3.5.6 Immune function
Genes and functional categories involved in the three stages of the innate immune response (sensing, signalling and effectors), were affected by CO2 treatment in both tissues (Table 5). In the eyes, the immune sensor molecule pglyrp2 was downregulated, while there was small, coordinated upregulation of genes belonging to the functional category ‘scavenger receptor activity’ which binds pathogens. Genes that mediate the immune response via cellular signalling pathways were DE, including upregulation of map4k5/3and syvn1-b, and downregulation of psenen in the CNS. In the eyes, there was upregulation of maoa, which plays a key role, via norepinephrine signalling, in the molluscan neuroendocrine-immune axis-like pathway (Liu et al., 2018; Sun et al., 2021; Zhou et al., 2011). Genes involved in the activation and production of immune effectors were also affected by COtreatment. In particular, tf coding for transferrin, which sequesters iron so it is unavailable for pathogens and is a key component of the molluscan innate immune response, including in squid (Herath et al., 2015; Lambert et al., 2005; Li et al., 2019; Ong et al., 2006; Salazar et al., 2015), was upregulated and positively correlated with CO2 treatment and activity traits in the CNS. The key molecular marker of autophagy, map1l3ca/b, which plays an important role in the molluscan immune response (Han et al., 2019; Moreau et al., 2015; Picot et al., 2019) was downregulated in the CNS. There was also small, coordinated upregulation of genes belonging to functional categories involved in mediating phagocytosis, including ‘cell adhesion’ and ‘integrin complex’. Genes involved in cell adhesion as part of the immune response (itga4, itga9, rac1, ptpr) were also positively correlated with CO2 treatment and activity traits. The cytoskeleton is also important for phagocytosis and there was small, coordinated upregulation of genes in three cytoskeleton-related functional categories in the CNS (‘motor activity’, ‘actin binding’, and ‘microtubule cytoskeleton’), and two downregulated in the eyes (‘cytoskeleton’ and ‘intermediate filament cytoskeleton organisation’) (Figure 4).