NtDHS regulates leaf senescence by modulating gene translation in Nicotiana tabacum

The biochemical and transcriptional regulatory mechanisms of chlorophyll metabolism have been extensively studied, but the translational regulatory mechanisms remain poorly understood. In this study, we found that NtDHS1 deficiency in N. tabacum resulted in smaller leaves and increased leaf chlorophyll content. Protein content determination experiments revealed that the global protein synthesis of the Ntdhs1 mutant was decreased. A ribosome profiling sequence (Ribo-seq) assay showed that the translation level of genes related to cell growth was significantly reduced, while the translation level of chlorophyll metabolism related genes was significantly increased in Ntdhs1 mutant. Biochemical analysis further demonstrated that NtDHS interacts with the translation initiation factor NteIF5A. Moreover, the Nteif5a1 mutant exhibited phenotypes similar to the Ntdhs1 mutant, including a reduced translation level of cell growth related genes and increased translation level of chlorophyll metabolism related genes. Our studies suggest that the NtDHS–NteIF5A complex regulates leaf senescence by modulating the translation of specific genes.