Small RNAs regulating shoot meristem function

A number of key regulatory genes involved in meristem indeterminacy and organ initiation are under the control of small RNAs. To gain insight into the spatial and temporal regulation of such small RNA-controlled gene networks, we are characterizing the precise expression patterns of mature miRNAs by in situ hybridization. In addition, we used laser microdissection to collect cells from distinct functional domains within the shoot apical meristem (SAM) and developing leaf primordia of maize to analyze the expression profiles of small RNA precursors and downstream targets. RNA from twelve distinct regions of the shoot apex were profiled by deep sequencing, and analysis of miRNA precursor and target gene expression revealed that complex regulatory mechanisms underlie the generation of the distinct miRNA expression patterns. In a separate approach, we are taking advantage of mutants defective in miRNA or ta-siRNA biogenesis to identifiy novel small RNAs functioning within the maize shoot apex. Data from analysis of one mutant in the ta-siRNA pathway will be presented.