Reviews & Analysis

New research backs the contentious idea that solid tumours are not masses of equivalent cells, but instead contain cancer stem cells that support tumour maintenance. Here, two experts provide complementary views on the findings and on the implications for potential therapies. See Letters p.522 & p.527

Predicting plant responses to increasing temperatures is integral to assessing the global impact of climate change. But the authors of a comparative study assert that warming experiments may not accurately reflect observational data. Climate and ecosystem scientists discuss how impact prediction should proceed. See Letter p.494

A meta-analysis of agricultural systems shows that organic yields are mostly lower than those from conventional farming, but that organic crops perform well in some contexts. Agricultural scientists discuss whether the conclusions of the study should change farming practices and management. See Letter p.229

An article suggesting that allergic responses may not be an accident of an off-target immune system, but rather a deliberate defence against potential harm, provokes the question of whether our understanding of allergy needs an overhaul. Immunologists provide their opinions. See Perspective p.465

An analysis of the intensity and polarization of sunlight reflected by Earth reveals signatures of life on our planet. What prospects are there for using similar measurements to find life on planets outside the Solar System? Planetary scientists offer some answers. See Letter p.64

In the cell, genomic DNA is transcribed into various types of RNA. But not all RNAs are translated into proteins. Does this give protein-coding RNAs greater credibility in terms of function? Views differ.

Purkinje cells in the brain region known as the cerebellum act by inhibiting their target neurons. A paper in this issue provides an explanation for how this inhibition might be used to control the timing of action potentials. But experts are not equally convinced about the functional relevance of this finding. See Letter p.502

Materials that refract light backwards are thought to be required for making super-resolution lenses. An alternative proposal — that conventional, positively refracting media can do the job — has met with controversy. Two experts from either side of the debate lay out their views on the matter.

The collapse of the Maya civilization is often attributed to drought, but is the explanation really as simple as that? On the basis of evidence from their respective fields, an archaeologist and a palaeoclimatologist call for a more nuanced assessment.

A technique called somatic-cell nuclear transfer has been applied to human oocytes, resulting in the generation of personalized stem cells, albeit genetically abnormal ones. Two experts discuss the biomedical significance of this work and the ethical issues surrounding the use of human oocytes in research. See Article p.70

Increased expression of sirtuin proteins has been shown to enhance lifespan in several organisms. New data indicate that some of the reported effects may have been due to confounding factors in experimental design. Here, experts discuss the significance of these data for research into ageing. See Letter p.482

Variation in a genomic region that contains the cancer-associated gene ATM affects a patient's response to the diabetes drug metformin. Two experts discuss the implications for understanding diabetes and the link to cancer.

Two approaches have emerged for creating libraries of compounds for use in biological screening assays for drug discovery — fragment-based ligand design and diversity-oriented synthesis. Advocates of each approach discuss their favoured strategy.

A growing body of literature deals with the application of theories developed in other disciplines to financial institutions, to which a paper in this issue now adds. As outlined here, however, views differ as to its relevance. See Perspective p.351

Many scientists now use the power of computer models to advance their subjects. But there is a choice: to simplify complex systems or to include more detail. Modelling the intricate processes of sedimentary geology is a case in point.