All grasses produce spikelets, short branches bearing the florets, which produce the kernels or grain, and therefore much of the calories that feed the world. Maize, and closely related grasses, produce spikelets in pairs, doubling the number of kernels produced in contrast to other, more distantly related cereals, such as rice, wheat and barley, which produce spikelets singly. Understanding the molecular and developmental basis for paired spikelet formation is of great practical significance as this information could be used to double yield in cereals that produce single spikelets. Collaborative comparative genomic studies also provide an unprecedented opportunity to understand the molecular basis for the evolution of this derived trait.

The identification of the suppressor of sessile spikelet (sos) loci in maize provides a breakthrough into the understanding of the formation of the paired spikelet. Molecular, cellular and developmental approaches will be used to dissect the function of Sos1. Additional molecular and developmental studies of Sos2 and Sos3 will enable the identification of additional genes regulating paired spikelet formation. The paired spikelet is produced by a meristem called the spikelet pair meristem. Meristems continually produce organs through balancing the functions of maintenance and determinacy. The Sos loci will enable the dissection of the interaction between these two fundamental developmental processes, as well as providing insight into the evolution of grass inflorescence architecture.

This research involves collaboration between a maize developmental geneticist and an expert in the evolution of grasses, and hence is interdisciplinary in nature. One graduate student and at least six undergraduate students will be trained in the McSteen laboratory. A summer seminar series will be developed to provide training for undergraduates in understanding the broader implications of evolutionary studies in science, education, and society. The PI will also speak to the public on the domestication of corn.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Diane Okamuro
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Donald Danforth Plant Science Center
St. Louis
United States
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