Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan.
Plant Cell Rep. 2021 Oct;40(10):1859-1874. doi: 10.1007/s00299-021-02750-0. Epub 2021 Jul 14.
CAP biosynthesis in the pericarp of chili pepper fruits occurs with an ambiguous boundary in the placental septum and pericarp. Capsaicinoid (CAP) is a pungent ingredient of chili pepper fruits. Generally, CAP biosynthesis is limited to the placental septum of fruits, but it has been reported that its biosynthesis occurs even in the pericarp of some extremely pungent varieties, resulting in a substantial increase in total content. To examine the mechanism of CAP biosynthesis in the pericarp, comparative transcriptome analysis of a variety that produces CAP in the pericarp (MY) and a variety that does not (HB) was carried out. RNA-seq revealed that 2264 genes were differentially expressed in the MY pericarp compared with the HB pericarp. PCA analysis and GO enrichment analysis indicated that the MY pericarp has a gene expression profile more like placental septum than the HB pericarp. The gene expression of CAP biosynthesis-related genes in the MY pericarp changed coordinately with the placental septum during fruit development. In most Capsicum accessions including HB, the distribution of slender epidermal cells producing CAP was limited to the placental septum, and the morphological boundary between the placental septum and pericarp was clear. In some extremely pungent varieties such as MY, slender epidermal cells ranged from the placental septum to the pericarp region, and the pericarp was morphologically similar to the placental septum, such as the absence of large sub-epidermal cells and abundant spaces in the parenchymal tissue. Our data suggest that CAP biosynthesis in the pericarp occurred with an ambiguous boundary in the placental septum and pericarp. These findings contribute to further enhancement of CAP production in chili pepper fruits.
辣椒果皮中 CAP 的生物合成与胎座隔膜和果皮之间的不明确边界有关。辣椒素（CAP）是辣椒果实的一种辛辣成分。通常，CAP 的生物合成仅限于果实的胎座隔膜，但已有报道称，其生物合成甚至发生在一些极其辛辣的品种的果皮中，导致总含量大幅增加。为了研究果皮中 CAP 生物合成的机制，对一种在果皮中产生 CAP 的品种（MY）和一种不产生 CAP 的品种（HB）进行了比较转录组分析。RNA-seq 显示，与 HB 果皮相比，MY 果皮中有 2264 个基因差异表达。PCA 分析和 GO 富集分析表明，MY 果皮的基因表达谱更类似于胎座隔膜，而 HB 果皮则更类似于果皮。MY 果皮中 CAP 生物合成相关基因的表达在果实发育过程中与胎座隔膜协调变化。在包括 HB 在内的大多数辣椒品种中，产生 CAP 的细长表皮细胞的分布仅限于胎座隔膜，胎座隔膜和果皮之间的形态边界清晰。在一些极其辛辣的品种中，如 MY，细长表皮细胞从胎座隔膜延伸到果皮区域，果皮在形态上类似于胎座隔膜，例如缺乏大的表皮下细胞和丰富的薄壁组织中的空间。我们的数据表明，CAP 在果皮中的生物合成与胎座隔膜和果皮之间的不明确边界有关。这些发现有助于进一步提高辣椒果实中 CAP 的产量。
