# Functional Characterization of Akt, a Serine/Threonine Kinase, in Tuta absoluta: A Key Regulator of Molting, Hormones, and Reproduction with Potential for RNAi Pest Control

## TL;DR

This study identifies a key gene in tomato leafminer pests that controls growth and reproduction, offering a potential RNAi-based pest control strategy.

## Contribution

The study demonstrates that TaAkt is a pleiotropic regulator of metamorphosis and reproduction in Tuta absoluta, making it a novel target for RNAi pest control.

## Key findings

- Silencing TaAkt caused pupal mortality, defective molting, and reduced chitin content.
- TaAkt knockdown in females led to impaired ovarian growth, reduced hormone levels, and lower egg hatching rates.
- TaAkt is a promising target for RNAi-based pest control to suppress both survival and reproduction.

## Abstract

The tomato leafminer is a globally destructive pest that inflicts substantial damage on tomato crops, causing significant economic losses. A comprehensive understanding of the biological mechanisms regulating its growth and reproduction is crucial for the development of sustainable pest management strategies. This study focused on a key gene, Akt, which acts as a central switch in the insect’s growth and reproductive systems. We identified and characterized the Akt gene (TaAkt) and then reduced its activity using RNA interference (RNAi). Silencing of TaAkt resulted in severe developmental abnormalities: numerous pupae failed to metamorphose into adults, exhibiting weakened body structure, and experienced disruptions in hormone levels that control molting and growth. In female insects, TaAkt knockdown led to underdeveloped ovaries, fewer eggs, and lower hatching success. These findings underscore the role of TaAkt in the regulation of growth and reproduction in the tomato leafminer. Targeting this single gene presents a promising approach for the development of innovative, environmentally sustainable pest control strategies that reduce both the survival and reproductive ability of these insects without relying on chemical pesticides.

Insect insulin signaling plays a central role in regulating development, metamorphosis, and reproduction, yet its mechanistic functions in the tomato leafminer, Tuta absoluta, a globally significant pest, remain poorly understood. This study aimed to elucidate the role of the serine/threonine kinase Akt (TaAkt) in coordinating metamorphosis and female reproductive processes. The TaAkt gene was cloned and characterized, and its spatiotemporal expression was analyzed across various developmental stages and tissues. RNA interference (RNAi) was employed to knock down TaAkt in late pupae and newly emerged females, followed by assessment of pupal-adult eclosion, chitin metabolism, 20-hydroxyecdysone (20E) titer, ovarian development, juvenile hormone (JH) levels, vitellogenin synthesis, and fecundity. Knockdown of TaAkt significantly reduced 20E titers and downregulated the expression of ecdysone biosynthesis and signaling genes, leading to pupal mortality, defective molting, and reduced chitin content. In adult females, TaAkt silencing impaired ovarian growth, decreased JH levels, suppressed vitellogenin production, and reduced egg number and hatching rates. These findings demonstrate that TaAkt exerts pleiotropic control over both metamorphic and reproductive processes in T. absoluta. The study identifies TaAkt as a promising molecular target for RNAi-based pest management strategies, offering a potential approach to simultaneously suppress survival and reproductive capacity in this economically important pest.