Neural stem cells alter nucleocytoplasmic partitioning and accumulate nuclear polyadenylated transcripts during quiescence

Quiescence is a cellular state characterised by reversible cell-cycle arrest and diminished biosynthetic activity that protects against environmental insults, replicative exhaustion and proliferation-induced mutations1. Entry into and exit from this state controls development, maintenance and repair of tissues plus, in the adult central nervous system, generation of new neurons and thus cognition and mood2-4. Cancer stem cells too can undergo quiescence, which confers them resistance to current therapies5,6. Despite clinical relevance, quiescence is poorly understood and is defined functionally given lack of molecular markers. Decrease of the most resource-intensive cellular process of protein synthesis is a feature of quiescence, controlled across species and cell types by inhibition of the Target of Rapamycin pathway1,7. Here, we combine Drosophila genetics and a mammalian model to show that altered nucleocytoplasmic partitioning and nuclear accumulation of polyadenylated RNAs are novel evolutionarily conserved hallmarks of quiescence regulation. These mechanisms provide a previously unappreciated regulatory layer to reducing protein synthesis in quiescent cells, whilst priming them for reactivation in response to appropriate cues.

Generated land systems: recognition and prospects of land system science

Although land system research has made important progress in land change monitoring, long-term histories of land use change, land system change modeling, and case-study synthesis, it still faces some challenges in system integration and comprehensive analysis. To better understand and explore the comprehensiveness of land systems, system integration theory should be combined with system generation theory that emphasizes historical accumulation. Therefore, this paper revisits some of the basic connotations and theories of land system science by reviewing relevant research and proposes the concept of generated land systems based on system generation theory with an aim to providing a reference base for future research. As coupled human–environment systems are generated by mankind’s transformation, utilization, and adaptation of the land surface and its upper and lower spaces of Earth, generated land systems evolve in the mutual generation and restriction of the biophysical environment, land use, and social economy. The evolution forms of generated land systems can be classified as fluctuation, degradation, and optimization based on the ascendency and resilience of the system. The need for generated land systems to be multi-functional is what motivates the direction and form of generated land system evolution. Generation mechanism, process, adaptability, scale effect, and tele-coupling are important issues of generated land system research. In addition, how generated land systems can enter a new evolutionary cycle through functional transformation is also crucial to achieving sustainable management and utilization of land resources.