Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China.
Qingdao Agricultural University, Qingdao, 266109, Shandong, China.
BMC Genomics. 2021 Apr 23;22(1):297. doi: 10.1186/s12864-021-07594-2.
Paeonia ostii is a potentially important oilseed crop because its seed yield is high, and the seeds are rich in α-linolenic acid (ALA). However, the molecular mechanisms underlying ALA biosynthesis during seed kernel, seed testa, and fruit pericarp development in this plant are unclear. We used transcriptome data to address this knowledge gap.
Gas chromatograph-mass spectrometry indicated that ALA content was highest in the kernel, moderate in the testa, and lowest in the pericarp. Therefore, we used RNA-sequencing to compare ALA synthesis among these three tissues. We identified 227,837 unigenes, with an average length of 755 bp. Of these, 1371 unigenes were associated with lipid metabolism. The fatty acid (FA) biosynthesis and metabolism pathways were significantly enriched during the early stages of oil accumulation in the kernel. ALA biosynthesis was significantly enriched in parallel with increasing ALA content in the testa, but these metabolic pathways were not significantly enriched during pericarp development. By comparing unigene transcription profiles with patterns of ALA accumulation, specific unigenes encoding crucial enzymes and transcription factors (TFs) involved in de novo FA biosynthesis and oil accumulation were identified. Specifically, the bell-shaped expression patterns of genes encoding SAD, FAD2, FAD3, PDCT, PDAT, OLE, CLE, and SLE in the kernel were similar to the patterns of ALA accumulation in this tissue. Genes encoding BCCP, BC, KAS I- III, and FATA were also upregulated during the early stages of oil accumulation in the kernel. In the testa, the upregulation of the genes encoding SAD, FAD2, and FAD3 was followed by a sharp increase in the concentrations of ALA. In contrast, these genes were minimally expressed (and ALA content was low) throughout pericarp development.
We used three tissues with high, moderate, and low ALA concentrations as an exemplar system in which to investigate tissue-specific ALA accumulation mechanisms in P. ostii. The genes and TFs identified herein might be useful targets for future studies of ALA accumulation in the tree peony. This study also provides a framework for future studies of FA biosynthesis in other oilseed plants.
牡丹皮是一种具有潜在重要性的油料作物，因为它的种子产量高，种子富含α-亚麻酸（ALA）。然而，在这种植物的种子仁、种皮和果实种皮发育过程中，ALA 生物合成的分子机制尚不清楚。我们使用转录组数据来解决这一知识空白。
气相色谱-质谱法表明，ALA 含量在仁中最高，在种皮中中等，在种皮中最低。因此，我们使用 RNA 测序比较了这三种组织中的 ALA 合成。我们鉴定了 227837 条 unigenes，平均长度为 755bp。其中，1371 个基因与脂代谢有关。在仁中油脂积累的早期阶段，脂肪酸（FA）生物合成和代谢途径显著富集。ALA 生物合成在种皮中 ALA 含量增加的同时显著富集，但在种皮发育过程中这些代谢途径没有显著富集。通过比较 unigene 转录谱与 ALA 积累模式，鉴定了与从头 FA 生物合成和油脂积累相关的关键酶和转录因子（TFs）的特定 unigene。具体来说，在仁中，编码 SAD、FAD2、FAD3、PDCT、PDAT、OLE、CLE 和 SLE 的基因的钟形表达模式与该组织中 ALA 积累的模式相似。编码 BCCP、BC、KAS I-III 和 FATA 的基因在仁中油脂积累的早期阶段也被上调。在种皮中，编码 SAD、FAD2 和 FAD3 的基因上调后，ALA 浓度急剧增加。相比之下，这些基因在整个种皮发育过程中表达水平较低（ALA 含量较低）。
我们使用 ALA 浓度高、中、低的三种组织作为范例系统，研究了 P. ostii 中组织特异性 ALA 积累机制。本文鉴定的基因和 TF 可能是未来研究牡丹皮 ALA 积累的有用靶点。本研究还为其他油料植物脂肪酸生物合成的研究提供了框架。
