Protein Repair L-Isoaspartyl Methyltransferase1 Is Involved in Both Seed Longevity and Germination Vigor in Arabidopsis

摘要

The formation of abnormal amino acid residues is a major source of spontaneous age-related protein damage in cells. Thenprotein L-isoaspartyl methyltransferase (PIMT) combats protein misfolding resulting from L-isoaspartyl formation byncatalyzing the conversion of abnormal L-isoaspartyl residues to their normal L-aspartyl forms. In this way, the PIMT repairnenzyme system contributes to longevity and survival in bacterial and animal kingdoms. Despite the discovery of PIMTnactivity in plants two decades ago, the role of this enzyme during plant stress adaptation and in seed longevity remainsnundefined. In this work, we have isolated Arabidopsis thaliana lines exhibiting altered expression of PIMT1, one of the twongenes encoding the PIMT enzyme in Arabidopsis. PIMT1 overaccumulation reduced the accumulation of L-isoaspartylnresidues in seed proteins and increased both seed longevity and germination vigor. Conversely, reduced PIMT1 accumulationnwas associated with an increase in the accumulation of L-isoaspartyl residues in the proteome of freshly harvestedndry mature seeds, thus leading to heightened sensitivity to aging treatments and loss of seed vigor under stressfulngermination conditions. These data implicate PIMT1 as a major endogenous factor that limits abnormal L-isoaspartylnaccumulation in seed proteins, thereby improving seed traits such as longevity and vigor. The PIMT repair pathway likelynworks in concert with other anti-aging pathways to actively eliminate deleterious protein products, thus enabling successfulnseedling establishment and strengthening plant proliferation in natural environments.