Kayukawa Takumi, Nagamine Keisuke, Inui Tomohiro, Yokoi Kakeru, Kobayashi Isao, Nakao Hajime, Ishikawa Yukio, Matsuo Takashi
Division of Insect Advanced Technology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8634, Japan.
Faculty of Agriculture, Setsunan University, Hirakata, Osaka 573-0101, Japan.
PNAS Nexus. 2024 Sep 30;3(10):pgae435. doi: 10.1093/pnasnexus/pgae435. eCollection 2024 Oct.
In holometabolous insects, proper control of the production of juvenile hormone (JH), which maintains larval traits, is crucial for successful metamorphosis. JH is produced specifically in the corpora allata (CA) via the functioning of a set of JH biosynthetic enzymes (JHBEs). Expression of JHBE genes in the CA is coordinated except for JH acid methyltransferase (), which functions in the last step of JH biosynthesis. Here, we sought to determine the mechanism that enables this coordinated expression, assuming the presence of a central regulator of JHBE genes. Comparison of transcriptomes in the CA during active and inactive stages revealed the presence of 3 transcription factors, whose expression patterns matched those of JHBE genes. We propose that one of these, Dead ringer (), is the central up-regulator of CA-specific JHBE genes including , based on the following findings: (ⅰ) Knockdown of in the larvae caused precocious metamorphosis, which was rescued by the exogenous application of JH analog, and (ⅱ) knockdown of decreased the expression of most CA-specific JHBE genes examined. Furthermore, RNAi-based reverse genetics indicated that works most upstream in the control of CA-specific JHBE genes, and that shutdown of , which occurs independent of other JHBE genes prior to the onset of metamorphosis, can be hypothetically explained by the presence of an unidentified repressor. Our study suggests that , which has been known to regulate embryonic development in a wide range of animals, is conferred a new role in holometabolous insects, i.e. central regulation of CA-specific JHBE genes.
在全变态昆虫中，正确控制维持幼虫特征的保幼激素（JH）的产生对于成功变态至关重要。JH通过一组保幼激素生物合成酶（JHBEs）的作用在咽侧体（CA）中特异性产生。除了在JH生物合成最后一步起作用的保幼激素酸甲基转移酶外，CA中JHBE基因的表达是协调的。在这里，我们假设存在JHBE基因的中央调节因子，试图确定实现这种协调表达的机制。对CA在活跃和不活跃阶段的转录组进行比较，发现存在3种转录因子，其表达模式与JHBE基因的表达模式相匹配。基于以下发现，我们提出其中一种名为Dead ringer（）的转录因子是包括在内的CA特异性JHBE基因的中央上调调节因子：（ⅰ）幼虫中基因的敲低导致早熟变态，外源性应用JH类似物可挽救这种变态；（ⅱ）基因的敲低降低了所检测的大多数CA特异性JHBE基因的表达。此外，基于RNA干扰的反向遗传学表明，在CA特异性JHBE基因的控制中作用于最上游，并且在变态开始之前独立于其他JHBE基因发生的基因关闭，可以通过存在未鉴定的阻遏物来假设解释。我们的研究表明，已知在广泛的动物中调节胚胎发育的，在全变态昆虫中被赋予了一个新的作用，即CA特异性JHBE基因的中央调节。
