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Pollen tube germination in maize does not require transcriptomic changes
Citation:
Cooper, L. D., Z. Vejlupkova, J. Elser, P. Dharmawardhama, P. Jaiswal, L. S. WATRUD, AND J. E. Fowler. Pollen tube germination in maize does not require transcriptomic changes. Presented at Maize Genetics Meeeting, St. Charles, IL, March 17 - 20, 2011.
Impact/Purpose:
One objective for our group is to better understand the molecular and genetic basis of pollen and pollen tube function, given its critical role in seed production and its importance as a means of gene flow between plant populations.
Description:
One objective for our group is to better understand the molecular and genetic basis of pollen and pollen tube function, given its critical role in seed production and its importance as a means of gene flow between plant populations. We compared gene expression levels in seedlings, mature pollen and in vitro-germinated pollen from two different inbred lines (B73 and W22) using the Arizona microarray (maizearray.org). As expected, a large number of probes (>10,000) showed significant expression differences between pollen and seedling. In addition, a substantial number of probes (~1000) detected significant differences between the two inbred lines in either seedling or pollen. In contrast, no probes detected significant quantitative differences between RNA species in mature and germinated pollen. Furthermore, based on Gene Ontology term enrichment analysis, transcripts in mature pollen are enriched in several categories associated with active metabolism. This contrasts with the transcriptome of mature pollen in Arabidopsis, which is not enriched in metabolic processes, and shows significant transcriptomic change upon germination of the pollen tube (Wang et al. 2008). This suggests that, in contrast to Arabidopsis, mature pollen in maize, which remains ‘partially hydrated’ at anthesis, is metabolically active and does not rely upon novel transcription patterns for germination. Experiments using the transcriptional inhibitor actinomycin D support this hypothesis, as maize pollen germination is relatively insensitive to the drug. Furthermore, comparative genomics shows a significant overlap in orthologous genes when comparing the transcripts of mature pollen in maize with post-germination pollen in Arabidopsis. We are using some of the new sequence-indexed mutant resources in maize to test whether this set of orthologous genes is associated with important functions in male gametophyte development.