INCREASED LEVEL OF POLYPLOIDY 1(ILP1) encodes a novel transcriptional repressor that controls endoreduplication level in Arabidopsis.

Abstract

In plants most organs are composed of cells of various ploidy levels and endoreduplication is a key process in the plant's developmental plan.
We have isolated ilp1-D as a dominant mutant in which polyploidy level is increased both in light-grown cotyledons and dark-grown hypocotyls. ilp1-D showed correlation between increased cell volume with polyploidy.
ILP1 gene encodes for a novel nuclear protein homologous to the mammalian protein. We demonstrate that this protein functions as a transcriptional repressor in vivo.
T-DNA insertion mutants of ILP1 showed almost opposite phenotypes to ilp1-D, including decreased polyploidy level and small cell volume.
The expression of all the member of CYCA2 family was reduced in an ILP1 over-expressing line. This indicates that ILP1 is a repressor that control CYCA2 expression. T-DNA insertion mutants of CYCA2;1 has increased ploidy level. Here we demonstrate that ILP1 regulates endoreduplication through control of CYCA2 expression in Arabidopsis.