The Role of microRNA172 in Regulating the Barley Cleistogamy 1 Gene

Floret gaping in a non-cleistogamous barley is promoted by the swelling of the lodicule. Cleistogamy in barley is under the control of Cleistogamy 1 (cly1), a gene which has proven to be a member of the APETALA2 transcription factor family. A sequence polymorphism at an miR172 target site within cly1 is associated with lodicule development and hence with the cleistogamy phenotype. Our working hypothesis is that miR172 activity reduces the abundance of AP2 protein. An analysis of sRNA sequence reveals that the immature barley spike transcriptome includes a population of miR172 molecules. In situ hybridization experiments show that miR172 and cly1 mRNA co-localize in the lodicule primordium. The expression profile of the identified miR172s showed that, and these observations are supported by qPCR analysis. Among the three known barley miR172 genes, only the product of miR172a is abundant in the immature spike. We demonstrate some direct evidence to show that the interaction between cly1 mRNA and miR172a is an important component of the mechanism underlying lodicule development. Experiments are in progress to determine whether cly1 down-regulation is achieved by either miR172 cleavage of cly1 mRNA or by the repression of its translation. The implication is that non-cleistogamy is regulated by the interaction of miR172 with AP2 orthologs in other cereals, such as TaAP2 in wheat and SHAT1 in rice.