Tissue-specific endopolyploidy is widespread among plants and animals and its role in organ development and function has long been investigated. In insects, the fat body cells of sexually mature females produce substantial amounts of egg yolk precursor proteins (vitellogenins) and exhibit high polyploid levels, which is considered crucial for boosting egg production. Termites are social insects with a reproductive division of labor, and the fat bodies of mature termite queens exhibit higher ploidy levels than those of other females. The fat bodies of mature termite queens are known to be histologically and cytologically specialized in protein synthesis. However, the relationship between such modifications and polyploidization remains unknown. In this study, we investigated the relationship among cell type, queen maturation, and ploidy levels in the fat body of the termite Reticulitermes speratus. We first confirmed that the termite fat body consists of two types of cells, that is, adipocytes, metabolically active cells, and urocytes, urate-storing cells. Our ploidy analysis using flow cytometry has shown that the fat bodies of actively reproducing queens had more polyploid cells than those of newly emerged and pre-reproductive queens, regardless of the queen phenotype (adult or neotenic type). Using image-based analysis, we found that not urocytes, but adipocytes became polyploid during queen differentiation and subsequent sexual maturation. These results suggest that polyploidization in the termite queen fat body is associated with sexual maturation and is regulated in a cell type-specific manner. Our study findings have provided novel insights into the development of insect fat bodies and provide a basis for future studies to understand the functional importance of polyploidy in the fat bodies of termite queens.

中文翻译：

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白蚁蚁后皇家脂肪体中细胞类型特异性多倍化

组织特异性内多倍体在植物和动物中广泛存在，其在器官发育和功能中的作用早已被研究。在昆虫中，性成熟雌性的脂肪体细胞产生大量的蛋黄前体蛋白（卵黄原蛋白）并表现出高多倍体水平，这被认为对于提高产蛋量至关重要。白蚁是具有生殖分工的社会性昆虫，成熟白蚁蚁后的脂肪体比其他雌性表现出更高的倍性水平。已知成熟白蚁蚁后的脂肪体在组织学和细胞学上专门用于蛋白质合成。然而，这种修饰和多倍化之间的关系仍然未知。在这项研究中，我们研究了散白蚁脂肪体中细胞类型、蚁后成熟和倍性水平之间的关系。我们首先证实白蚁脂肪体由两种类型的细胞组成，即脂肪细胞（代谢活跃的细胞）和尿细胞（储存尿酸盐的细胞）。我们使用流式细胞术进行的倍性分析表明，无论蜂王表型如何（成年型或幼态型），活跃繁殖的蜂王的脂肪体比新出现的和预繁殖蜂王的脂肪体具有更多的多倍体细胞。使用基于图像的分析，我们发现在蜂王分化和随后的性成熟过程中，脂肪细胞而不是尿细胞变成多倍体。这些结果表明，白蚁蚁后脂肪体内的多倍化与性成熟相关，并以细胞类型特异性的方式进行调节。我们的研究结果为昆虫脂肪体的发育提供了新的见解，并为未来研究了解白蚁蚁后脂肪体中多倍体的功能重要性提供了基础。