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Global gene expression in the maize shoot apical meristem

ABSTRACT: All above ground organs of higher plants are ultimately derived from specialized organogenic structures called shoot apical meristems (SAMs). It is comprised of pluripotent stem cells, which divide to regenerate themselves as well as to provide cells to form other organs such as leaves and stems. To study global gene expression in maize SAM and very young primordia (P0 and P1), RNA was extracted from both whole SAMs (SAMs, P0 and P1) and whole seedlings (above ground part of seedlings) collected from 14-day old B73 seedlings. These RNA samples were labeled and hybridized with cDNA microarrays that have about 30,000 maize cDNA clones. Statistical analyses showed that approximately 7% and 8% of the tested genes were significantly up-regulated and down-regulated, respectively. Several control genes, whose expressions were confirmed in the maize SAM in the previous studies, were significantly up-regulated. Many histone genes and cell cycle related genes were also significantly up-regulated. Those observations validated our microarray results. The significantly up-regulated genes involved many novel transcription factor genes and regulatory genes as well as some kind of enzymes, suggesting those genes play important roles in meristem maintenance and the early stage of leaf development in maize. Surprisingly, several retrotransposon-related genes were greatly up-regulated with the statistical significance. This finding raised the possibility that retrotransposons are involved in regulatory mechanism of maize SAM. Keywords: cell type comparison design

ORGANISM(S): Zea mays

PROVIDER: GSE4004 | GEO | 2007/11/13

SECONDARY ACCESSION(S): PRJNA95221

REPOSITORIES: GEO

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Project description:All above ground organs of higher plants are ultimately derived from specialized organogenic structures termed shoot apical meristems (SAMs). The SAM exhibits distinctive structural organization, marked by cell layering. Maize SAMs are comprised of two cell layers, L1 (single cell layered tunica) and L2 (corpus). To identify genes required for layer-specific functions intact maize SAMs were fixed, embedded in paraffin and sectioned. L1 and L2 cells were isolated from these sections via laser capture microdissection (LCM). RNA was isolated from six biological replications of L1 and L2, amplified and hybridized to microarrays spotted with ~37,000 maize cDNA clones. This experiment identified ~700 ESTs that are preferentially expressed in the L1 or the L2 (P <0.001). The L1-up-regulated ESTs included ZmOCL1 and ZmOCL4, which are known to exhibit L1-specific expression in the maize SAM. The L2-up-regulated ESTs included KNOTTED1, whose transcripts are known to accumulate in the L2 but not in the L1 of the maize SAM. Differentially expressed ESTs included genes involved in transcription, signal transduction, transport and metabolism, many of which are novel candidates that are required for layer-specific functions in the maize SAM. Several L1-up-regulated ESTs were annotated as yabby family genes or basic helix-loop-helix transcription factor-like genes, which have not previously been reported as having layer-specific expression in the SAM. Novel WW domain-containing genes (WW genes) were identified in this study. The WW domain mediates protein-protein interactions, often with signal transduction components. These WW genes were substantially up-regulated in the L1 relative to the L2. Keywords: Cell Type Comparison An experimental aim is to identify genes that are differentially expressed in distinct histological cell layers of maize SAM by comparing the transcript accumulation between L1 (single cell layered tunica) and L2 (corpus) using cDNA microarrays that have over 37,000 informative spots from maize.

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Global gene expression in the maize shoot apical meristem

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