QNAS QNAS QnAs with Detlef Weigel Sandeep Ravindran Science Writer

In his scientific career, National Academy microRNA mutant. Because of our past of Sciences member Detlef Weigel has gone work on development, it made a lot of sense from studying how fruit flies and flowers for us to look in more detail at the role of develop to investigating how adapt specific in growth and flowering. to different environments and the geno- PNAS: How did you come across the phe- mic variation that allows them to do so. nomenon of incompatibility, where Director of the Department of Molecular the plant’s own immune system can kill at the Max Planck Institute for hybrid progeny? Developmental Biology, Weigel has also Weigel: We had two strains of Arabidopsis made crucial contributions to studies of the fromthesamevillage,onethatflowered late of the plant immune system and and one that flowered early, and wanted to the role of microRNAs in plant development. find out the genetic basis for the flowering Weigel’s use of genomics technologies to study difference. My student, Janne Lempe, crossed the model plant has led the two strains together and made the sur- to a nuanced understanding of the variation prising observation that the progeny were in plant genomes, and could help prevent much smaller than their parents and barely diseases and increase yield in crop plants. grew, let alone flowered. We concluded that PNAS: What led you to study so many there must be an interaction between the two different subjects during your career? parent genomes that led to the progeny dying, Detlef Weigel. Image courtesy of Anne Weigel: When I discover a new problem another chance observation that launched Faden, MPI for Developmental Biology. that I haven’t thought of before, I often end a new area of research in my laboratory. up pursuing it, especially when few others are From gene-expression studies we realized already working on it. When I initially began that these plants mounted a pathogen re- Weigel: It used to be that you would study Arabidopsis studying the idea was to look at sponse even though there was no pathogen a single gene, and maybe its interaction with fl the development of ower organs, but instead around. Our hunch was that a factor from a few other genes, and make broad generali- ’ I became fascinated with the step before that, one parental genome detects a protein that s zations. Today the big picture has become fl the actual initiation of the ower. After I set coming from the other parent as being for- much more important. That’s especially true fi up my own laboratory at the Salk Institute eign, and we have since broadly con rmed in evolutionary biology, where it’s clear that I moved on to studying how a plant deter- this hypothesis. Because the two parent you always have to study many examples be- mines when to switch from vegetative growth genomes meet each other in every cell of fore you can make any generalizations. That fl to owering. This in turn led me and my the progeny plant, this behavior is triggered doesn’t mean that we have given up on con- Arabi- group to become curious about how in every cell and often the entire plant dies. ventional molecular and biochemical experi- dopsis strains from different places in the PNAS: Youhelpedestablishthe1001Ge- ments; I feel strongly that if you really want to fl Arabidopsis world manage to ower at different times. nome project for .Whatwasthe understand the consequences of evolution, We realized that knowing the entire genome goal of the project and what progress has you have to figure out how they manifest at sequences of different strains would make it it made? the level of individual genes and proteins. fi a lot easier to gure out how they differ in Weigel: The initial goal was to sequence PNAS: What are some of the applications fl Arabidopsis traits, such as the onset of owering. That 1,001 strains from all over the of your work? got us into large-scale sequencing, which world, to learn about the total amount of Weigel: Asking evolutionary questions in again has had a lot of offshoots, particularly genetic variation that is out there in the plants could help with a number of prob- in the area of evolution. For me this is the wild and how it is distributed. When we lems that we are facing. Feeding people on fi fun of being a biologist, as we will never started out ve years ago, sequencing 1,001 our planet is getting harder as the world run out of things to study. genomes seemed an ambitious goal, but we population keeps growing toward nine bil- PNAS: How did you discover the role of now have all of the sequences in hand and lion and the amount of arable land stays the fi microRNAs in plant development? expect to nish analyzing them within a few same or is even decreasing. It’s an issue that fi Weigel: We entered the microRNA eld months. The challenge has been to under- I’m very concerned about, and my hope is by chance. We had developed new genetic stand how much of the genetic variation is that what we learn about genetic variation fi technology to nd mutants based on overex- important in the natural context. Plants are a in Arabidopsis and other wild plants with pression of genes. One mysterious mutant good model for this because, unlike animals, relativelysimplegenomescaninformwork ’ made interesting-looking leaves, but we they can t run away, so you can take plants on crops, such as rice and corn. couldn’tquitefigure out what gene was being from Sweden and transplant them to Italy overexpressed. When microRNAs were first and vice versa, and ask how the natural var-

discovered in other systems, it dawned on us iation in their genomes affects how they do. This is a QnAs with a recently elected member of the National that maybe the overexpressed gene made a PNAS: How has technology changed how Academy of Sciences to accompany the member’s Inaugural Article microRNA. Sure enough, this was the first you do research? on page 17466 in issue 41 of volume 107.

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