Assistant Professor University of Florida Gainesville, Florida
Body of Abstract: Maize (Zea mays L.) is a monoecious plant with unisexual female and male flowers. The male inflorescence, identified as tassel, is positioned in the apex of the plant. In maize, floral meristems are developed from spikelet meristems after a series of auxiliary meristem branching events. Using a transcriptional profiling during meristem development, we identified ZmMADS1 as a gene with a strong induction prior to the shoot apical meristem transition from vegetative to reproductive growth in maize. To examine whether ZmMADS1 is indeed involved in regulating meristem transition and development, we generated overexpression and RNA interference (RNAi) maize lines under the control of the maize UBI promoter. Overexpression of ZmMADS1 resulted in reduced number of tassel branches but larger compared to wild-type plants. In contrast, ZmMADS1-RNAi plants showed similar number of tassel branches as wild-type, but significatively smaller. We did not observe any differences in ear size and kernel number. We used scanning electron microscopy to compare the developmental progression of inflorescence primordia from ZmMADS1 overexpressor, RNAi and wild type plants. The transition from vegetative to reproductive meristem was significantly shorter in overexpressor plants compared to wild-type and RNAi plants which might have contributed to the reduced number of branches in the overexpression plants. To determine the molecular mechanisms underlying the branching/size tassel phenotype, we used RNA-seq to profile gene expression in overexpressors, RNAi and wild-type plants during tassel development. We found genes and pathways associated with flowering time and transition to reproductive growth since overexpression and RNAi plants have different flowering times compared to wild-type. To further understand the role ZmMADS1 during tassel development, we conducted a cluster correlation analysis using the “cor” function implemented in the R package WGCNA and identified groups of genes involved in controlling tassel development in maize.