Zea mays Transcriptome or Gene expression. Zea mays

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 Overall design: An experimental aim is to identify genes preferentially expressed in maize SAM by comparing the transcript abundant between whole SAMs and whole seedlings using cDNA microarrays that have about 30,000 maize cDNA clones.