Identification of an Arabidopsis thaliana gene encoding a plasma membrane H(+)-ATPase whose expression is restricted to anther tissue

A gene (aha9) for a plasma membrane H(+)-ATPase was isolated from an Arabidopsis thaliana genomic library and sequenced. Comparison of the aha9 predicted amino acid sequence with those of aha1, 2 and 3 and analogous genes from other species indicated the existence of at least two aha gene subfamilies whose divergence precedes that of the Nicotiana and Arabidopsis species. Transcript analysis in various organs revealed expression of aha9 in flower tissues only. Introduction of aha9 into Nicotiana tabacum by genetic transformation gave rise to transgenic plants which also express aha9 in flower tissues. A more detailed analysis showed that aha9 expression was restricted to anther tissues

Arabidopsis MZT1 homologs GIP1 and GIP2 are essential for centromere architecture

Centromeres play a pivotal role in maintaining genome integrity by facilitating the recruitment of kinetochore and sister-chromatid cohesion proteins, both required for correct chromosome segregation. Centromeres are epigenetically specified by the presence of the histone H3 variant (CENH3). In this study, we investigate the role of the highly conserved gamma-tubulin complex protein 3-interacting proteins (GIPs) in Arabidopsis centromere regulation. We show that GIPs form a complex with CENH3 in cycling cells. GIP depletion in the gip1gip2 knockdown mutant leads to a decreased CENH3 level at centromeres, despite a higher level of Mis18BP1/KNL2 present at both centromeric and ectopic sites. We thus postulate that GIPs are required to ensure CENH3 deposition and/or maintenance at centromeres. In addition, the recruitment at the centromere of other proteins such as the CENP-C kinetochore component and the cohesin subunit SMC3 is impaired in gip1gip2. These defects in centromere architecture result in aneuploidy due to severely altered centromeric cohesion. Altogether, we ascribe a central function to GIPs for the proper recruitment and/or stabilization of centromeric proteins essential in the specification of the centromere identity, as well as for centromeric cohesion in somatic cells