Key Laboratory of Saline-Alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Sciences, Northeast Forestry University, Harbin 150040, China.
20/20 Seed Labs Inc., Nisku, AB T9E 7N5, Canada.
Int J Mol Sci. 2022 Oct 28;23(21):13102. doi: 10.3390/ijms232113102.
In Brassicaceae, the papillary cells of the stigma are the primary site of the self-incompatibility (SI) responses. SI preserves the genetic diversity by selectively rejecting irrelevant or incompatible pollen, thus promoting cross fertilization and species fitness. Mechanisms that regulate SI responses in have been studied mainly on the mature stigma that often undermines how stigma papillary cells attain the state of SI during development. To understand this, we integrated PacBio SMRT-seq with Illumina RNA-seq to construct a de novo full-length transcriptomic database for different stages of stigma development in ornamental kale. A total of 48,800 non-redundant transcripts, 31,269 novel transcripts, 24,015 genes, 13,390 alternative splicing, 22,389 simple sequence repeats, 21,816 complete ORF sequences, and 4591 lncRNAs were identified and analyzed using PacBio SMRT-seq. The Illumina RNA-seq revealed 15,712 differentially expressed genes (DEGs) and 8619 transcription factors. The KEGG enrichment analysis of 4038 DEGs in the "incompatibility" group revealed that the flavonoid and fatty acid biosynthesis pathways were significantly enriched. The cluster and qRT-PCR analysis indicated that 11 and 14 candidate genes for the flavonoid and fatty acid biosynthesis pathways have the lowest expression levels at stigma maturation, respectively. To understand the physiological relevance of the downregulation of fatty acid biosynthesis pathways, we performed inhibitor feeding assays on the mature stigma. The compatible pollination response was drastically reduced when mature stigmas were pre-treated with a fatty acid synthase inhibitor. This finding suggested that fatty acid accumulation in the stigmas may be essential for compatible pollination and its downregulation during maturity must have evolved as a support module to discourage the mounting of self-incompatible pollen.
在十字花科植物中，柱头的乳突细胞是自交不亲和（SI）反应的主要部位。SI 通过选择性地拒绝不相关或不相容的花粉来保护遗传多样性，从而促进异花授粉和物种适应。在 中调节 SI 反应的机制主要在成熟的柱头上进行研究，这往往破坏了柱头乳突细胞在发育过程中如何达到 SI 状态。为了理解这一点，我们将 PacBio SMRT-seq 与 Illumina RNA-seq 相结合，构建了观赏羽衣甘蓝柱头不同发育阶段的从头转录组数据库。总共鉴定和分析了 48800 个非冗余转录本、31269 个新转录本、24015 个基因、13390 个可变剪接、22389 个简单序列重复、21816 个完整 ORF 序列和 4591 个 lncRNA。Illumina RNA-seq 揭示了 15712 个差异表达基因（DEGs）和 8619 个转录因子。“不相容性”组中 4038 个 DEGs 的 KEGG 富集分析表明，黄酮类和脂肪酸生物合成途径显著富集。聚类和 qRT-PCR 分析表明，黄酮类和脂肪酸生物合成途径的 11 个和 14 个候选基因在柱头成熟时表达水平最低。为了了解脂肪酸生物合成途径下调的生理相关性，我们在成熟的柱头上进行了抑制剂喂养实验。当成熟的柱头用脂肪酸合酶抑制剂预处理时，相容的授粉反应大大降低。这一发现表明，脂肪酸在柱头上的积累可能对相容的授粉至关重要，而在成熟过程中其下调必须作为一个支持模块进化而来，以阻止自交花粉的积累。
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