A Ds insertional mutant of a barley miR172 gene results in indeterminate spikelet development

Authors: Brown, Ryan; Bregitzer, Paul

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2011
Publication Date: 1/3/2012
Citation: Brown, R.H., Bregitzer, P.P. 2012. A Ds insertional mutant of a barley miR172 gene results in indeterminate spikelet development. Crop Science. 51:1664-1672.

Interpretive Summary: Developing detailed knowledge of how plants grow and develop is important to scientists seeking to design methods for improving plant characteristics. One important process is flower development, which ultimately is critical to the production of grain for feed and food. This process is relatively well understood in the Arabidopsis plant--which is often used for fundamental research studies because of its simplicity--but is less well-understood in more important crop plants like corn and barley. One useful method for understanding how a gene works is to change its function by generating a mutation in it. This report describes the results of a mutation in the gene miR172 which abolishes its function. The result is the development of repetitive structures--essentially flowers within flowers within flowers. This shows that miR172 is important to the process of switching between the active growth of cells that will become flowers and the process of cells stopping growth and maturing into individual flowers.

Technical Abstract: Descriptions of the genetic control of floral development in higher plants, and the relationships between floral development in dicots and monocots, have been facilitated by studying the effects of mutations in key genes. The ABC model of floral development, elucidated based on studies of dicots, shows widespread conservation among plants. Key features of this model--such as the role and expression of APETELA2 (AP2)-- have been demonstrated in monocots such as rice and maize, but significant differences in orthologous gene function exist. This report describes the generation of a Ds-insertional mutant of a miRNA, miR172, which controls the expression of AP2 orthologs during floral development. The Ds-miR172 mutant contains a 3.6 kb insertion in the mature miRNA sequence, thus aboloshing 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 floral meristem development, with each branch consisting a 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.