Abstract
Brassica species exhibit both compatible and incompatible pollen-stigma interactions, however, the underlying molecular mechanisms remain largely unknown. Here, RNA-seq technology was applied in a comprehensive time-course experiment (2, 5, 10, 20, and 30 min) to explore gene expression during compatible/incompatible pollen-stigma interactions in stigma. Moderate changes of gene expression were observed both in compatible pollination (PC) and incompatible pollination (PI) within 10 min, whereas drastic changes showed up by 30 min, especially in PI. Stage specific DEGs [Differentially Expressed Gene(s)] were identified, and signaling pathways such as stress response, defense response, cell wall modification and others were found to be over-represented. In addition, enriched genes in all samples were analyzed as well, 293 most highly expressed genes were identified and annotated. Gene Ontology and metabolic pathway analysis revealed 10 most highly expressed genes and 37 activated metabolic pathways. According to the data, downstream components were activated in signaling pathways of both compatible and incompatible responses, and incompatible response had more complicated signal transduction networks. This study provides more detailed molecular information at different time points after compatible and incompatible pollination, deepening our knowledge about pollen-stigma interactions.
Highlights
The proper interactions between pollen and stigma play a vital role in successful pollination which is the key process in reproduction for angiosperms
When pollen of “W-3” was applied to the stigma of “Westar,” 23 pollen grains were observed being captured by the stigma papilla cell but there was no change in morphology of the pollen (Figure 1A, left panel)
It could be deduced that it was possible for a compatible pollen grain to have experienced all initial steps of pollen-stigma interaction during the first 30 min following compatible pollination; incompatible pollen exhibited the first two steps in the same time period
Summary
The proper interactions between pollen and stigma play a vital role in successful pollination which is the key process in reproduction for angiosperms. The Brassicaceae plants have evolved complicated and elaborate mechanisms for successful fertilization to produce vigorous progenies. These mechanisms involve blocking the adherence and growth of inter-species pollen, rejecting “self ” pollen (self-incompatibility, SI) and only allowing the fertilization of compatible pollen with different genetic background. Once compatible pollen lands on the stigma, a series of signaling events are triggered.
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