A Ds Insertional Mutant of a Barley miR172 Gene Results in Indeterminate Spikelet Development

ABSTRACT A simple, polymerase chain reaction (PCR) and agarose gel‐based system was used to efficiently detect barley ( Hordeum vulgare L.) lines with novel transpositions of a modified maize ( Zea mays L.) Ds element. One line contained a Ds insertion in a gene critical to barley spike development which appears to be a regulatory component of the ABC model of floral development. This model, elucidated based on studies of dicots, is widely conserved and function of key genes–such as AP2 –have been demonstrated in monocots such as rice ( Oryza sativa L.) and maize, but significant differences in orthologous gene function exist. This report describes the generation of a Ds ‐insertional mutant of a putative barley ortholog of miR172 . The miR172 family of microRNAs (miRNAs) includes a member shown to control the expression of AP2 and AP2 ‐like orthologs during floral development. The Ds‐miR172 mutant contains a 3.6 kb insertion in the mature miRNA sequence, thus abolishing function, and the associated floral abnormalities are consistent with the failure to properly regulate the barley AP2 ortholog. Ds‐miR172 mutants show abnormal spikelet development, including the conversion of glumes to partially developed florets in apical regions of spikes. Basal regions of the spike show an abnormal branching phenotype resulting from indeterminate spikelet meristem development, with each branch consisting of multiple, abnormal spikelets and other floral organs in place of a single spikelet. This phenotype is similar to ts4 in maize, the only other known mutation affecting a miR172 ortholog .