Roles of meiotic-stage non-coding RNAs in maize anther development

Pollen production and regulation of plant fertility are essential to agriculture. Hybrid corn and other grains have significantly boosted world food production. This project will investigate the functions of RNAs that support pollen development in anthers (the organs that make pollen in flowering plants). The project will utilize plant genomics and developmental biology to determine the biological roles of small RNAs and the proteins that utilize them for anther functions. These RNAs are required for robust male fertility: in the absence of the small RNAs, at normal temperatures, development fails, yielding male sterility. Fertility can be rescued under lower temperatures, linking environmental conditions to the role of these small RNAs. The project focuses on maize because it is an optimal system for the proposed experiments; plus, male fertility is key to the production of hybrid corn seed. Outcomes of this project could include improved control of male fertility in grass crops. Broader impacts of the project include training of students in plant and RNA biology. The project will focus specifically on the class of 24-nt phased, secondary siRNAs, known as “24-nt phasiRNAs” that are highly enriched in meiotic-stage anthers. The project will characterize phenotypes and molecular genetic analysis of loss-of-function knock-outs including the Dicer-like5 (Dcl5) gene, for which the preliminary data demonstrate male sterility. The questions to be addressed by this project include which basic Helix-Loop-Helix transcription factors function to activate transcription of the 24-nt phasiRNAs? How does the core biogenesis protein DCL5 function, and what is the exact nature of the phenotype of sterility in its absence? Are there genetic modifiers of the dcl5 conditional phenotype in other backgrounds of maize? What are the key catalytic Argonaute proteins that load the 24-nt phasiRNAs for their function? And what are the target RNAs with which the phasiRNA-loaded Argonaute proteins interact? This award was co-funded by the Genetic Mechanisms Cluster in the Division of Molecular and Cellular Biosciences and the Plant Genome Research Program in the Division of Integrative Organismal Systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.