Transcriptional gene silencing as a tool for uncovering gene function in maize

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Abstract
Transcriptional gene silencing has broad applications for studying gene function in planta. In maize, a large number of genes have been identified as tassel-preferred in their expression pattern, both by traditional genetic methods and by recent high-throughput expression profiling platforms. Approaches using RNA suppression may provide a rapid alternative means to identify genes directly related to pollen development in maize. The male fertility gene Ms45 and several anther-expressed genes of unknown function were used to evaluate the efficacy of generating male-sterile plants by transcriptional gene silencing. A high frequency of male-sterile plants was obtained by constitutively expressing inverted repeats (IR) of the Ms45 promoter. These sterile plants lacked MS45 mRNA due to transcriptional inactivity of the target promoter. Moreover, fertility was restored to these promoter IR-containing plants by expressing the Ms45 coding region using heterologous promoters. Transcriptional silencing of other anther-expressed genes also significantly affected male fertility phenotypes and led to increased methylation of the target promoter DNA sequences. These studies provide evidence of disruption of gene activity in monocots by RNA interference constructs directed against either native or transformed promoter regions. This approach not only enables the correlation of monocot anther-expressed genes with functions that are important for reproduction in maize, but may also provide a tool for studying gene function and identifying regulatory components unique to transcriptional gene control.