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

Abstract

The gametophyte to sporophyte transition is an important event facilitating the alternation of generations in a plant life cycle. The paternally imprinted epigenetic regulators DEMETER(DME) and MEDEA(MEA) synergistically control central cell proliferation and differentiation, ensuring proper gametophyte to sporophyte transition in Arabidopsis. Mutant alleles of DME and MEA are maternal 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 CENH3haploid inducer to generate mea-1;dme-2 sporophytes. Strikingly, the simultaneous loss of function of MEA and DME leads to the emergence of multiple shoot meristems at the apical pole of the plant body axis. DME and MEA are expressed in the developing shoot apex and regulate the expression of various shoot-promoting factors. Chromatin immunoprecipitation(ChIP) and DNA methylation analysis revealed several shoot regulators as potential targets of MEA and DME, with mea-1 -/-;dme-2 -/seedlings showcasing their misexpression. Knockdown of upregulated shootpromoting 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.