Maize Shoot Apical Meristem Architecture: Natural Diversity and Its Genetic Control

The shoot apical meristem (SAM)  is a domed structure containing the stem cells that generate daughter cells that differentiate to become all of the above-ground organs of the plant.  The dual role of organ initiation and stem cell maintenance lead to constraints in SAM size and shape.  The architecture of the SAM is determined in part by the genetic background, and several genes contributing to gross morphology of the SAM have been identified through mutant analyses.  Here, natural variation in SAM architecture was surveyed in a diverse set of maize genotypes and mapped in three related families of recombinant inbred lines.  Six to nine QTL were identified for each of 8 morphological SAM traits.  One QTL for SAM height was validated using three near-isogenic lines.  Expression analysis of shoot apices in one set of RILs was used to correlate gene expression with SAM architecture; together with QTL location information, we identified a list of genes potentially important in shaping the maize SAM.  The contribution and correlation of SAM architecture to adult plant morphology will also be discussed.