Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
Guangzhou Key Laboratory of Insect Development Regulation and Applied Research, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
BMC Genomics. 2020 Feb 19;21(1):171. doi: 10.1186/s12864-020-6494-3.
Lepidoptera is one group of the largest plant-feeding insects and Spodoptera litura (Lepidoptera: Noctuidae) is one of the most serious agricultural pests in Asia countries. An interesting and unique phenomenon for gonad development of Lepidoptera is the testicular fusion. Two separated testes fused into a single one during the larva-to-pupa metamorphosis, which is believed to contribute to sperm production and the prevalence in field. To study the molecular mechanism of the testicular fusion, RNA sequencing (RNA-seq) experiments of the testes from 4-day-old sixth instar larvae (L6D4) (before fusion), 6-day-old sixth instar larvae (L6D6, prepupae) (on fusing) and 4-day-old pupae (P4D) (after fusion) of S. litura were performed.
RNA-seq data of the testes showed that totally 12,339 transcripts were expressed at L6D4, L6D6 and P4D stages. A large number of differentially expressed genes (DEGs) were up-regulated from L6D4 to L6D6, and then more genes were down-regulated from L6D6 to P4D. The DEGs mainly belongs to the genes related to the 20E signal transduction pathway, transcription factors, chitin metabolism related enzymes, the families of cytoskeleton proteins, extracellular matrix (ECM) components, ECM-related protein, its receptor integrins and ECM-remodeling enzymes. The expression levels of these genes that were up-regulated significantly during the testicular fusion were verified by qRT-PCR. The matrix metalloproteinases (MMPs) were found to be the main enzymes related to the ECM degradation and contribute to the testicular fusion. The testis was not able to fuse if MMPs inhibitor GM6001 was injected into the 5th abdomen region at L6D6 early stage.
The transcriptome and DEGs analysis of the testes at L6D4, L6D6 and P4D stages provided genes expression information related to the testicular fusion in S. litura. These results indicated that cytoskeleton proteins, ECM-integrin interaction genes and ECM-related proteins were involved in cell migration, adhesion and fusion during the testicular fusion. The ECM degradation enzymes MMPs probably play a critical role in the fusion of testis.
鳞翅目是最大的植食性昆虫群体之一，斜纹夜蛾（鳞翅目：夜蛾科）是亚洲国家最严重的农业害虫之一。鳞翅目昆虫在性腺发育过程中存在一种有趣且独特的现象，即睾丸融合。在幼虫到蛹的变态过程中，两个分离的睾丸融合成一个单一的睾丸，这被认为有助于精子的产生和在田间的流行。为了研究睾丸融合的分子机制，对斜纹夜蛾 4 日龄 6 龄幼虫（L6D4）（融合前）、6 日龄 6 龄幼虫（L6D6，预蛹）（融合时）和 4 日龄蛹（P4D）（融合后）的睾丸进行了 RNA 测序（RNA-seq）实验。
睾丸的 RNA-seq 数据显示，L6D4、L6D6 和 P4D 三个阶段共有 12339 个转录本表达。大量差异表达基因（DEGs）从 L6D4 到 L6D6 上调，然后从 L6D6 到 P4D 更多的基因下调。DEGs 主要属于 20E 信号转导途径、转录因子、几丁质代谢相关酶、细胞骨架蛋白家族、细胞外基质（ECM）成分、ECM 相关蛋白、其受体整合素和 ECM 重塑酶相关的基因。通过 qRT-PCR 验证了睾丸融合过程中显著上调的这些基因的表达水平。发现基质金属蛋白酶（MMPs）是 ECM 降解的主要相关酶，有助于睾丸融合。如果在 L6D6 早期向第 5 腹部区域注射 MMPs 抑制剂 GM6001，则睾丸无法融合。
L6D4、L6D6 和 P4D 三个阶段的睾丸转录组和 DEGs 分析提供了斜纹夜蛾睾丸融合相关的基因表达信息。这些结果表明，细胞骨架蛋白、ECM-整合素相互作用基因和 ECM 相关蛋白参与了睾丸融合过程中的细胞迁移、黏附和融合。ECM 降解酶 MMPs 可能在睾丸融合中发挥关键作用。
