The interaction between the receptor-like kinase (RLK) FERONIA (FER) and the secreted peptide Rapid Alkalinization Factor 1 (RALF1) is vital for development and stress responses in Arabidopsis. Ligand-induced membrane dynamics affect the function of several RLKs, but the effects of the RALF1-FER interaction on the dynamics of FER and the ensuing effects on its functionality are poorly understood. Here, we show that RALF1 modulated the dynamics and partitioning of FER-GFP at the plasma membrane (PM). Moreover, FER was internalized by both clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE) under steady state conditions. After RALF1 treatment, FER-GFP internalization was primarily enhanced via the CME pathway, raising FER-GFP levels in the vacuole. RALF1 treatment also modulated trafficking of other PM proteins such as PIN2-GFP and BRI1-GFP, increasing their vacuolar levels by enhancing their internalization. Importantly, blocking CME attenuated RALF1-mediated root growth inhibition independently of RALF1-induced early signaling, suggesting that the RALF1 can also exert its effects via the CME pathway. These findings reveal that the RALF1-FER interaction modulates plant growth and development and this may also involve endocytosis of PM proteins.

Plants, which are sessile unlike most animals, have evolved a system to reduce growth under stress; however, the molecular mechanisms of this stress response are not well known. During programmed development, a fraction of the leaf epidermal precursor cells become meristemoid mother cells (MMCs), which are stem cells that produce both stomatal guard cells and epidermal pavement cells. Here we report that Arabidopsis plants, in response to osmotic stress, post-transcriptionally decrease the protein level of SPEECHLESS, the transcription factor promoting MMC identity, through the action of a mitogen-activated protein kinase (MAPK) cascade. The growth reduction under osmotic stress was lessened by inhibition of the MAPK cascade or by a mutation that disrupted the MAPK target amino acids in SPEECHLESS, indicating that Arabidopsis reduces growth under stress by integrating the osmotic stress signal into the MAPK-SPEECHLESS core developmental pathway.

The positioning and density of leaf stomata are regulated by three secretory peptides, EPIDERMAL PATTERNING FACTOR 1 (EPF1), EPF2 and stomagen. Several lines of published evidence have suggested a regulatory pathway as follows. EPF1 and EPF2 are perceived by receptor complexes consisting of a receptor-like protein, TOO MANY MOUTHS (TMM), and receptor kinases, ERECTA (ER), ERECTA-LIKE (ERL) 1 and ERL2. These receptors activate a mitogen-activated protein (MAP) kinase module. MAP kinases phosphorylate and destabilize the transcription factor SPEECHLESS (SPCH), resulting in a decrease in the number of stomatal lineage cells. Stomagen acts antagonistically to EPF1 and EPF2. However, there is no direct evidence that EPF1 and EPF2 activate or that stomagen inactivates the MAP kinase cascade, through which they might regulate the SPCH level. Experimental modulation of these peptides in Arabidopsis thaliana would change the number of stomatal lineage cells in developing leaves, which in turn would change the expression of SPCH, making the interpretation difficult. Here we reconstructed this signaling pathway in differentiated leaf cells of Nicotiana benthamiana to examine signaling without the confounding effect of cell type change. We show that EPF1 and EPF2 are able to activate the MAP kinase MPK6, and that both EPF1 and EPF2 are able to decrease the SPCH level, whereas stomagen is able to increase it. Our data also suggest that EPF1 can be recognized by TMM together with any ER family receptor kinase, whereas EPF2 can be recognized by TMM together with ERL1 or ERL2, but not by TMM together with ER.

Background Tetracentron sinense is an endemic and endangered deciduous tree. It belongs to the Trochodendrales, one of four early diverging lineages of eudicots known for having vesselless secondary wood. Sequencing and resequencing of the T. sinense genome will help us understand eudicot evolution, the genetic basis of tracheary element development, and the genetic diversity of this relict species. Results Here, we report a chromosome-scale assembly of the T. sinense genome. We assemble the 1.07 Gb genome sequence into 24 chromosomes and annotate 32,690 protein-coding genes. Phylogenomic analyses verify that the Trochodendrales and core eudicots are sister lineages and showed that two whole-genome duplications occurred in the Trochodendrales approximately 82 and 59 million years ago. Synteny analyses suggest that the γ event, resulting in paleohexaploidy, may have only happened in core eudicots. Interestingly, we find that vessel elements are present in T. sinense, which has two orthologs of AtVND7, the master regulator of vessel formation. T. sinense also has several key genes regulated by or regulating TsVND7.2 and their regulatory relationship resembles that in Arabidopsis thaliana. Resequencing and population genomics reveals high levels of genetic diversity of T. sinense and identifies four refugia in China. Conclusions The T. sinense genome provides a unique reference for inferring the early evolution of eudicots and the mechanisms underlying vessel element formation. Population genomics analysis of T. sinense reveals its genetic diversity and geographic structure with implications for conservation.

Endodormancy and the related chilling requirement synchronize the seasonal development of trees from the boreal and temperate regions under the climatic conditions prevailing at their native growing sites. The phenomenon of endodormancy has been known at the whole-plant level for 100 years, and in the last couple of decades, insights into the physiological and molecular basis of endodormancy and its release have also been obtained. Intriguingly, recent studies have shown experimentally that subtropical trees also show endodormancy and a chilling requirement. Motivated by the climatic differences between the subtropical and more northern zones, here we address the similarities and differences in endodormancy between trees growing in the subtropical zone and those growing in more northern zones.