Agricultural college, Henan University of Science and Technology, 471023, Luoyang, Henan, China.
National Peony Gene Bank, 471011, Luoyang, Henan, China.
BMC Genomics. 2023 Nov 3;24(1):665. doi: 10.1186/s12864-023-09730-6.
Tree peony (Paeonia sect. Moutan DC.) is a famous flower native to China with high ornamental, medicinal, and oil value. However, the low regeneration rate of callus is one of the main constraints for the establishment of a genetic transformation system in tree peony. By histomorphological observation, transcriptomic analysis and metabolite determination, we investigated the molecular mechanism of somatic embryogenesis after the establishment of a culture system and the induction of somatic embryo(SE) formation.
We found that SE formation was successfully induced when cotyledons were used as explants. A total of 3185 differentially expressed genes were screened by comparative transcriptomic analysis of embryogenic callus (EC), SE, and non-embryogenic callus (NEC). Compared to NEC, the auxin synthesis-related genes GH3.6 and PCO2 were up-regulated, whereas cytokinin dehydrogenase (CKX6) and CYP450 family genes were down-regulated in somatic embryogenesis. In SE, the auxin content was significantly higher than the cytokinin content. The methyltransferase-related gene S-adenosylmethionine synthase (SAMS) and the flavonoid biosynthesis-related gene (ANS and F3'5'H) were down-regulated in somatic embryogenesis. The determination of flavonoids showed that rhoifolin and hyperoside had the highest content in SE. The results of transcriptome analysis were consistent with the relative expression of 8 candidate genes by quantitative polymerase chain reaction analysis.
The results revealed that auxin and cytokinin may play a key role in 'Fengdan' somatic embryogenesis. The genes related to somatic embryogenesis were revealed, which has partly elucidated the molecular mechanism of somatic embryogenesis in 'Fengdan'.
牡丹（芍药属牡丹组 DC.）是中国特有的著名花卉，具有很高的观赏、药用和油用价值。然而，愈伤组织的低再生率是建立牡丹遗传转化体系的主要限制因素之一。通过组织形态学观察、转录组分析和代谢物测定，我们研究了牡丹建立培养体系后体细胞胚胎发生和体细胞胚形成的分子机制。
我们发现，以子叶为外植体可成功诱导胚状体形成。通过比较胚性愈伤组织（EC）、胚状体（SE）和非胚性愈伤组织（NEC）的转录组分析，共筛选出 3185 个差异表达基因。与 NEC 相比，体细胞胚胎发生中生长素合成相关基因 GH3.6 和 PCO2 上调，细胞分裂素脱氢酶（CKX6）和 CYP450 家族基因下调。在 SE 中，生长素含量明显高于细胞分裂素含量。甲基转移酶相关基因 S-腺苷甲硫氨酸合成酶（SAMS）和类黄酮生物合成相关基因（ANS 和 F3'5'H）在体细胞胚胎发生中下调。类黄酮的测定表明，SE 中 rhoifolin 和 hyperoside 的含量最高。转录组分析结果与 8 个候选基因的定量聚合酶链反应分析相对表达一致。
结果表明，生长素和细胞分裂素可能在‘凤丹’体细胞胚胎发生中起关键作用。揭示了与体细胞胚胎发生相关的基因，部分阐明了‘凤丹’体细胞胚胎发生的分子机制。
