Variations in endopolyploidy level during the short period of the early growing stage in the roots and leaves of maize (Zea mays) seedlings

Abstract

We used a flow cytometer to investigate the variations in endopolyploidy (the frequencies of nuclei with DNA contents equivalent to 4C through 16C) during the short period of the early growing stage in vigorously growing young tissues of maize seedlings. We examined different portions of the root and leaves that had been growing for 7 (day 7) and 13 (day 13) days after germination. Endoreplication showed two opposing phenomena without aging. In one case, the endopolyploidy of the first leaf was higher on day 13 than on day 7. In the latter case, endopolyploidy decreased, as clearly revealed by a comparison of the endopolyploidy of the second leaves and the 160-170 mm portion of the seminal root on days 7 and 13. Endopolyploidy was also lower in the top of the leaf. In roots, endopolyploidy was increased by the exogenous application of abscisic acid for only 1 day. The levels of endopolyploidy increased without an increase in cell size in the roots. These results showed that endoreplication occurs in actively growing and young tissue and that the variation can be induced in the short period examined.

Cyclin-dependent kinase complexes in developing maize endosperm: evidence for differential expression and functional specialization

“…Reduced 26S proteasome-mediated proteolysis of A-, B- and D-type cyclins could contribute to endoreduplication and the concomitant cell expansion in maize endosperm. In agreement with our results, cell expansion and post-mitotic stabilization of CYCA1;1, CYCB1;1 and CYCB2;1 (Mews et al 1997 , 2000 ) and endoreduplication (Ogawa et al 2010 ) all occur in the elongation zone of the maize root, further suggesting a link between reduced proteolysis of certain cyclins, cell expansion and endoreduplication. In support of this view, partial reduction of 26S proteasome activity in Arabidopsis leads to cell enlargement and increased endoreduplication in aerial organs (Kurepa et al 2009 ; Sonoda et al 2009 ).…”