A systematic analysis of AOS genes in tobacco reveals the role of NtAOS7 in jasmonic acid biosynthesis and stress tolerance

Jasmonic acid (JA) is a critical phytohormone that mediates plant defense mechanisms against herbivores and pathogens. Within the JA biosynthesis pathway, allene oxide synthase (AOS), a rate-limiting enzyme, plays a pivotal role in plant responses to biotic and abiotic stresses. However, the specific involvement of AOS in Nicotiana tabacum (tobacco) during stress conditions has yet to be explored. In this study, we identified 12 AOS genes distributed across eight chromosomes in tobacco, encoding proteins that range from 300 to 550 amino acids and contain up to 12 conserved motifs. Cis-acting element analysis revealed the presence of elements responsive to light, stress, and hormones in the promoters of these genes. Quantitative RT-PCR analysis demonstrated that several NtAOS genes were responsive to a variety of abiotic and hormonal stresses, with NtAOS7 showing significant upregulation under both abiotic stress and methyl jasmonate (MeJA) treatment. To explore its functional role, NtAOS7 knockout and overexpression lines were generated via gene editing. Phenotypic analysis revealed that NtAOS7 knockout mutants exhibited increased plant height, whereas overexpression of NtAOS7 led to reduced plant height and delayed flowering. Hormonal profiling further demonstrated that JA levels were significantly reduced in the NtAOS7 knockout lines, while overexpression of NtAOS7 resulted in elevated JA levels, indicating that NtAOS7 plays an important role in endogenous JA biosynthesis. Stress tolerance assays showed that NtAOS7 enhances plant resistance to cold and salt stresses. This study provides novel insights into the role of AOS in tobacco, setting the stage for future research into its involvement in stress adaptation and hormone signaling. Our findings establish NtAOS7 as a key regulatory player in JA biosynthesis, coordinating plant growth, developmental timing, and abiotic stress tolerance in tobacco. These insights contribute to the broader understanding of JA’s role in plant adaptation and open avenues for future biotechnological applications aimed at improving stress resilience in crops.