Ragweed (Ambrosia artemisiifolia) pollen allergenicity: SuperSAGE transcriptomic analysis upon elevated CO2 and drought stress

摘要

Background Pollen of common ragweed (Ambrosia artemisiifolia) is a main cause of allergic diseases in Northern America. The weed has recently become spreading as a neophyte in Europe, while climate change may also affect the growth of the plant and additionally may also influence pollen allergenicity. To gain better insight in the molecular mechanisms in the development of ragweed pollen and its allergenic proteins under global change scenarios, we generated SuperSAGE libraries to identify differentially expressed transcripts. Results Ragweed plants were grown in a greenhouse under 380?ppm CO₂ and under elevated level of CO₂ (700?ppm). In addition, drought experiments under both CO₂ concentrations were performed. The pollen viability was not altered under elevated CO₂, whereas drought stress decreased its viability. Increased levels of individual flavonoid metabolites were found under elevated CO₂ and/or drought. Total RNA was isolated from ragweed pollen, exposed to the four mentioned scenarios and four SuperSAGE libraries were constructed. The library dataset included 236,942 unique sequences, showing overlapping as well as clear differently expressed sequence tags (ESTs). The analysis targeted ESTs known in Ambrosia, as well as in pollen of other plants. Among the identified ESTs, those encoding allergenic ragweed proteins (Amb a) increased under elevated CO₂ and drought stress. In addition, ESTs encoding allergenic proteins in other plants were also identified. Conclusions The analysis of changes in the transcriptome of ragweed pollen upon CO₂ and drought stress using SuperSAGE indicates that under global change scenarios the pollen transcriptome was altered, and impacts the allergenic potential of ragweed pollen.