Molecular Plant Advance Access originally published online on July 21, 2008
Molecular Plant 2008 1(5):751-759; doi:10.1093/mp/ssn036
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Transcriptome-Based Examination of Putative Pollen Allergens of Rice (Oryza sativa ssp. japonica)
a Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA
b Plant Molecular Biology and Biotechnology Laboratory, Australian Research Council Centre of Excellence for Integrative Legume Research, Faculty of Land and Food Resources, The University of Melbourne, Parkville, Vic. 3010, Australia
1 To whom correspondence should be addressed. E-mail srussell{at}ou.edu, fax +1-405-325-7619, tel. +1-405-325-7619.
Pollen allergens are among the most abundantly transcribed and translated products in the life history of plants, and particularly grasses. To identify different pollen allergens in rice, putative allergens were identified in the rice genome and their expression characterized using the Affymetrix 57K rice GeneChip microarray. Among the most abundant pollen-specific candidate transcripts were Ory s 1 beta-expansin, Ory s 2, Ory s 7 EF hand, Ory s 11, Ory s 12 profilin A, Ory s 23, glycosyl hydrolase family 28 (polygalacturonase), and FAD binding proteins. Highly expressed pollen proteins are frequently present in multiple copy numbers, sometimes with mirror images located on nearby regions of the opposite DNA strand. Many of these are intronless and inserted as copies that retain nearly exact copies of their regulatory elements. Ory s 23 reflects low variability and high copy number, suggesting recent gene amplification. Some copies contain pseudogenes, which may reflect their origin through activity of retrotransposition; some putative allergenic sequences bear fusion products with repeat sequences of transposable elements (LTRs). The abundance of nearby repetitive sequences, activation of transposable elements, and high production of mRNA transcripts appear to coincide in pollen and may contribute to a syndrome in which highly transcribed proteins may be copied and inserted with streamlined features for translation, including grouping and removal of introns.