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 ilp1-1D as a dominant mutant in which polyploidy level is increased in the seedlings. ilp1-1D showed correlation between increased cell volume with polyploidy. ILP1 gene encodes for a novel nuclear protein and this protein functions as a transcriptional repressor in vivo.
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.
ILP1 has homologs not only in plants but also in insects and mammals, and the mouse ortholog of the ILP1 also repressed cyclin A expression in mouse NIH3T3 cells.