Pea has two variants of the CenH3 that fully colocalize in centromeres of all chromosomes.
A: Alignment of protein sequences of the pea CenH3 histones. Red line above the alignment marks a putative centromere targeting domain (CATD). Dotted lines above and below the alignment show the peptide sequences which were used as antigens to produce antibody to CenH3-1 and CenH3-2, respectively. Secondary structure of the histone fold domain is depicted below the alignment. B–C: Direct visualization of fusion proteins of CenH3-1 or CenH3-2 with YFP revealed 14 foci in the interphase nucleus, corresponding to the number of chromosomes in diploid cells. D: Fusion protein of canonical H3 with YFP is localized in whole nucleus. ELISA assays of the two CenH3 antibodies revealed low level of cross-reaction of the CenH3-1 antibody to the peptide designed from the CenH3-2 (data not shown). As we could not determine if the cross-reactivity was sufficient to produce signal after detection in situ, the colocalization experiments were performed using highly-specific antibodies to YFP and CenH3-2 in hairy root lines expressing CenH3-1_YFP. E–J: Detection of CenH3-1_YFP (red) and CenH3-2 (green) revealed full colocalization of the two proteins both in interphase nucleus (E–G) and metaphase chromosomes (H–J). K–M: Fully overlapping signals were observed also using simultaneous detection of CenH3 proteins with antibodies to CenH3-1 (red) and CenH3-2 (green) as shown on the example of chromosome 3 possessing three distinct domains containing CenH3. This indicates that either of the two antibodies was capable of detecting all functional centromere domains and that the gaps between individual domains lack CenH3 of any type. Bar = 5 µm.