Arabidopsis MDN1 Is Involved in the Establishment of a Normal Seed Proteome and Seed Germination

Abstract

Seed germination and formation are the beginning and ending, respectively, of a plant life cycle. These two processes are under fine regulation by the internal genetic information. Previously, we demonstrated that <i>Arabidopsis</i> MIDASIN 1 (MDN1) is required for ribosome biogenesis, and its dysfunction leads to pleiotropic developmental phenotypes, including impaired embryogenesis and slow seed germination. In this study, we further found that the weak mutant of <i>MDN1</i>, <i>mdn1-1</i>, exhibits an increased seed size phenotype. Seed proteomic analysis reveals that a number of proteins involved in seed development and response to external environments are mis-regulated by the MDN1 dysfunction. Many 2S seed storage proteins (SSPs) and late embryogenesis abundant (LEA) proteins are over-accumulated in the dry seeds of <i>mdn1-1</i>. Further, some genes encoding seed storage reserves are also upregulated in <i>mdn1-1</i> seedlings. More interestingly, abscisic acid-insensitive 5 (ABI5) is over-accumulated in <i>mdn1-1</i> seeds, and the loss of its function partially rescues the low seed germination rate of <i>mdn1-1</i>. Together, this study further demonstrates that MDN1 is essential for establishing a normal seed proteome, and its mutation triggers ABI5-mediated repression of seed germination.