Maize root responds to nitrate by modulating its development through the coordinated action of many interacting players. Nitric oxide is produced in primary root early after the nitrate provision, thus inducing root elongation. In this study, RNA sequencing was applied to discover the main molecular signatures distinguishing the response of maize root to nitrate according to their dependency on, or independency of, nitric oxide, thus discriminating the signaling pathways regulated by nitrate through nitric oxide from those regulated by nitrate itself of by further downstream factors. A set of subsequent detailed functional annotation tools (Gene Ontology enrichment, MapMan, KEGG reconstruction pathway, transcription factors detection) were used to gain further information and the lateral root density was measured both in the presence of nitrate and in the presence of nitrate plus cPTIO, a specific NO scavenger, and compared to that observed for N-depleted roots. Our results led us to identify six clusters of transcripts according to their responsiveness to nitric oxide and to their regulation by nitrate provision. In general, shared and specific features for the six clusters were identified, allowing us to determine the overall root response to nitrate according to its dependency on nitric oxide.

CYP1B1 is a key enzyme involved in xenobiotic and endogenous metabolism, yet its physiological role in bovine liver homeostasis remains unclear. In this study, we generated a CYP1B1 knockout (CYP1B1^KO) bovine hepatocyte-like cell line to indirectly investigate its role in liver function. Transcriptomic analysis revealed alterations in immune regulation, epithelial barrier integrity, and detoxification pathways, with concurrent compensatory CYP1A1 upregulation. Beyond its physiological role, CYP1B1 was found to actively participate in Aflatoxin B1 (AFB1) metabolism, a mycotoxin posing significant health risks to humans and livestock. Molecular docking suggested that CYP1B1 facilitates the conversion of AFB1 into AFM1 and AFBO. In agreement with these predictions, CYP1B1^KO cells exposed to AFB1 showed reduced AFM1 production and decreased cytotoxicity. Further transcriptomic analysis indicated that CYP1B1^KO cells exhibited mitigated oxidative stress and inflammatory responses, along with downregulation of CYP3A74, a key enzyme in AFB1 bioactivation. This suggests that CYP1B1 KO reduces AFB1 toxicity by directly limiting AFB1 bioactivation and indirectly modulating the broader hepatic CYP network, further limiting the formation of toxic intermediates. These findings provide novel insights into CYP1B1’s function in bovine hepatocytes, highlighting its dual role in maintaining liver homeostasis and mediating AFB1 metabolism. The observed interplay between CYP1B1, CYP1A1, and CYP3A74 underscores the complexity of AFB1 biotransformation and warrants further investigation into the coordinated regulation of xenobiotic metabolism in cattle.

Cytochrome P450 3A (CYP3A) enzymes catalyze the metabolism of a wide range of endogenous and exogenous compounds. Genetic variations in the 3 CYP3A isoforms (CYP3A28, CYP3A74, and CYP3A76) may influence their expression and activity, leading to inter-individual differences in xenobiotic metabolism. In domestic cattle, understanding how genetic variations modulate CYP3A activity is crucial for both its therapeutic implications (clinical efficacy and adverse drug effects) and food safety (residues in foodstuff). Here, we updated the variant calling of CYP3As in 300 previously sequenced Piedmontese beef cattle, using the most recent reference genome, which contains an updated, longer sequence for CYP3A28. All but one previously identified missense variants were confirmed and a new variant, R105W in CYP3A28, was discovered. Through computational mutagenesis and molecular docking, we computationally predicted the impact of all identified CYP3A variant enzymes on protein stability and their affinity for aflatoxin B1 (AFB1), a potent carcinogen and food contaminant. For CYP3A28, we also computationally predicted its affinity for the probe substrate nifedipine (NIF). We found that CYP3A28 with R105W variant cannot accommodate NIF nor AFB1 in the binding pocket, thus affecting their metabolism. Our work provides computational foundation and prioritized ranking of CYP3A variants for future experimental validations.