A tRNA epitranscriptomic checkpoint coordinates sperm mitochondrial load with embryonic allophagic clearance

The strict maternal inheritance of mitochondrial DNA is enforced by the efficient elimination of paternal mitochondria, yet the role of epigenetic regulation in this process remains unclear. In our recent study, we identify the demethylase ALKB‑1 as an essential factor for paternal mitochondrial elimination (PME) in Caenorhabditis elegans (C. elegans), functioning through tRNA m¹A demethylation. ALKB‑1 deficiency leads to tRNA hypermethylation, which disrupts mitochondrial proteostasis and increases ROS production, thereby activating SKN‑1-ATFS‑1 stress signaling. This cascade compromises mitochondrial reduction during spermatogenesis, resulting in an increased burden of paternal mitochondria transmitted to the embryo. Concurrently, ALKB‑1 is required in the embryo to sustain autophagic clearance, evidenced by impaired autophagic flux and delayed PME upon maternal loss. Thus, delayed clearance stems dually from an excessive mitochondrial load in sperm and a compromised autophagic degradation capacity in the embryo. Our work establishes ALKB‑1‑dependent tRNA demethylation as a dual‑germline epitranscriptomic checkpoint that ensures intergenerational mitochondrial quality control.