Catecholamines (CAs) play critical roles in regulating physiological and immunological homeostasis in invertebrates and vertebrates under stressful environments. DOPA decarboxylase (DDC), an enzyme responsible for the decarboxylation step of dopamine synthesis, participates in neurotransmitter metabolism and innate immunity. In shrimp, two genes encoding CA-related enzymes, tyrosine hydroxylase and dopamine beta-hydroxylase, were further identified and characterized as neuroendocrine-immune regulators. In this study, full-length complementary DNA of DDC cloned from the thoracic ganglia of shrimp, Litopenaeus vannamei, (LvDDC) was predicted to encode a 452-amino acid protein with a pyridoxal-dependent decarboxylase-conserved domain, and this deduced protein of LvDDC was phylogenetically closely related to insect DDC. LvDDC messenger RNA expression was analyzed by a semiquantitative RT-PCR and a real-time quantitative RT-PCR and found to be abundant in the hepatopancreas and nervous system but at low levels in haemocytes, heart, stomach, and gills. To determine the role of LvDDC, double-stranded (ds)RNA was used for in vivo assessments. LvDDC-depleted shrimp revealed significant increases in the total haemocyte count, hyaline cells, granular cells, phenoloxidase activity, and respiratory bursts of haemocytes per unit of haemolymph, and phagocytic activity and clearance efficiency toward Vibrio alginolyticus. Further, decreased LvDDC mRNA expression was accompanied by decreases in dopamine, glucose, and lactate levels in haemolymph. In shrimp that received LvDDC-dsRNA for 3 days and were then challenged with V. alginolyticus, the survival rate of LvDDC-depleted shrimp was significantly higher than that of shrimp that received diethyl pyrocarbonate-water or non-targeted dsRNA. In conclusion, the cloned LvDDC was responsible for controlling dopamine synthesis, which then regulated physiological and immune responses in L. vannamei.

儿茶酚胺 (CA) 在压力环境下调节无脊椎动物和脊椎动物的生理和免疫稳态方面发挥着关键作用。多巴脱羧酶 (DDC) 是一种负责多巴胺合成脱羧步骤的酶，参与神经递质代谢和先天免疫。在虾中，两种编码 CA 相关酶的基因，酪氨酸羟化酶和多巴胺 β-羟化酶，被进一步鉴定并表征为神经内分泌免疫调节剂。在这项研究中，从南美白对虾的胸神经节中克隆出 DDC 的全长互补 DNA, (LvDDC) 被预测编码一个 452 个氨基酸的蛋白质，具有依赖于吡哆醛的脱羧酶保守结构域，并且这种推断的 LvDDC 蛋白质在系统发育上与昆虫 DDC 密切相关。LvDDC 信使 RNA 表达通过半定量 RT-PCR 和实时定量 RT-PCR 进行分析，发现在肝胰腺和神经系统中含量丰富，但在血细胞、心脏、胃和鳃中含量较低。为了确定 LvDDC 的作用，双链 (ds) RNA 用于体内评估。去除 LvDDC 的虾显示血细胞总数、透明细胞、颗粒细胞、酚氧化酶活性和每单位血淋巴血细胞的呼吸爆发，以及对溶藻弧菌的吞噬活性和清除效率显着增加. 此外，LvDDC mRNA 表达的降低伴随着血淋巴中多巴胺、葡萄糖和乳酸水平的降低。在接受 LvDDC-dsRNA 3 天，然后用溶藻弧菌攻击的虾中，去除 LvDDC 的虾的存活率显着高于接受焦碳酸二乙酯-水或非靶向 dsRNA 的虾。总之，克隆的 LvDDC 负责控制多巴胺合成，然后调节南美白对虾的生理和免疫反应。