A knowledge of intraspecific divergence and range dynamics of dominant forest trees in response to past geological and climate change is of major importance to an understanding of their recent evolution and demography. Such knowledge is informative of how forests were affected by environmental factors in the past and may provide pointers to their response to future environmental change. However, genetic signatures of such historical events are often weak at individual loci due to large effective population sizes and long generation times of forest trees. This problem can be overcome by analysing genetic variation across multiple loci. We used this approach to examine intraspecific divergence and past range dynamics in the conifer Picea likiangensis, a dominant tree of forests occurring in eastern and southern areas of the Qinghai-Tibet Plateau (QTP). We sequenced 13 nuclear loci, two mitochondrial DNA regions and three plastid (chloroplast) DNA regions in 177 individuals sampled from 22 natural populations of this species, and tested the hypothesis that its evolutionary history was markedly affected by Pliocene QTP uplifts and Quaternary climatic oscillations. Consistent with the taxonomic delimitation of the three morphologically divergent varieties examined, all individuals clustered into three genetic groups with intervariety admixture detected in regions of geographical overlap. Divergence between varieties was estimated to have occurred within the Pliocene and ecological niche modelling based on 20 ecological variables suggested that niche differentiation was high. Furthermore, modelling of population-genetic data indicated that two of the varieties (var. rubescens and var. linzhiensis) expanded their population sizes after the largest Quaternary glaciation in the QTP, while expansion of the third variety (var. likiangensis) began prior to this, probably following the Pliocene QTP uplift. These findings point to the importance of geological and climatic changes during the Pliocene and Pleistocene as causes of intraspecific diversification and range shifts of dominant tree species in the QTP biodiversity hot spot region.

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Stem-cell therapy has the potential to regenerate damaged heart tissue after a heart attack. Injectable hydrogels may be used as stem-cell carriers to improve cell retention in the heart tissue. However, current hydrogels are not ideal to serve as cell carriers because most of them block blood vessels after solidification. In addition, these hydrogels have a relatively slow gelation rate (typically >60 s), which does not allow them to quickly solidify upon injection, so as to efficiently hold cells in the heart tissue. As a result, the hydrogels and cells are squeezed out of the tissue, leading to low cell retention. To address these issues, we have developed hydrogels that can quickly solidify at the pH of an infarcted heart (6-7) at 37 °C but cannot solidify at the pH of blood (7.4) at 37 °C. These hydrogels are also clinically attractive because they can be injected through catheters commonly used for minimally invasive surgeries. The hydrogels were synthesized by free-radical polymerization of N-isopropylacrylamide, propylacrylic acid, hydroxyethyl methacrylate-co-oligo(trimethylene carbonate), and methacrylate poly(ethylene oxide) methoxy ester. Hydrogel solutions were injectable through 0.2-mm-diameter catheters at pH 8.0 at 37 °C, and they can quickly form solid gels under pH 6.5 at 37 °C. All of the hydrogels showed pH-dependent degradation and mechanical properties with less mass loss and greater complex shear modulus at pH 6.5 than at pH 7.4. When cardiosphere-derived cells (CDCs) were encapsulated in the hydrogels, the cells were able to survive during a 7-day culture period. The surviving cells were differentiated into cardiac cells, as evidenced by the expression of cardiac markers at both the gene and protein levels, such as cardiac troponin T, myosin heavy chain α, calcium channel CACNA1c, cardiac troponin I, and connexin 43. The gel integrity was found to largely affect CDC cardiac differentiation. These results suggest that the developed dual-sensitive hydrogels may be promising carriers for cardiac cell therapy.

Graphical AbstractHighlights d Inhibition of anterior vlPAG GABAergic cell activity induces feeding behavior d Activation of these cells reduces food intake in starving mice d Long-term manipulations elicit a corresponding change in mouse body weight d The BNST and LH regulate feeding via long GABAergic projections to the vlPAG