Molecular cytogenetic analysis of polyploidization in the anther tapetum of diploid and autotetraploid Arabidopsis thaliana plants

Like those of most angiosperms, vegetative tissues of Arabidopsis thaliana undergo high levels of endopolyploidization. One such tissue is the anther tapetum which plays a role in male sporo- and gametogenesis. The degree of polyploidization of the tapetum varies from species to species. Although th e role of this process is not yet fully understood, it may be linked to fun ctioning of the tapetum, increasing the copy number of genes needed for the synthesis of specific factors required by developing pollen mother cells ( PMCs) and pollen grains. The present study focused on polyploidization duri ng the development of the tapetum of Arabidopsis thaliana. The aim was to o utline the mode of tapetum polyploidization in this model plant species and to establish an efficient method for analysing ploidy levels in differenti ated cells. The course and degree of tapetum polyploidization in Arabidopsi s was analysed in interphase nuclei using fluorescence in situ hybridizatio n (FISH) with repetitive DNA (45S rDNA). The stages of development of the t apetum were analysed alongside meiosis in PMCs. The majority of tapetal cel ls undergo two, maximally three, rounds of divisions. Tapetal nuclei have u sually divided by metaphase I of meiosis of PMCs. The pattern of tapetum po lyploidization was similar in diploid and autotetraploid plants and is thus not affected by increasing amounts of maternal plant DNA. The tapetum of a utotetraploid plants exhibits a higher frequency of additional division tha n seen in diploid plants. (C) 2001 Annals of Botany Company.