At an unprecedented scale, researchers have now catalogued the array of surveillance tools that plants use to detect disease-causing microbes across an entire species.

Representing a major advance for plant biology, the findings have important implications for the management of dangerous crop diseases which represent significant threats to food security.

Like animals, plants rely on immune systems to help them respond to attack by pathogenic microbes such as bacteria and fungi. A crucial layer of the immune system is formed by proteins called Nucleotide-binding Leucine-rich Repeat receptors (NLRs), which work together in combinations to detect the ever-changing array of microbes in the environment.

Despite progress in understanding how these receptors work together, key questions remained; what is the full spectrum of NLRs produced by plants? How much variation in NLRs is there in a typical plant species? What range is needed for plants to protect themselves?

An international team supported by the 2Blades Foundation through a grant from the Gordon and Betty Moore Foundation set out to piece together the NLR repertoire in the plant equivalent of the lab-rat, a mustard family species called Arabidopsis. The effort was carried out in the laboratories of Detlef Weigel, at the Max Planck Institute for Developmental Biology in Germany, Jeffery Dangl, of the Howard Hughes Medical Institute and the University of North Carolina at Chapel Hill, and Jonathan Jones at The Sainsbury Laboratory in the United Kingdom. Researchers from the University of Bath, Colorado State University, and the Center for Research in Agricultural Genomics (Barcelona) also contributed to the study, which is published today in the journal Cell.

The team sampled Arabidopsis plants, which come under attack by pathogens of all stripes, from populations across Europe, North America, and Asia. Using state-of-the-art sequencing technologies, they analyzed the genetic diversity of the plants’ NLRs. They found, as anticipated, that NLR repertoires in plants differed between locations, likely due to different evolutionary pressures from regional pathogens. But the team was surprised to find an upper limit on NLR gene numbers across the species.

As Weigel described the findings, “While the diversity is perhaps more limited than anticipated, it is the mixing of genes that makes each individual uniquely resistant to a different spectrum of pathogens.”

The study will also change the way researchers approach the subject in future, says Jones.

“One of the remarkable conclusions that emerge from this study is that so many populations need to be sequenced to define the full immune system repertoire of any plant,” he said. “Gone are the days when a single reference sequence is sufficient to reveal the secrets of a species; it is now clear that we need to understand the genetic diversity of a species in order to understand its immune system.”

The research has major implications for our understanding of agriculture and plant evolution. “This work will help drive new NLR receptor function discovery for developing disease-resistant crops and also guide the analysis of their evolution across the plant kingdom,” said Dangl.

Coordination and support for the study was provided by the 2Blades Foundation, an international organization dedicated to understanding plant disease and advancing durable crop disease resistance. Through its programs, 2Blades has already demonstrated in field trials that protection against serious unmanaged diseases can be expanded in crops by introducing resistance genes from related plant species. The fundamental knowledge of NLRs from the study will further inform strategies in its on-going programs, as well as the field of plant-microbe interactions at large. This study was funded in part by the Gordon and Betty Moore Foundation through Grant GBMF4725 to the 2Blades Foundation.

About 2Blades 
The 2Blades Foundation, based in Evanston, Illinois, is a 501(c)(3) charitable organization dedicated to the discovery, advancement, and delivery of durable disease resistance in crops. 2Blades establishes and manages development programs addressing significant unsolved crop disease problems in collaboration with leading research institutions around the world and at the 2Blades Group in The Sainsbury Laboratory, Norwich, UK. 2Blades manages a portfolio of specific traits and enabling technologies that it implements in its own programs and out-licenses for broad use. Visit the 2Blades website at http://www.2blades.org and follow 2Blades on twitter at @2blades.

About the Max Planck Society 
The Max Planck Society conduct basic research in the natural sciences, life sciences, and humanities. Since its foundation in 1948, eighteen Nobel laureates have emerged from its ranks. The Max Planck Society with its 86 Max Planck Institutes and facilities is the international flagship for German science, putting it on a par with the best and most prestigious research institutions worldwide. The more than 15,000 publications each year in internationally renowned scientific journals are proof of the outstanding research work conducted at Max Planck Institutes – and many of those articles are among the most-cited publications in the relevant field. Its self-concept of continuous renewal preserves the scope the Max Planck Society needs to react quickly to pioneering scientific developments.

About the University of North Carolina at Chapel Hill 
The University of North Carolina at Chapel Hill, the nation’s first public university, is a global higher education leader known for innovative teaching, research and public service. A member of the prestigious Association of American Universities, Carolina regularly ranks as the best value for academic quality in U.S. public higher education. Now in its third century, the University offers 74 bachelor’s, 104 master’s, 65 doctorate and seven professional degree programs through 14 schools including the College of Arts & Sciences. Every day, faculty, staff and students shape their teaching, research and public service to meet North Carolina’s most pressing needs in every region and all 100 counties. Carolina’s nearly 336,000 alumni live in all 50 states, the District of Columbia, U.S. Territories and 164 countries. More than 178,000 live in North Carolina.

About HHMI 
HHMI plays an important role in advancing scientific research and education in the US. Its scientists, located across the country and around the world, have made important discoveries that advance both human health and our fundamental understanding of biology. The Institute also aims to transform science education into a creative, interdisciplinary endeavor that reflects the excitement of real research. HHMI’s headquarters are located in Chevy Chase, Maryland, just outside Washington, D.C.

About The Sainsbury Laboratory 
The Sainsbury Laboratory (TSL) is a world-leading research centre focusing on making fundamental discoveries about plants and how they interact with microbes. TSL not only provides fundamental biological insights into plant-pathogen interactions, but is also delivering novel, genomics-based, solutions which will significantly reduce losses from major diseases of food crops, especially in developing countries. TSL is an independent charitable company and receives strategic funding from the Gatsby Charitable Foundation with the balance coming from competitive grants and contracts from a range of public and private bodies, including the European Union (EU), Biotechnology and Biological Sciences Research Council (BBSRC) and commercial and charitable organisations http://www.tsl.ac.uk.