FGF8-mediated signaling regulates tooth developmental pace during odontogenesis

The developing human and mouse teeth constitute an ideal model system to study the regulatory mechanism underlying organ growth control since their teeth share highly conserved and well-characterized developmental processes, and their developmental tempo varies notably. In the current study, we manipulated heterogenous recombination between human and mouse dental tissues and demonstrated that the dental mesenchyme dominates the tooth developmental tempo and FGF8 could be a critical player during this developmental process. Forced activation of FGF8 signaling in the dental mesenchyme of mice promoted cell proliferation, prevented cell apoptosis via p38 and perhaps PI3 K-Akt intracellular signaling,and impelled the transition of the cell cycle from G1-to S-phase in the tooth germ, resulting in the slowdown of the tooth developmental pace. Our results provide compelling evidence that extrinsic signals can profoundly affect tooth developmental tempo, and the dental mesenchymal FGF8 could be a pivotal factor in controlling the developmental pace in a non-cell-autonomous manner during mammalian odontogenesis.

A Plant SMALL RNA-BINDING PROTEIN 1 Family Mediates Cell-to-Cell Trafficking of RNAi Signals

In plants,RNA interference(RNAi)plays a pivotal role in growth and development,and responses to environmental inputs,including pathogen attack.The intercellular and systemic trafficking of small interfering RNA(siRNA)/microRNA(miRNA)is a central component in this regulatory pathway.Currently,little is known with regards to the molecular agents involved in the movement of these si/miRNAs.To address this situation,we employed a biochemical approach to identify and characterize a conserved SMALL RNA-BINDING PROTEIN 1(SRBP1)family that mediates non-cell-autonomous small RNA(sRNA)trafficking.In Arabidopsis,AtSRBP1 is a glycine-rich(GR)RNA-binding protein,also known as AtGRP7,which we show binds single-stranded siRNA.A viral vector,Zucchini yellow mosaic virus(ZYMV),was employed to functionally characterized the AtSRBP1-4(AtGRP7/2/4/8)RNA recognition motif and GR domains.Cellular-based studies revealed the GR domain as being necessary and sufficient for SRBP1 cell-to-cell movement.Taken together,our findings provide a foundation for future research into the mechanism and function of mobile sRNA signaling agents in plants.

Patterning the embryo in higher plants:Emerging pathways and challenges

Embryogenesis,which establishes the basic body plan for the post-embryonic organs after stereotyped cell divisions,initiates the first step of the plant life cycle.Studies in the last two decades indicate that embryogenesis is a precisely controlled process,and any defect would result in abnormalities.Here we discuss the recent progresses,with a focus on the cellular pathways governing early embryogenesis in the model species Arabidopsis.