The Maize SAM Database is part of a larger collaborative project between the Brent Buckner, Diane Janick-Buckner and Jon Beck labs at Truman State University and Mike Scanlon's lab at Cornell University, Pat Schnable's lab at Iowa State University and Marja Timmerman's lab at Cold Spring Harbor Laboratory. The overall goal of this collaborative project is to identify genes that are required for maize shoot apical meristem (SAM) function and leaf primordia development.

The SAM is a pluripotent mass of cells that is ultimately responsible for the development of all above ground lateral organs (i.e., leaves, flowers and side branches). The SAM exhibits distinct histological regions, marked by tissue zonation and layers. Cells in the periphery of the SAM are recruited to form leaf primordia, while stem cells in the central region of the SAM replace cells in the periphery.

A number of microarray hybridization experiments have been conducted in an effort to identify genes required for meristem function and early stages of leaf development in maize. The Maize SAM Database contains the manual annotations of significantly differentially regulated genes identified in these microarray hybridization studies (Buckner et al., 2007); these annotations are an on-going process. Specifically, these experiments were aimed at identifying genes that are differentially regulated in:

1. The maize SAM compared to the above ground parts of the whole seedling (Ohtsu et al., submitted)
2. The L1 and L2 histological layers of the SAM (Ohtsu et al. in preparation)
3. The SAM of the leaf developmental mutant narrow sheath (Zhang et al., 2007) compared to the non-mutant maize SAM (Scanlon 2000; Nardmann et al., 2004)
4. The SAM of the leaf developmental mutant ragged seedling2 compared to the wild-type maize SAM (Henderson et al., 2005; Henderson et al., 2006)
5. The SAM of the leaf developmental mutant leafbladeless1 compared to wild-type maize SAM (Timmermans et al., 1998)

Buckner, B. Beck, J.,Browning, K.F., Fritz, A.E., Hoxha, E., Grantham, L.D., Kamvar, Z.N., Lough, A.N., Nikolova, O., Schnable, P.S, Scanlon, M.J., and Janick-Buckner, D. Involving Undergraduates in the Annotation and Analysis of Global Gene Expression Studies: Creation of a Maize Shoot Apical Meristem Expression Database. Genetics, in press.

Henderson, D. C., Zhang, X., Brooks, L. and Scanlon, M. J. 2006. RAGGED SEEDLING2 is required for normal expression of KANADI2 and REVOLUTA homologues in the maize shoot apex. Genesis: Journal of Genetics and Development 44: 372-382.

Henderson, D.C., Muehlbauer, G.J., Scanlon, M.J. 2005. Radial leaves of the maize mutant ragged seedling2 retain dorsiventral anatomy. Developmental Biology 282: 455-466.

Nardmann, J. and Ji, J., Werr, W. and Scanlon, M. J. 2004. The maize duplicate genes narrow sheath1 and narrow sheath2 encode a conserved homeobox gene function in a lateral domain of shoot apical meristems. Development 13: 2827-2839.

Ohtsu, K., Smith, M., Emrich, S.J., Borsuk, L.A., Zhou, R., Chen, T., Zhang, X., Timmermans, M.P.C., Beck, J., Buckner, B., Janick-Buckner, D., Nettleton, D.S, Scanlon, M.J. and Schnable, P.S. Expression of retrotransposons in the shoot apical meristem of maize (Zea mays L.). submitted to Plant Journal.

Scanlon, M. J. 2000. NARROW SHEATH1 functions from discrete meristematic foci during recruitment of leaf founder cells in maize. Development 127: 4573-4585.

Timmermans, M.C.P., Schultes, N.P., Jankovsky, J.P. and Nelson, T. 1998. Leafbladeless1 is required for dorsoventrality of lateral organs in maize. Development 125, 2813-2823

Zhang, X., Madi, S.,Borsuk, L., Nettleton, L., Elshire, R.J., Buckner, B., Janick-Buckner, D., Beck, J., Timmermans, M.C.P., Schnable, P.S. and Scanlon, M.J. Laser microdissection of narrow sheath mutant maize uncovers novel gene expression in the shoot apical meristem. Accepted to PLoS Genetics.