Functional roles of arabidopsis elongin A and C in UV stress tolerance and development

• Arabidopsis eloa and eloc mutants show enhanced UV sensitivity. • ELOA overexpression improves hypocotyl tolerance to UV stress. • YFP-ELOA is nuclear, while YFP-ELOC relocalizes after UV exposure. • ELOA and ELOC regulate seed yield and plant growth in Arabidopsis . Elongins A (ELOA), B (ELOB), and C (ELOC) were originally identified in mammals as transcription elongation complex. Beyond this role, the three mammalian elongins function in E3 ligase complex that degrades the large subunit of the stalled RNA polymerase II after DNA damage. S. cerevisiae lacks ELOB but posseses ELOA and ELOC homologs which form a similar E3 ligase complex that performs a comparable function in targeting stalled RNA polymerase II for degradation. These yeast homologs are functionally conserved with their mammalian counterparts, as yeast ELOC enhances mammalian ELOA transcript elongation via interacting with it. However, yeast ELOA/C complex alone does not promote yeast transcriptional elongation. Their role in RNA polymerase II polyubiquitylation and degradation following DNA damage has been well characterized. In this study, we identified Arabidopsis elongin A homologue (ELOA; At2g42780) and examined the roles of ELOA and elongin C homologue (ELOC; At5g59140) in UV tolerance and development using molecular and genetic analyses. YFP-ELOA localized to nucleus and this pattern was not affected after UV treatment. However, YFP-ELOC localized to both nuclei and cytosol with reduced cytoplasmic signal post-UV exposure. Both Ateloa-2 and Ateloc-3 mutants exhibited enhanced UV-sensitive phenotypes in seedlings and adults. ELOA overexpression enhanced hypocotyl UV tolerance. Yeast two-hybrid assay confirmed the interaction between Arabidopsis ELOA and ELOC. Interestingly, ELOA and ELOC overexpression increased silique length and seed number, and ELOC overexpression also increased plant height. These findings demonstrate that Arabidopsis ELOA and ELOC homologs are required for UV tolerance and contribute to plant developmental regulation.