Time-Course Transcriptome Analysis of Compatible and Incompatible Pollen-Stigma Interactions in Brassica napus L.

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.

The molecular signatures of compatible and incompatible pollination

“…To decipher the mechanisms that control reproduction in flowering plants, we extracted the global transcriptomic signatures associated with both pollen and stigmatic cells following their interaction during compatible or incompatible pollination. Although transcriptomes of pollinated stigmas have been recently published 17,18 , these analyses did not try to distinguish between pollen and stigma transcripts. In the present work, we provide a comprehensive transcriptomic dataset for stigma-pollen interactions using a novel SNP-based analysis.…”

“…Recently, Zhang et al 18 performed a time course transcriptome analysis of compatible and incompatible reaction in Brassica napus . They speculated that compatible responses had close parallels with plant-pathogen interactions, mainly with effector-triggered susceptibility, while incompatible response rather resembled effector-triggered immunity, and that PTI could be common to both compatible and incompatible responses.…”

“…The similarity between the stigma-pollen interaction and plant-pathogen interaction has been discussed and has drawn researchers’ attention for a long time 10,42–44 . Several transcriptomic analyses of pollinated stigmas/pistils reported enrichment in transcripts linked to stress or defense response in female tissues 18,20,33,44,45 . Tung et al and Leydon et al suggested that such defense-related genes would have function in pollination.…”

“…To get a global picture of the early fertilization events with no a priori, transcriptome approaches were also conducted. The main goal was to draw up catalogues of genes modulated during pollination so as to unravel the stigmatic response to compatible or incompatible pollen 8,15–18 . However, the main drawback of these approaches was the difficulty in accurately distinguishing between pollen and stigma derived transcripts.…”

Genetic and Cytological Analyses of the Natural Variation of Seed Number per Pod in Rapeseed (Brassica napus L.)

“…It should be noted that both the maternal and xenia effects for 12 crosses have comparable contributions on SNPP. This might be caused by the disharmony between the pollen grain/pollen tube including the sperm cells with the various sporophytic maternal tissues and the cells of the female gametophyte (Dresselhaus and Franklin-Tong, 2013; Bleckmann et al, 2014; Zhang et al, 2017). In addition, analysis of the data using the diploid seed embryo–cytoplasmic–maternal (2nGoCGm) model (Zhu, 1997) further showed that the natural variation of SNPP was mainly governed by maternal genotype and embryo effects, followed by a small cytoplasm effect.…”