Plant Programmed Cell Death Revisited

In plants, programmed cell death (PCD) is a genetically controlled pathway that eliminates specific cells. It is an integral part of the plant life-cycle from embryogenesis to senescence, and drives specialized developmental programmes such as leaf morphogenesis, differentiation of tracheary elements or formation of lysigenous aerenchyma in wetland species. PCD also occurs in response to environmental cues. Heavy metals, heat, UV radiation, waterlogging and salinity can induce PCD in order to isolate and remove damaged tissues, and potentially to amplify systemic stress signaling, thereby ensuring the survival of the organism. PCD is important in protecting plants from invading pathogens; a localized cell death (hypersensitive response) can be triggered in order to prevent pathogen spread to other parts of the tissue, however, the plant PCD machinery can be also hijacked: necrotrophic pathogens can secrete death manipulating toxins. Consequently, PCD is a ubiquitous process in plants that needs to be tightly controlled for normal growth, development and interactions with environment. The past two decades of research have uncovered a number of signalling pathways and cellular events associated with different types of plant PCD. Genetic studies have identified homologues of a number, but not all, of the animal apoptotic genes in plants, but also discovered plant specific PCD regulators. Intriguingly, while plant homologues do not exist for many of pro- and anti- apoptotic animal genes, their transgenic expression in plants has shown to dramatically affect the PCD pathway. This suggests a certain level of evolutionary conservation of PCD regulation between plant and animal kingdoms.

We believe that exciting times lie ahead for plant PCD research. The emergence of genome manipulation methods promises further insights into genetic regulation of PCD pathways. Availability of sequenced fern and bryophyte genomes will leverage studies of PCD evolution in land plants. Recently published cereal genomes pave the way to generate data that will not only advance our basic understanding of PCD pathway in plants, but also contribute to new strategies for development of more resilient crops with enhanced productivity.

This Research Topic focuses on studies (including Original Research, Perspective, Review articles) that summarize our current knowledge of plant PCD, stimulate new directions for future PCD research and report new insights into PCD understanding. In particular, we welcome submissions that investigate and discuss the following areas:

- Novel markers, methods and models for studying PCD in plants
- Signalling, regulation and execution pathways of plant PCD
- The role of PCD in crop stress tolerance and disease resistance
- Identification of new cell death-associated genes and its functions
- Transcriptional signatures of different types of plant PCD
- The evolution of PCD in plants