Clathrin Light Chain 2 is a Substrate of Ubiquitin Ligase ATL5 and Negatively Regulates Seed Longevity in Arabidopsis.

Abstract

Seed longevity is crucial for both ecological and agronomical value. Previously, we demonstrated that the E3 ligase Arabidopsis tóxicos en levadura 5 (ATL5) positively regulates seed longevity by mediating the degradation of the activator of basal transcription 1 in Arabidopsis. In the present study, we demonstrated that clathrin light chain 2 (CLC2), another ubiquitinated substrate of ATL5, affects seed longevity in Arabidopsis. The interaction between CLC2 and ATL5 was first identified in yeast cells and then in planta. Seeds of clc2 mutants displayed slower accelerated aging, whereas CLC2-OE seeds showed faster accelerated aging than wild-type seeds. In vitro assay showed that ATL5 promotes CLC2 degradation through the 26S proteasome pathway. Degradation of endogenous CLC2 was diminished in atl5 seeds, which could be induced by aging and occurs in a proteasome-dependent manner. Moreover, the role of CLC2 in seed longevity was independent of endocytosis; however, CLC2 exhibited transcriptional activation activity. Transcriptomic analysis revealed that the expression of numerous ribosomal protein genes was significantly upregulated in clc2 seeds after aging. Collectively, our study demonstrated that CLC2 is another ubiquitinated substrate of ATL5 that negatively regulates seed longevity by influencing the expression of ribosomal protein genes in Arabidopsis.