Meristem Maturation and Flower Production in the Solanaceae

Evolution of phenotypic diversity is founded on variation in the regulatory networks that guide developmental processes. One of the most remarkable manifestations of such variation is found among inflorescences. In the Solanaceae family, inflorescences range from solitary flowers to highly branched structures that produce hundreds of flowers. We are taking advantage of the many virtues of tomato and related Solanaceae to address whether variation in inflorescence complexity is based on differences in the maturation of meristems from vegetative to reproductive states. We are profiling transcriptomes from ontogenetically matched meristem stages from five Solanaceae representing a complete range of inflorescence complexity. Using clustering algorithms and other tools to compare transcriptome dynamics, we have found that early (vegetative) and late (floral) stages of meristem maturation are much more similar between species compared to the transition stage – the stage preceding morphological changes marking initiation of reproductive growth. Based on these findings, we have formulated a “bubble” model for meristem maturation, in which hidden behind nearly indistinguishable meristem ontogenies is an underlying “molecular maturation clock”. We will discuss evidence suggesting that, depending on the species, the maturation clock either speeds up or slows down at the transition stage to determine whether an inflorescence will be single-flowered, highly branched, or somewhere in between. We are mining our transcriptome data to identify and characterize genes that function within the bubble, and thus could be used to manipulate branching and flower production in crops.