Submitted to: Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/10/2008
Publication Date: 1/9/2009
Citation: Acosta, I.F., Laparra, H., Romero, S.P., Schmelz, E.A., Hamberg, M., Mottinger, J.P., Moreno, M.A., Dellaporta, S.L. 2009. tasselseed1 is a lipoxygenase affecting jasmonic acid signaling in sex determination of maize. Science. 323:262-265. Interpretive Summary: The control of pollen and pistil development in maize floral meristems has significant influence on plant architecture and ultimately seed production. Despite the potential for practical applications in agriculture, numerous genes controlling sex determination in maize floral meristems remain unknown. In collaboration with researchers at Yale University (Department of Molecular, Cellular and Developmental Biology) scientists at the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, have discovered that the gene tasselseed1 (ts1) encodes a predicted lipoxygenase that regulates programmed cell death and abortion of developing pistils to produce unisexual tassels, technically known as staminate florets. Normally localized to maize ears, double mutants of ts1 display altered reproductive architecture and production of seeds within the tassels. Consistent with predicted ability to promote synthesis of the plant hormone jasmonic acid, double mutant ts1 plants displayed a 10-fold decrease in jasmonic acid production and lipid peroxidation activity. Physical applications of jasmonic acid to the developing meristems of double mutant ts1 plants recovered the formation of wild-type tassels. While jasmonic acid is most closely associated with wound and defense signaling in plants, we demonstrate that jasmonic acid also has important roles in the sex determination processes of maize.
Technical Abstract: Sex determination in maize is controlled by a developmental cascade leading to the formation of unisexual florets derived from an initially bisexual floral meristem. Abortion of pistil primordia in staminate florets is controlled by a tasselseed-mediated cell death process. Here, we describe the positional cloning and functional characterization of the sex determination gene tasselseed1 (ts1). The TS1 protein encodes a plastid-targeted lipoxygenase with predicted 13-LOX regiospecificity, suggesting that TS1 may be involved in the biosynthesis of the plant hormone jasmonic acid (JA). In the absence of a functional ts1 gene, lipoxygenase activity was absent and endogenous JA levels were greatly reduced in developing inflorescences as compared to wild-type. Exogenous application of JA to developing inflorescences rescued the wild type phenotype in mutant ts1 spikelets. Our findings reveal an unexpected role for jasmonic acid in the determination of staminate spikelets, a sex determination process that involves the abortion of pistil primordia.