Pleiotropic Functions of <i>FoxN1</i>: Regulating Different Target Genes during Embryogenesis and Nymph Molting in the Brown Planthopper

• Main Authors: Yu-Xuan Ye, Chuan-Xi Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: International Journal of Molecular Sciences
• Subjects: FoxN1; brown planthopper; pleiotropism; embryogenesis; keratin gene
• Online Access: https://www.mdpi.com/1422-0067/21/12/4222

<i>FoxN1</i> gene belongs to the forkhead box gene family that comprises a diverse group of “winged helix” transcription factors that have been implicated in a variety of biochemical and cellular processes. In the brown planthopper (BPH), <i>FoxN1</i> is highly expressed in the ovaries and newly laid eggs, where it acted as an indispensable gene through its molecular targets to regulate early embryonic development. Moreover, the results of the RNAi experiments indicated that <i>Nilaparvata</i><i> </i><i>lugens</i> <i>FoxN1</i> (<i>NlFoxN1</i>) exhibited pleiotropism: they not only affected the embryogenesis, but also played an important role in molting. RNA-seq and RNAi were further used to reveal potential target genes of <i>NlFox</i><i>N1</i> in different stages. In the eggs, ten downregulated genes were defined as potential target genes of <i>NlFox</i><i>N1</i> because of the similar expression patterns and functions with <i>NlFoxN1</i>. Knockdown of <i>NlFox</i><i>N1</i> or any of these genes prevented the development of the eggs, resulting in a zero hatchability. In the nymphs, <i>Nl</i><i>FoxN1</i> regulated the expression of a keratin gene, type I cytoskeletal keratin 9 (<i>NlKrt9</i>), to participate in the formation of an intermediate filament framework. Depletion of <i>Nl</i><i>FoxN1</i> or <i>NlKrt9</i> in nymphs, BPHs failed to shed their old cuticle during nymph-to-nymph or nymph-to-adult molting and the mortality was almost 100%. Altogether, the pleiotropic roles of<i> Nl</i><i>FoxN1</i> during embryogenesis and nymph molting were supported by the ability to coordinate the temporal and spatial gene expression of their target genes.