Number of putative intronization and de-intronization events in fission yeasts.

aUnable to distinguish between intronization and de-intronization because of a lack of outgroup evidence.bFor intronization, “Supported by transcriptome data” means that the novel intron region is spliced in at least one transcript. “Disproved by transcriptome data” means that the novel intron region is retained in all the related transcripts. For de-intronization, “Supported by transcriptome data” means the novel exon region is retained in at least one transcript. “Disproved by transcriptome data” means the novel exon region is spliced in all transcripts and is thus an unannotated intron. If no transcripts cover the novel intron or exon region, it is defined as “Lacking related transcript data”.a. 由于缺乏外类群证据（outgroup evidence），无法区分内含子化（intronization）与去内含子化（de-intronization）。针对内含子化事件，"转录组数据（transcriptome data）支持"表示该新内含子区域可在至少一条转录本中被剪接移除；"转录组数据不支持"则表示该新内含子区域在所有相关转录本中均被保留。针对去内含子化事件，"转录组数据支持"表示该新外显子区域可在至少一条转录本中被保留；"转录组数据不支持"表示该新外显子区域在所有转录本中均被剪接移除，因此属于未注释的内含子。若无转录本覆盖该新内含子或外显子区域，则将其定义为"缺乏相关转录组数据"。