Fig. 7: Pol Ⅱ-CTD physically interacts with factors involved in alternative polyadenylation(APA).

a ChIP-qPCR analysis of Pol Ⅱ-CTD-S2P protein enrichment in the different sites of the SPX5 5′UTR region, upstream (1) or downstream (2) of the Poly(A) site, in WT and nat_spx5 mutant plants under P+/P—conditions. Data are presented as the mean ± SD, with n = 3 biologically independent replicates. Statistical significance was assessed using a two-sided unpaired Student’s t-test. **P <  0.01. b Examination of protein interactions between Pol Ⅱ-CTD/Pol Ⅱ-CTD^17A with SlCPSF30 or SlHLP1 by split luciferase complementation assays in tobacco leaves. Luciferase activities were detected 48 h after infiltration. c BiFC analysis for in vivo interaction between Pol Ⅱ-CTD/Pol Ⅱ-CTD^17A with SlCPSF30 or SlHLP1. The N-terminal fragment of GFP (nGFP) was fused to Pol Ⅱ-CTD/Pol Ⅱ-CTD^17A while the C-terminal fragment of GFP (cGFP) was fused to SlCPSF30 or SlHLP1. Scale bars = 20 µM. d Co-immunoprecipitation (Co-IP) assay for the interaction between Pol Ⅱ-CTD, and Pol Ⅱ-CTD^17A with SlCPSF30 or SlHLP1. Source data are provided as a Source Data file. e Model for the regulation of SlSPX5 expression by the Pi starvation inducible antisense transcript NAT_SPX5.