AUTHOR=Lu Kai , Zhou Jinming , Chen Xia , Li Wenru , Li Yue , Cheng Yibei , Yan Jing , You Keke , Yuan Zhineng , Zhou Qiang 

TITLE=Deficiency of Brummer Impaires Lipid Mobilization and JH-Mediated Vitellogenesis in the Brown Planthopper, Nilaparvata lugens

JOURNAL=Frontiers in Physiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.01535

DOI=10.3389/fphys.2018.01535

ISSN=1664-042X

ABSTRACT=<p>Provisioning of sufficient lipids and vitellogenin to the oocytes is an indispensable process for fecundity of oviparous insects. Acute mobilization of lipid reserves in insects is controlled by the Brummer (Bmm), an orthologous of human adipose triglyceride lipase (ATGL). To investigate the functional roles of brummer-mediated lipolysis in the fecundity of the brown planthopper, <italic>Nilaparvata lugens</italic>, RNA interference (RNAi) analyses were performed with double-stranded RNA (dsRNA) against <italic>NlBmm</italic> in adult females. Knockdown of <italic>NlBmm</italic> expression resulted in obesity and blocked lipid mobilization in the fat body. In addition, <italic>NlBmm</italic> silencing led to retarded ovarian development with immature eggs and less ovarioles, decreased number of laid eggs, prolonged preoviposition period and egg duration. Furthermore, severe reductions of vitellogenin and its receptor abundance were observed upon <italic>NlBmm</italic> knockdown. The transcript levels of <italic>NlJHE</italic> (juvenile hormone esterase) which degrades JH were up-regulated, whereas the expression levels of JH receptors <italic>NlMet</italic> (Methoprene-tolerant) and <italic>NlTai</italic> (Taiman) and their downstream transcription factors <italic>NlKr-h1</italic> (Krüppel-homolog 1) and <italic>NlBr</italic> (Broad-Complex) were down-regulated after suppression of <italic>NlBmm</italic>. JH-deficient females exhibited impaired vitellogenin expression, whereas JH exposure stimulated vitellogenin biosynthesis. Moreover, JH topical application partially rescued the decrease in vitellogenin expression in the <italic>NlBmm</italic>-deficient females. These results demonstrate that brummer-mediated lipolytic system is essential for lipid mobilization and energy homeostasis during reproduction in <italic>N. lugens</italic>. In addition to the classical view of brummer as a direct lipase with lipolysis activity, we propose here that brummer-mediated lipolysis works through JH signaling pathway to activate vitellogenesis and oocyte maturation that in turn regulates female fecundity.</p>