulgare). In order to gain a better understanding for how flowering time has evolved across diverse taxa, this thesis examines the environmental cues that trigger flowering, the developmental responses that occur in response to these cues, and the genetic pathways that may be controlling these responses in the basal eudicot Aquilegia formosa (Ranunculaceae). This thesis shows that A. formosa has a strong flowering response to vernalization, but shows little response to changing photoperiod. Histological and gene expression studies show that the floral transition occurs in A. formosa by the fourth week of vernalization treatment. Interestingly, expression of AqFT, a homolog to genes known to induce flowering in diverse taxa, is detected at similar levels both prior to and following vernalization, during which the floral transition occurs, indicating that novel mechanisms regulate the floral transition in A. formosa. While specific gene candidates regulating the vernalization response remain elusive in A. formosa, global transcriptome analyses indicate that epigenetic processes related to those regulating vernalization response in Arabidopsis may also regulate vernalization response in A. formosa.