Dataset for: Carbonic Anhydrase 2-like in the giant clam, <i>Tridacna squamosa</i>: characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts

The fluted giant clam, <i>Tridacna squamosa</i>, lives in symbiosis with zooxanthellae which reside extracellularly inside a tubular system. Zooxanthellae fix inorganic carbon (C_i) during insolation and donate photosynthate to the host. Carbonic anhydrases catalyze the interconversion of CO₂ and HCO₃^-, of which carbonic anhydrase 2 (CA2) is the most ubiquitous and involved in many biological processes. This study aimed to clone a <i>CA2</i> homolog (<i>CA2-like</i>) from the fleshy and colorful outer mantle as well as the thin and whitish inner mantle of <i>T. squamosa</i>, to determine its cellular and subcellular localization, and to examine the effects of light exposure on its gene and protein expression levels. The cDNA coding sequence of <i>CA2-like</i> from <i>T. squamosa</i> comprised 789 bp, encoding 263 amino acids with an estimated molecular mass of 29.6 kDa. A phenogramic analysis of the deduced CA2-like sequence denoted an animal origin. CA2-like was not detectable in the shell-facing epithelium of the inner mantle adjacent to the extrapallial fluid. Hence, CA2-like is unlikely to participate directly in light-enhanced calcification. By contrast, the outer mantle, which contains the highest density of tertiary tubules and zooxanthellae, displayed high level of <i>CA2-like</i> expression, and CA2-like was localized to the tubule epithelial cells. More importantly, exposure to light induced significant increases in the protein abundance of CA2-like in the outer mantle. Hence, CA2-like could probably take part in the increased supply of inorganic carbon (C_i) from the host clam to the symbiotic zooxanthellae when the latter conduct photosynthesis to fix C_i during light exposure.

鳞砗磲（*Tridacna squamosa*）与虫黄藻（Zooxanthellae）形成共生关系，后者细胞外定位于宿主的管状系统中。虫黄藻在光照过程中固定无机碳（Ci），并将光合产物传递给宿主。碳酸酐酶（Carbonic anhydrases）可催化CO₂与HCO₃⁻之间的相互转化，其中碳酸酐酶2（CA2）分布最为广泛，且参与诸多生物学过程。本研究旨在从鳞砗磲肥厚多彩的外套膜外层以及薄而半透明的外套膜内层中克隆得到CA2同源基因（CA2-like），明确其细胞与亚细胞定位，并探究光照暴露对其基因及蛋白质表达水平的影响。鳞砗磲CA2-like的cDNA编码序列全长789 bp，编码263个氨基酸，预测分子质量为29.6 kDa。对推导得到的CA2-like序列进行系统树分析，结果显示其起源于动物界。在紧邻外套腔液的内套膜面向贝壳的上皮层中未检测到CA2-like的表达，因此CA2-like不太可能直接参与光增强钙化作用。与之相对，外套膜外层拥有密度最高的三级小管与虫黄藻，其CA2-like表达水平显著较高，且CA2-like定位于小管上皮细胞中。更为关键的是，光照暴露可显著提升外套膜外层中CA2-like的蛋白质丰度。据此推测，当虫黄藻在光照条件下进行无机碳固定以完成光合作用时，CA2-like可能参与介导宿主砗磲向共生虫黄藻增加无机碳的供应过程。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于巨蛤（Tridacna squamosa）中碳酸酐酶2类似物（CA2-like）的克隆、定位和功能研究，揭示了其在光暴露下蛋白质表达增加，并可能参与从宿主向共生虫黄藻运输无机碳的过程。数据集包括cDNA序列、分子质量分析以及组织特异性表达数据，支持对共生系统中碳代谢机制的深入理解。