He Lei, Ou-Yang Yi-Yi, Li Ni, Chen Ying, Liu Shuang-Qing, Huang Guo-Hua
Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha, China.
College of Plant Protection, Hunan Agricultural University, Changsha, China.
Front Physiol. 2020 Mar 10;11:166. doi: 10.3389/fphys.2020.00166. eCollection 2020.
Insect chitinases play essential roles in the molting and metamorphosis of insects. The virus Heliothis virescens ascovirus 3h (HvAV-3h) can prolong the total duration of the larval stage in its host larvae. In this study, the molecular character and function of chitinase and chitin-binding domain (CBD) were analyzed in larvae of (Hübner) (Lepidoptera: Noctuidae). In detecting the chitinase activity of mock-infected and HvAV-3h-infected larval whole bodies and four different larval tissues, the results showed that larval chitinase activity was significantly decreased at 48 h post infection (hpi) and that the chitinase activity of HvAV-3h-infected larval fat body and cuticle was notably decreased at 144 and 168 hpi. The transcription level of 7 () was down-regulated at the 6, 9, 12, 48, 72, and 96 hpi sample times, the 11 () was down-regulated at 3-96 hpi, while both (s) were up-regulated at 120-168 hpi. Further tissue-specific detection of and transcription showed that was down-regulated at 144 and 168 hpi in the fat body and cuticle. was down-regulated at 168 hpi in the fat body, midgut, and cuticle. Additionally, the transcription and expression of chitin-binding domain () could not be detected in HvAV-3h-infected larvae. The analyses of SeCHIT7N, SeCHIT11, and SeCBD showed that SeCHIT7N and SeCHIT11 were typical chitinases. Conversely, no chitinase activity was detected with SeCBD. SeCBD, however, could significantly increase the activity of SeCHIT7N and SeCHIT11. In conclusion, HvAV-3h not only interfered with the transcription and expression of s but also affected the normal transcription and expression of and, in doing so, influenced the host larval chitinase activity. These results will aid in providing a foundation for further studies on the pathogenesis of HvAV-3h.
昆虫几丁质酶在昆虫的蜕皮和变态过程中发挥着重要作用。病毒棉铃虫杆状病毒3h（HvAV-3h）可延长其宿主幼虫的幼虫期总时长。在本研究中，对烟青虫（Hübner）（鳞翅目：夜蛾科）幼虫的几丁质酶和几丁质结合结构域（CBD）的分子特征及功能进行了分析。在检测 mock 感染和 HvAV-3h 感染的幼虫整体及四种不同幼虫组织的几丁质酶活性时，结果显示感染后48小时（hpi）幼虫几丁质酶活性显著降低，且在144和168 hpi时，HvAV-3h感染的幼虫脂肪体和表皮的几丁质酶活性显著降低。SeCHIT7（7种（））的转录水平在6、9、12、48、72和96 hpi采样时间下调，SeCHIT11（11种（））在3至96 hpi下调，而两者（多种（））在120至168 hpi上调。对SeCHIT7和SeCHIT11的进一步组织特异性转录检测表明，在144和168 hpi时脂肪体和表皮中的SeCHIT7下调。在168 hpi时脂肪体、中肠和表皮中的SeCHIT11下调。此外，在HvAV-3h感染的幼虫中未检测到几丁质结合结构域（SeCBD）的转录和表达。对SeCHIT7N、SeCHIT11和SeCBD的分析表明，SeCHIT7N和SeCHIT11是典型的几丁质酶。相反，未检测到SeCBD的几丁质酶活性。然而，SeCBD可显著提高SeCHIT7N和SeCHIT11的活性。总之，HvAV-3h不仅干扰了几丁质酶的转录和表达，还影响了SeCHIT7和SeCHIT11的正常转录和表达，进而影响宿主幼虫的几丁质酶活性。这些结果将有助于为进一步研究HvAV-3h的发病机制提供基础。
