International Journal of Marine Science, 2025, Vol.15, No.3, 167-178 http://www.aquapublisher.com/index.php/ijms 172 induction pathway represented by the IGF and mTOR pathways are the most critical. IGF signaling functions similarly to vertebrates in invertebrates, regulating individual growth and tissue development. Multiple IGF signaling component genes have been identified in abalone: such as IGF-I, IGF receptors and binding proteins. Among them, IGF binding protein-5 (IGFBP-5) is highly expressed in Ezo abalone nerves and gonads, and is believed to regulate growth and gonad development. When the IGFBP-5 gene is knocked down, the growth of abalone embryos and larvae is inhibited, showing the importance of IGF signaling for the onogeny of abalone. The IGF signal activates the mTOR pathway through the downstream AKT. mTOR is a central regulator of cellular trophic and energy states that play a central role in abalone anabolic. Liu et al. (2021) found that arginine upregulates the activity of the abalone TOR pathway by activating the lysosomal membrane protein SLC38A9, promoting protein synthesis and growth. In addition, starvation and refeeding experiments show that the activity of the abalone mTOR pathway changes with the nutritional state. Short-term starvation will reduce the S6K phosphorylation level downstream of the TOR, inhibit anabolicity, and thus temporarily slow growth. After the resumption of feeding, mTOR is activated rapidly, cell proliferation and protein synthesis are accelerated, and compensatory growth is achieved. This shows that the mTOR pathway can affect the growth rate of abalone through nutritional regulation. In terms of energy metabolism, AMPK is a sensor of the energy state of cells, activated when energy is insufficient to inhibit synthesis and promote decomposition. Abalone is upregulated under stress such as hypoxia or hunger, thereby reducing growth-related energy consumption processes, which are manifested as growth stagnation. When the environment improves, the AMPK signal weakens and growth returns to normal. 5.2 Molecular networks that regulate immunity and stress resistance (such as NF-κB, HSP) When abalone faces pathogenic and environmental stress, it activates a complex immune and anti-resistance molecular network, with the NF-κB signaling pathway and the heat shock protein (HSP) system being two key modules. NF-κB is the core transcription factor of the innate immune response, which can sense stimulation of bacterial lipopolysaccharides and induce downstream antibacterial gene expression. In abalone, multiple NF-κB pathway elements have been cloned, such as receptor TLR, adapter MyD88, IκB and NF-κB subunits. Studies have shown that the TLR/NF-κB pathway of abalone is rapidly activated in the face of pathogen infection, promoting the expression of immune effector molecules such as tumor necrosis factor and lysozyme, thereby improving the anti-infection ability of abalone. However, under environmental stress such as continuous high temperature or low oxygen, the NF-κB pathway response is blocked, and the expression of immune genes decreases, resulting in immunosuppression. The heat shock protein (HSP) family is another important molecular system for abalone to resist environmental stress. HSP includes molecular chaperones such as HSP70 and HSP90, which are highly expressed under stress such as heat stress and heavy metals, helping cells fold damaged proteins and prevent aggregation. When abalone is stimulated by high temperature, mRNA and protein levels of HSP genes (such as HSP70, HSP90) increase sharply (Yasa et al., 2020). Mediated by HSP, abalone cells tolerate higher temperatures and recover quickly after stress is relieved. It is worth noting that HSP expression itself is regulated by the heat shock transcription factor HSF1 (Zhang et al., 2020). In breeding practice, screening and retaining individuals with strong HSP response under heat stress is expected to cultivate high-temperature resistant strains. 5.3 Gene regulation mechanisms involved in reproductive regulation The reproduction process of abalone is also finely regulated by genes and molecular pathways, including gonad development and maturation, gamete production and egg-laying behavior. The study found that multiple hormones and signaling factors are involved in this process. At the endocrine level, steroid hormones such as progesterone and estradiol may play a role in abalone gonad maturation, and their synthesis and effects involve a range of enzyme and receptor genes. At the same time, some neuropeptides and their receptors are upregulated in neural tissue during the abalone reproductive season, which is supposed to be a pro-reproductive signal. For example, GnRH-like peptides and dopamine may affect abalone gonad development and egg-laying behavior through the neuro-endocrine pathway. In addition to the hormone pathway, several specific genes have been shown to be closely related to the abalone reproductive process. IGF signal not only regulates growth, but also affects the
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