To understand the sequence variation surrounding the PRO1, PRO2 and INT6 sites, we reanalysed available Arabidopsis genome sequences (The 1001 Genomes Consortium, 2016). Besides the PRO1 1 bp deletion, the region surrounding PRO1 was conserved and we therefore focussed on the PRO1T/- deletion polymorphism (Figure 4A). Few bases up- and downstream of PRO2 (bp −102 to bp −92), we detected four additional highly diverse SNPs and designated this region PRO2+. We also identified additional frequent haplotypes of the INT6 triplet (INT6+). Apart from the two PolyA motifs located at PRO2+ and INT6+, the four remaining PolyA motifs were conserved across all accessions examined (Figure 4B).