MS1/MMD1 homologues in the moss Physcomitrium patens are required for male and female gametogenesis.

The Arabidopsis Plant HomeoDomain (PHD) proteins AtMS1 and AtMMD1 provide chromatin-mediated transcriptional regulation essential for tapetum-dependent pollen formation. This pollen-based male gametogenesis is a derived trait of seed plants. Male gametogenesis in the common ancestors of land plants is instead likely to have been reminiscent of that in extant bryophytes where flagellated sperms are produced by an elaborate gametophyte generation.

PIF-independent regulation of growth by an evening complex in the liverwort Marchantia polymorpha.

Previous studies in the liverwort Marchantia polymorpha have shown that the putative evening complex (EC) genes LUX ARRHYTHMO (LUX) and ELF4-LIKE (EFL) have a function in the liverwort circadian clock. Here, we studied the growth phenotypes of MpLUX and MpEFL loss-of-function mutants, to establish if PHYTOCHROME-INTERACTING FACTOR (PIF) and auxin act downstream of the M. polymorpha EC in a growth-related pathway similar to the one described for the flowering plant Arabidopsis.

Dependence on clade II bHLH transcription factors for nursing of haploid products by tapetal-like cells is conserved between moss sporangia and angiosperm anthers.

Clade II basic helix-loop-helix transcription factors (bHLH TFs) are essential for pollen production and tapetal nursing functions in angiosperm anthers. As pollen has been suggested to be related to bryophyte spores by descent, we characterized two Physcomitrium (Physcomitrella) patens clade II bHLH TFs (PpbHLH092 and PpbHLH098), to test if regulation of sporogenous cells and the nursing cells surrounding them is conserved between angiosperm anthers and bryophyte sporangia. We made CRISPR-Cas9 reporter and loss-of-function lines to address the function of PpbHLH092/098.

The Physcomitrium patens egg cell expresses several distinct epigenetic components and utilizes homologues of BONOBO genes for cell specification.

Although land plant germ cells have received much attention, knowledge about their specification is still limited. We thus identified transcripts enriched in egg cells of the bryophyte model species Physcomitrium patens, compared the results with angiosperm egg cells, and selected important candidate genes for functional analysis. We used laser-assisted microdissection to perform a cell-type-specific transcriptome analysis on egg cells for comparison with available expression profiles of vegetative tissues and male reproductive organs.

Different Families of Retrotransposons and DNA Transposons Are Actively Transcribed and May Have Transposed Recently in () .

Similarly to other plant genomes of similar size, more than half of the genome of is covered by Transposable Elements (TEs). However, the composition and distribution of TEs is quite peculiar, with Long Terminal Repeat (LTR)-retrotransposons, which form patches of TE-rich regions interleaved with gene-rich regions, accounting for the vast majority of the TE space. We have already shown that RLG1, the most abundant TE in , is expressed in non-stressed protonema tissue.

Autophagy is required for gamete differentiation in the moss Physcomitrella patens.

Autophagy, a major catabolic process in eukaryotes, was initially related to cell tolerance to nutrient depletion. In plants autophagy has also been widely related to tolerance to biotic and abiotic stresses (through the induction or repression of programmed cell death, PCD) as well as to promotion of developmentally regulated PCD, starch degradation or caloric restriction important for life span. Much less is known regarding its role in plant cell differentiation.