Abstract
Transcription factors (TFs) play essential roles in the transcriptional regulation of functional genes, and are involved in diverse physiological processes in living organisms. The fruit fly Drosophila melanogaster, a simple and easily manipulated organismal model, has been extensively applied to study the biological functions of TFs and their related transcriptional regulation mechanisms. It is noteworthy that with the development of genetic tools such as CRISPR/Cas9 and the next-generation genome sequencing techniques in recent years, identification and dissection the complex genetic regulatory networks of TFs have also made great progress in other insects beyond Drosophila. However, unfortunately, there is no comprehensive review that systematically summarizes the structures and biological functions of TFs in both model and non-model insects. Here, we spend extensive effort in collecting vast related studies, and attempt to provide an impartial overview of the progress of the structure and biological functions of current documented TFs in insects, as well as the classical and emerging research methods for studying their regulatory functions. Consequently, considering the importance of versatile TFs in orchestrating diverse insect physiological processes, this review will assist a growing number of entomologists to interrogate this understudied field, and to propel the progress of their contributions to pest control and even human health.
Highlights
Transcription factors (TFs) are a plethora of proteins that are present in all living organisms, and they can intricately control transcription of different functional genes in response to internal physiological processes, as well as external environmental stimuli [1,2]
In Aedes aegypti, hormone receptor 3 (HR3), Thanatos-associated protein (THAP) and activating transcription factor-2 (ATF-2) regulate the transcription of Sterol carrier protein 2 (SCP2), which is a critical factor for sterol absorption and transport [93,94]
Our previous studies have shown that high-level resistance to Bacillus thuringiensis (Bt) Cry1Ac toxin in P. xylostella is associated with differential expression of a suite of midgut functional genes, including ALP, ABCC1, ABCC2, ABCC3, and ABCG1, which are trans-regulated by the MAPK signaling pathway [206], and we can speculate that the novel MAPK-mediated trans-regulatory mechanism may be further controlled by diverse downstream TFs such as FOXA [207]
Summary
Transcription factors (TFs) are a plethora of proteins that are present in all living organisms, and they can intricately control transcription of different functional genes in response to internal physiological processes, as well as external environmental stimuli [1,2]. Most eukaryotic TFs with a DNA-binding domain (DBD) are thought to exert regulatory functions by binding to enhancers and recruiting transcriptional complexes or cofactors [7]. According to differences in HTH structure, the HTH superclass can be divided into several classes, including homeodomain, The HTH superclass TFs contain the HTH motif as the DBD. Helices I and II are antiparallel to each other, helices II and III are separated by a β-turn to form a helix-turn-helix (HTH) structure, and helix III functions as the recognition helix for contacting and recognizing specific DNA sequences (Figure 2A). Drosophila contains a total of 103 homeodomain genes, and 54% of TFs are split among families such as paired-like, paired-domain, POU (Pit-Oct-Unc), and LIM proteins that contain other domains for higher binding affinity or protein dimerization, in addition to the homeodomain [21] (Figure 2A)
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