Plant—microbe encounters can be friendly or hostile. Densely colonized soil contains beneficial mycorrhizal fungi and rhizobia, which associate with roots and provide plants with mineral nutrients and fixed nitrogen, respectively, in exchange for carbon. By contrast, plants are constantly exposed to a range of fungal, bacterial and viral pathogens, and have evolved unique defense mechanisms to fight these infections. We hope you will enjoy this selection of papers covering recent scientific discoveries concerning these interesting and diverse relationships.

Proteins are transported across cellular membranes and between membrane-bound organelles inside vesicles by carrier proteins. Understanding these processes has been a major goal of cell biology for several decades. Increasingly, efforts are focusing on providing a molecular description of the structures and the latest advances in this area, which will be of interest to a wide range of biologists engaged in different fields of research.

One could argue that regenerative medicine is more theory than practice: only a handful of therapies such as skin grafts and heart transplants are happening today. However, research on regeneration of mammalian tissues and organs has intensified over the past decade, with the discovery of new ways to isolate and even create stem cells that can restore function, at least in rodents. Now the challenge—a formidable one—is learning what is necessary to make it work in patients. In this web focus, we have brought together content from Nature and Nature Reports Stem Cells to highlight where we are with the basic science, and the challenge of making medicine from stem cells, whether derived from adult tissue, reprogrammed cultured cells or embryos.

Over the last decade our understanding of plant signalling pathways has increased a great extent, in part due to the use of genetic tools in Arabidopsis. This has assisted in the identification of hormonal, developmental and environmental signal transduction pathways and cross-talk between them. A flavour of the excitement in the plant signalling pathways field can be obtained in the research articles and reviews presented in thisNatureweb focus.

This special Natureweb focus brings together exclusive coverage of the discovery, along with recent papers describing and utilizing cutting-edge technology for understanding and controlling brain and behaviour.

In recent weeks, the 'roadmap for peace' between Israelis and Palestinians has been all but torn up, thanks to suicide bombings and Israeli army raids in the occupied Palestinian territories. Amid this cycle of violence and despair, can scientific links between Israeli and Palestinian labs survive?

In 1918, a highly virulent form of the influenza virus killed at least 20 million people worldwide. Understanding the origin of the virus that caused this pandemic has been a long-standing goal because of the risk that a similar virus could arise and devastate human populations today. Produced with support from Retroscreen Virology Ltd.

Welcome to this Web Focus on Avian Flu, containing news and scientific reports warning about the potential for a new human flu pandemic in the near future.

Naturekeeps track of the key events and scientific discoveries as researchers assess the threat of another flu pandemic.

The regulation of cell cycle progression and cell division is at the heart of cell biological research. Understanding the central mechanisms also offers new insights into cancer biology. Gathered here is a selection of recent research and comment from the pages of Nature, including groundbreaking research from today's issue. This focus also includes our recentNatureInsight Cell division and Cancer.

Why do humans age, when fairly similar creatures (such as turtles) apparently do not? Here, we present the latest research on a molecule that appears to mimic the well-documented lifespan-extending attributes of eating fewer calories. Also featured is a comprehensive archive on ageing research, from nematodes to humans.

The slime mold Dictyostelium discoideumhas been an important laboratory model for over 50 years. These social amoebae normally live in forest soil where they hunt bacteria and yeast, and have therefore excelled in studies of how cells sense and move towards attractants in their environment.