1. Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA
2. DuPont Crop Genetics Experimental Station E353, Wilmington, Delaware 19880, USA
3. Department of Biology, University of Missouri–St Louis, St Louis, Missouri 63121, USA
4. †Present address: Department of Biological Sciences, California State University–Long Beach, Long Beach, California 90840, USA

Correspondence to: David Jackson¹ Correspondence and requests for materials should be addressed to D.J. (Email: jacksond@cshl.edu). Accession numbers for gene sequences are listed in Supplementary Fig. 2.

Abstract

Inflorescence branching is a major yield trait in crop plants controlled by the developmental fate of axillary shoot meristems¹. Variations in branching patterns lead to diversity in flower-bearing architectures (inflorescences) and affect crop yield by influencing seed number or harvesting ability^{2, 3}. Several growth regulators such as auxins, cytokinins and carotenoid derivatives regulate branching architectures⁴. Inflorescence branching in maize is regulated by three RAMOSAgenes⁵. Here we show that one of these genes, RAMOSA3 (RA3), encodes a trehalose-6-phosphate phosphatase expressed in discrete domains subtending axillary inflorescence meristems. Genetic and molecular data indicate that RA3 functions through the predicted transcriptional regulator RAMOSA1 (RA1)⁵. We propose that RA3 regulates inflorescence branching by modification of a sugar signal that moves into axillary meristems. Alternatively, the fact that RA3 acts upstream of RA1 supports a hypothesis that RA3 itself may have a transcriptional regulatory function.

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