Deciphering the molecular logic of WOX5 function in the root stem cell organizer.

Plant and animal stem cells receive signals from their surrounding cells to stay undifferentiated. In the Arabidopsis root, the quiescent center (QC) acts as a stem cell organizer, signaling to the neighboring stem cells. WOX5 is a central transcription factor regulating QC function.

Obligate mutualistic cooperation limits evolvability.

Cooperative mutualisms are widespread and play fundamental roles in many ecosystems. Given that these interactions are often obligate, the Darwinian fitness of the participating individuals is not only determined by the information encoded in their own genomes, but also the traits and capabilities of their corresponding interaction partners. Thus, a major outstanding question is how obligate cooperative mutualisms affect the ability of organisms to adapt evolutionarily to changing environmental conditions.

A Molecular Framework for the Embryonic Initiation of Shoot Meristem Stem Cells.

The establishment of pluripotent stem cells is a key event during plant and animal embryogenesis, but the underlying mechanisms remain enigmatic. We show that in the flowering plant Arabidopsis thaliana, expression of the shoot meristem stem cell marker CLV3 becomes detectable in transition stage embryos. Surprisingly, the key regulator of stem cell homeostasis WUSCHEL (WUS) is expressed but dispensable for stem cell initiation.

Deletion of Proton Gradient Regulation 5 (PGR5) and PGR5-Like 1 (PGRL1) proteins promote sustainable light-driven hydrogen production in Chlamydomonas reinhardtii due to increased PSII activity under sulfur deprivation.

Continuous hydrogen photo-production under sulfur deprivation was studied in the Chlamydomonas reinhardtii pgr5 pgrl1 double mutant and respective single mutants. Under medium light conditions, the pgr5 exhibited the highest performance and produced about eight times more hydrogen than the wild type, making pgr5 one of the most efficient hydrogen producer reported so far. The pgr5 pgrl1 double mutant showed an increased hydrogen burst at the beginning of sulfur deprivation under high light conditions, but in this case the overall amount of hydrogen produced by pgr5 pgrl1 as well as pgr5 was diminished due to photo-inhibition and increased degradation of PSI.

Evolution in regulatory regions rapidly compensates the cost of nonoptimal codon usage.

The redundant genetic code contains synonymous codons, whose relative frequencies vary among species. Nonoptimal codon usage lowers gene translation efficiency, potentially leading to a fitness cost. This is particularly relevant for horizontal gene transfer, common among bacteria and a key player in antibiotic resistance propagation.

Differential expression of WOX genes mediates apical-basal axis formation in the Arabidopsis embryo.

Axis formation is one of the earliest patterning events in plant and animal embryogenesis. In Arabidopsis, the main axis of the embryo is evident at the asymmetric division of the zygote into a small, embryonic apical cell and a large extraembryonic basal cell. Here we show that the homeobox genes WOX2 and WOX8, which are initially coexpressed in the zygote, act as complementary cell fate regulators in the apical and basal lineage, respectively.

Lack of the small plastid-encoded PsbJ polypeptide results in a defective water-splitting apparatus of photosystem II, reduced photosystem I levels, and hypersensitivity to light.

Photosystem II is a large pigment-protein complex catalyzing water oxidation and initiating electron transfer processes across the thylakoid membrane. In addition to large protein subunits, many of which bind redox cofactors, photosystem II particles contain a number of low molecular weight polypeptides whose function is only poorly defined. Here we have investigated the function of one of the smallest polypeptides in photosystem II, PsbJ.