Plant Cell Monogr (9)
D.P.S. Verma and Z. Hong: Cell Division Control in Plants
DOI 10.1007/7089_2007_123/Published online: 17 August 2007
©Springer-Verlag Berlin Heidelberg 2007
The Endoreduplication Cell Cycle: Regulation and Function
PaoloA.Sabelli·BrianA.Larkins()
Department of Plant Sciences, University of Arizona, P.O. Box 210036,
Tucson, AZ 85721, USA
[email protected]
AbstractThe endoreduplication cell cycle is a variant of the standard mitotic cell cycle
in which reiterated rounds of DNA synthesis occur in the absence of chromosome segre-
gation and cell division. The resulting polyploid cells are frequently found in plants and
often occur in tissues with a high metabolic activity that accumulate storage molecules. In
this chapter we review the current understanding of the regulatory mechanisms involved
in the modification of the mitotic cell cycle, based on a generally accepted template for
plant cell cycle control, that bring about endoreduplication, as well as the influence of
phytohormones and epigenetic factors. The regulation of endoreduplication is described
in two model systems: the developing maize endosperm and the leaf trichome ofAra-
bidopsis. In addition, we discuss the biological relevance and several proposed functions
of this specialized cell cycle.
1
Introduction
Endoreduplication is a form of somatic nuclear polyploidization in which
complete rounds of DNA synthesis occur in the absence of chromatin con-
densation, nuclear membrane breakdown, mitotic spindle formation, sister
chromatid segregation, and cytokinesis (Edgar and Orr-Weaver 2001; Larkins
et al. 2001). Because sister chromatids do not fully separate, endoredupli-
cated chromosomes are often larger and thicker than normal and are called
polytenic (Carvalheira 2000). Endoreduplication is the most common and
best characterized type of cell cycle variant leading to polyploidization.
However, several other cell cycle types, such as endomitosis, result in poly-
ploid cells and, sometimes, the distinction between them is not clear-cut
(Edgar and Orr-Weaver 2001). Endoreduplication is widespread in plants; it
has been estimated that it occurs in up to 90 %ofallangiospermspecies
(D’Amato 1984). InArabidopsis, with the exception of the inflorescence,
virtually all tissues and organs contain endoreduplicated cells (Galbraith
et al. 1983), although, importantly, not all cells in a given tissue may be
endoreduplicated or have undergone endoreduplication to the same extent.
Cells and tissues that have been found to be endoreduplicated in plants
include the seed endosperm (Larkins et al. 2001), antipodal and synergid
cells of the female gametophyte, embryo suspensor, cotyledons, anther hairs
and tapetum (D’Amato 1984), leaf trichomes (Schnittger and Hulskamp