AUTHOR=He Lei , Ou-Yang Yi-Yi , Li Ni , Chen Ying , Liu Shuang-Qing , Huang Guo-Hua 

TITLE=Regulation of Chitinase in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) During Infection by Heliothis virescens ascovirus 3h (HvAV-3h)

JOURNAL=Frontiers in Physiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.00166

DOI=10.3389/fphys.2020.00166

ISSN=1664-042X

ABSTRACT=<p>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 <italic>Spodoptera exigua</italic> (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 <italic>S. exigua chitinase</italic> 7 (<italic>SeCHIT7</italic>) was down-regulated at the 6, 9, 12, 48, 72, and 96 hpi sample times, the <italic>S. exigua chitinase</italic> 11 (<italic>SeCHIT11</italic>) was down-regulated at 3–96 hpi, while both <italic>S. exigua chitinases</italic> (<italic>SeCHIT</italic>s) were up-regulated at 120–168 hpi. Further tissue-specific detection of <italic>SeCHIT7</italic> and <italic>SeCHIT11</italic> transcription showed that <italic>SeCHIT7</italic> was down-regulated at 144 and 168 hpi in the fat body and cuticle. <italic>SeCHIT11</italic> was down-regulated at 168 hpi in the fat body, midgut, and cuticle. Additionally, the transcription and expression of <italic>S. exigua</italic> chitin-binding domain (<italic>SeCBD</italic>) could not be detected in HvAV-3h-infected larvae. The <italic>in vitro</italic> 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 <italic>SeCHIT</italic>s but also affected the normal transcription and expression of <italic>SeCBD</italic> 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.</p>