Abstract
Mediator is a large multiprotein complex that is required for the transcription of most, if not all, genes transcribed by RNA Polymerase II. A core set of subunits is essential to assemble a functional Mediator in vitro and, therefore, the corresponding loss-of-function mutants are expected to be lethal. The MED30 subunit is essential in animal systems, but is absent in yeast. Here, we report that MED30 is also essential for both male gametophyte and embryo development in the model plant Arabidopsis thaliana Mutant med30 pollen grains were viable and some were able to germinate and target the ovules, although the embryos aborted shortly after fertilization, suggesting that MED30 is important for the paternal control of early embryo development. When gametophyte defects were bypassed by specific pollen complementation, loss of MED30 led to early embryo development arrest. Later in plant development, MED30 promotes flowering through multiple signaling pathways; its downregulation led to a phase change delay, downregulation of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3 (SPL3), FLOWERING LOCUS T (FTI) and SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1), and upregulation of FLOWERING LOCUS C (FLC).
Highlights
Mediator is a large protein complex that is conserved in eukaryotes and has an essential role in RNA polymerase II (RNA pol II)mediated transcription
Arabidopsis med30 loss-of-function alleles are not transmitted through the male gametophyte To study the role of the MED30 subunit, we obtained two T-DNA lines from the SALK collection (Alonso et al, 2003), which we named med30-1 (SALK_094948) and med30-2 (SALK_117444)
MED30 was widely expressed in various tissues (Fig. S2), including pollen, embryos and seeds, suggesting that these reproductive stages would be affected by loss-of-function mutations in MED30
Summary
Mediator is a large protein complex that is conserved in eukaryotes and has an essential role in RNA polymerase II (RNA pol II)mediated transcription. Arabidopsis MED30 is essential for allele transmission through the male gametophyte, is essential for embryo and seed development and, later on, promotes phase transitions during subsequent developmental stages. Aborted ovules or embryos, fewer seeds and a higher number of abnormal siliques compared with wild-type plants (Fig. S3 and Table S1).
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