Gametophytic epigenetic regulators MEDEA and DEMETER synergistically suppress ectopic shoot formation in Arabidopsis

Abstract

AbstractThe gametophyte to sporophyte transition facilitates the alternation of generations in a plant life cycle. The epigenetic regulators DEMETER(DME) and MEDEA(MEA) synergistically control central cell proliferation and differentiation, ensuring proper gametophyte to sporo-phyte transition inArabidopsis. Mutant alleles ofDMEandMEAare female gametophyte lethal, eluding the recovery of recessive homozygotes to examine their role in the sporophyte. Here, we exploited the paternal transmission of these mutant alleles coupled with CENH3-haploid inducer to generatemea-1;dme-2 sporophytes. Strikingly, the simultaneous loss of function of MEA and DME leads to the emergence of ectopic shoot meristems at the apical pole of the plant body axis.DMEandMEAare expressed in the developing shoot apex and regulate the expression of various shoot-promoting factors. Chromatin immunoprecipitation(ChIP), DNA methylation and gene expression analysis revealed several shoot regulators as potential targets of MEA and DME. Knockdown of upregulated shoot-promoting factors STM, CUC2, and PLT5 rescued the ectopic shoot phenotypes. Our findings reveal a previously unrecognized synergistic role of MEA and DME in restricting the meristematic activity at the shoot apex during sporophytic development to orchestrate the plant architecture.