ARS | Publication request: Microdissection of Shoot Meristem Functional Domains

Submitted to: PLoS Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 9, 2009
Publication Date: May 5, 2009
Citation: Brook, Iii, L., Strable, J., Ware, D., Nettleton, D., Scanlon, M.J. 2009. Microdissection of Shoot Meristem Functional Domains. PLoS Genetics. 5(5): e1000476. DOI: 10.1371/journal.pgen.1000476.

Interpretive Summary: In plants the meristems maintain the pool of cells with no fixed identity. From this pool come the cells which will develop into the specific part of the plants, such as the leaves, root and flowers. The shoot apical meristem can be divided into several different parts, where previous work has demonstrated that specific tissues will develop from. Using a laser, the meristem was dissected into discrete regions and the RNA was extracted and used to identify the genes from each section. Comparison of the genes in each region showed some interesting differences in the function of the differentially expressed genes. One region showed an increase in expression of genes involved in cell division and modification of the genomic DNA. Another region showed a down regulation in genes known to be associated with hormones that regulate growth. A set of the genes were experimentally confirmed using a techniques that allows the visualization of expression patterns in the context of the plant organ.

Technical Abstract: The shoot apical meristem (SAM) maintains a pool of indeterminate cells within the SAM proper, while lateral organs are initiated from the SAM periphery. Laser microdissection–microarray technology was used to compare transcriptional profiles within these SAM domains to identify novel maize genes that function during leaf development. Nine hundred and sixty-two differentially expressed maize genes were detected; control genes known to be upregulated in the initiating leaf (P0/P1) or in the SAM proper verified the precision of the microdissections. Genes involved in cell division/growth, cell wall biosynthesis, chromatin remodeling, RNA binding, and translation are especially upregulated in initiating leaves, whereas genes functioning during protein fate and DNA repair are more abundant in the SAM proper. In situ hybridization analyses confirmed the expression patterns of six previously uncharacterized maize genes upregulated in the P0/P1. P0/P1-upregulated genes that were also shown to be downregulated in leaf-arrested shoots treated with an auxin transport inhibitor are especially implicated to function during early events in maize leaf initiation. Reverse genetic analyses of asceapen1 (asc1), a maize D4-cyclin gene upregulated in the P0/P1, revealed novel leaf phenotypes, less genetic redundancy, and expanded D4-CYCLIN function during maize shoot development as compared to Arabidopsis. These analyses generated a unique SAM domain-specific database that provides new insight into SAM function and a useful platform for reverse genetic analyses of shoot development in maize.