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Characterization of the maize pollen transcriptome: Validation of microarray results using quantitative real-time PCR
Citation:
Cooper, L. D., Z. Vejlupkova, A. Qu, L. S. WATRUD, AND J. E. Fowler. Characterization of the maize pollen transcriptome: Validation of microarray results using quantitative real-time PCR. Presented at OSU CGRB Annual Retreat, Redmond, OR, October 04 - 05, 2008.
Impact/Purpose:
Pollen is the primary means of gene flow between plants and plant populations and plays a critical role in seed production.
Description:
Pollen is the primary means of gene flow between plants and plant populations and plays a critical role in seed production. Pollen fitness can be defined as the ability of a particular pollen grain to outcompete other pollen present on the stigma and complete fertilization, thus generating a progeny seed. Current research suggests that many of the mechanisms that influence pollen fitness rely on gene expression in pollen itself. Our overall objective is to better understand the molecular and genetic basis of pollen fitness. As an initial step, we are characterizing the pollen transcriptome of the monocot maize (Zea mays), a model crop plant with easily obtained pollen and a simple assay for testing pollen fitness. A two-color microarray with 57,000 oligonucleotide probes (from the NSF-sponsored Maize Oligonucleotide Array Project – www.maizearray.org) was used to interrogate gene expression levels in maize in seedling, mature pollen and germinated pollen samples from two different inbred lines (B73 and W22). As expected, a large number of probes (~10,000) showed significant expression differences between pollen and seedling, whereas a smaller number of probes (~1000) showed significant differences between the two inbred lines in both pollen and seedling (although these were largely non-overlapping sets). Interestingly, at a stringent statistical cutoff, the microarray data showed no significant differences between mature and germinated pollen. Quantitative RT-PCR experiments are being used to test and validate a subset of the microarray results. Primers were designed to Z. mays PUT (PlantGDB-Assembled Unique Transcript) sequences corresponding to the microarray probes of interest. Preliminary results have validated a number of microarray-detected expression differences, for example, between pollen and seedling samples. In addition, we have found at least two instances of differences in expression between germinated and mature pollen, based on the same microarray data with a less stringent statistical cutoff. Ultimately, we hope to use these data to improve our understanding of pollen fitness and competitive ability and to help identify a set of conserved pollen-enriched genes in maize, rice and Arabidopsis.