Endopolyploidy in Plants

Abstract

Endopolyploidy is a general term describing the multiplication of nuclear DNA within the cell. In plants, this takes place via several mechanisms but mainly through the process of endoreduplication. Endoreduplication involves the replication of chromosomal deoxyribonucleic acid (DNA) without intervening mitoses and no obvious chromatin condensation/decondensation, with chromatids staying united either at the centromere or rarely, along their entire length. The occurrence of this form of endopolyploidy is uneven across plants; thus far, it has not been detected in some lineages (e.g. liverworts), whereas it is common in angiosperms (flowering plants), where very high levels (up to 24 567C) of endopolyploidy have been reported in some tissues. Internal and external factors contribute to the mechanisms underlying endopolyploidy, which can be seen as a key part of the developmental flexibility of plants. Recent work has shown that endopolyploidy may also play an important role in the response of plants to environmental stress. Key Concepts The frequency of endopolyploidy varies across different lineages of land plants. Three types of endopolyploidy have been reported in plants – endocycles, endomitosis and progressive partial endoreduplication, of which the endocycle is the most common. Endopolyploidy can reach very high levels in some plant cells (up to 24 567C). Endopolyploidy can lead to an increase in cell size, especially when the number of endocycles is high. The switch from the mitotic cell cycle to the endocycle involves changes in the regulation and abundance of a variety of cyclin‐dependent kinases (CDKs), cyclins (CYC) and regulatory proteins/transcription factors. Endopolyploidy is common in reproductive tissues of plants, for example the nutritive tissue of the endosperm in seeds. The onset of endopolyploidy is induced in some cell tissues in response to stress.

Ploidy and Size at Multiple Scales in the Arabidopsis Sepal

“…Microscopy observations of endoreduplicated chromosomes in plants have been more limited, but full or partial polyteny has been described in suspensor and tapetum cells, xylem cells, and trichomes (Nagl, 1969;Carvalheira, 2000;Sugimoto-Shirasu and Roberts, 2003). Endoreduplicated plant chromosomes have been observed to be incompletely aligned or partially polytene, and the degree of chromatid synapsis tends to decrease as ploidy increases (Matzke et al, 2005;Schubert et al, 2006Schubert et al, , 2012Leitch and Dodsworth, 2017). The degree of polyteny can also be cell type specific: Analysis of fluorescent centromere markers suggested that endoreduplicated Arabidopsis root cells were completely polytene at the centromere, whereas chromosomes in endoreduplicated leaf pavement cells were more dissociated (Fang and Spector, 2005).…”

Diversity in genome size and GC content shows adaptive potential in orchids and is closely linked to partial endoreplication, plant life‐history traits and climatic conditions

“…() and Brown et al . (), respectively), cells only replicate specific parts of chromosomal DNA, resulting in nuclei with (substantially) a less than two‐fold increase in DNA content (Leitch & Dodsworth, ). This phenomenon has been identified in representatives of all orchid subfamilies except the Apostasioideae (Trávníček et al ., ) and exhibits clade‐specific, and therefore phylogenetically constrained, behaviour (Bateman et al ., ).…”

Do Specialized Cells Play a Major Role in Organic Xenobiotic Detoxification in Higher Plants?

“…In fact, Barkla et al. (2018) pointed out that “highly metabolically active cells appear to have the highest levels of endopolyploidy, as it has been demonstrated in the endosperm and suspensor cells of the seeds of Arum maculatum and Phaseolus coccineus (24,567 and 8,192C, respectively; Leitch and Dodsworth, 2017 )”. Despite a majority of tissues within Arabidopsis endoreduplicate at a basal level ( Buchanan et al., 2000 ), it is important to keep in mind that endopolyploidy-associated growth is sometimes confined to specialized cell types or tissues that perform specific biological functions ( e.g.…”