Intestinal absorption is essential for heterotrophic bilaterians with a tubular gut. Although the fundamental features of the digestive system were shared among chordates with evolution, the gut morphologies of vertebrates diverged and adapted to different food habitats. The ascidian Ciona intestinalis type A, a genome-wide research model of basal chordates, is used to examine the functional morphology of the intestines because of its transparent juvenile body. In the present study, the characteristic gene expression patterns (GEP) of Ciona absorptive proteins, e.g., brush border membrane enzymes for terminal digestion (lactase, maltase, APA, and APN) and transporters (SGLT1, GLUT5, PEPT1, and B⁰AT1), were investigated in juveniles and young adults, with a special reference to the absorption of other nutrients by pinocytosis- and phagocytosis-related proteins (megalin, cubilin, amnionless, Dab2, Rab7, LAMP, cathepsins, and MRC1). Whole-mount in situ hybridization revealed that these GEP showed multi-regional and repetitive features along the Ciona gastrointestinal tract, mainly in the stomach and several regions of the intestines. In young adults, many absorption-related genes, including pinocytosis-/phagocytosis-related genes, were also expressed between the stomach and mid-intestine. In the gastrointestinal epithelium, absorption-related genes showed zonal GEP along the epithelial structure. Comparisons of GEP, including other intestinal functions, such as nutrient digestion and intestinal protection, indicated the repetitive assignment of a well-coordinated set of intestinal GEP in the Ciona gastrointestinal tract.

肠道吸收对于具有管状肠道的异养两侧对称动物至关重要。尽管消化系统的基本特征在进化过程中脊索动物之间是相同的，但脊椎动物的肠道形态却存在差异并适应不同的食物栖息地。海鞘Ciona Enteris A型是一种基础脊索动物的全基因组研究模型，因其幼年体透明而被用来检查肠道的功能形态。在本研究中，海鞘吸收蛋白的特征基因表达模式（GEP），例如用于末端消化的刷状缘膜酶（乳糖酶、麦芽糖酶、APA和APN）和转运蛋白（SGLT1、GLUT5、PEPT1和B 0 ^AT1） ），在青少年和年轻人中进行了研究，特别关注胞饮作用和吞噬作用相关蛋白（megalin、cubilin、amnionless、Dab2、Rab7、LAMP、组织蛋白酶和 MRC1）对其他营养物质的吸收。整体原位杂交显示，这些 GEP 在海鞘胃肠道上表现出多区域和重复特征，主要是在胃和肠道的几个区域。在年轻人中，许多吸收相关基因，包括胞饮作用/吞噬作用相关基因，也在胃和中肠之间表达。在胃肠道上皮中，吸收相关基因沿着上皮结构呈现带状 GEP。GEP 的比较，包括其他肠道功能，如营养物消化和肠道保护，表明海鞘胃肠道中一组协调良好的肠道 GEP 的重复分配。