Plant mobile domain proteins ensure Microrchidia 1 expression to fulfill transposon silencing

Abstract

Silencing of transposable elements (TEs) is an essential process to maintain genomic integrity within the cell. InArabidopsis, together with canonical epigenetic pathways such as DNA methylation and modifications of histone tails, the plant mobile domain (PMD) proteins MAINTENANCE OF MERISTEMS (MAIN) and MAIN-LIKE 1 (MAIL1) are involved in TE silencing. In addition, the MICRORCHIDIA (MORC) ATPases, including MORC1, are important cellular factors repressing TEs. Here, we describe the genetic interaction and connection between the PMD and MORC pathways by showing thatMORC1expression is impaired inmainandmail1mutants. Transcriptomic analyses of higher order mutant plants combiningpmdandmorc1mutations, andpmdmutants in whichMORC1expression is restored, show that the silencing defects of a subset of TEs inpmdmutants are most likely the consequence ofMORC1down-regulation. Besides, a significant fraction of up-regulated TEs inpmdmutants are not targeted by the MORC1 pathway.