An Interview with Caroline Dean

Interview How Cool Is That: An Interview with Caroline Dean Jane Gitschier* Departments of Medicine and Pediatrics and Institute for Human Genetics, University of California San Francisco, San Francisco, California, United States of America Having grown up in Pennsylvania, I recall that late winter’s delight in spotting a purple crocus piercing through desiccat- ed gray snow, a harbinger for warmer days ahead. The eruption of the crocus, the bloom of the magnolia, and the flowering of winter wheat are all examples of plant processes that are not simply delayed by winter, but indeed require a sustained period of cold to proceed. Today’s interview journeys into the molecular under- pinnings of one such cold-dependent process: ‘‘vernalization.’’ Our guide is Caroline Dean from the John Innes Centre in Norwich in the United King- dom, and our destination is an ,10-kb genomic stretch of the humble Arabidopsis thaliana, a small white-flowering bit of greenery also known variously as thale or mouse-ear cress. A little background is in order here, as perhaps you, like me, had never heard the term vernalization. During the develop- ment of flowering plants, shoot growth occurs at the apical meristem, an undif- ferentiated mass of cells that can divide to make more stems, leaves, or flowers. While some plants are ‘‘rapid cyclers’’—i.e., they flower quickly after a short growth period—others require a duration of cold before they can flower, an evolutionary adaptation that allows them to resist flowering until the winter has ended. Often, varieties within a single species can exhibit one behavior or the other, such as spring and winter wheat, only the latter of which requires vernalization. Accessions of Arabidopsis vary in their vernalization requirement too, depending upon whether they grow along the Med- iterranean coast or above the Arctic Circle, for example. A few decades ago, when Arabidopsis Image 1. Caroline Dean. Photograph by Jane Gitschier. emerged as the plant of choice for doi:10.1371/journal.pgen.1003593.g001 molecular geneticists, Dean (Image 1) began to question how vernalization works at the mechanistic level: what genes are required for vernalization and how do vernalizing plants sense and remember the cold? She and her colleagues attacked the Citation: Gitschier J (2013) How Cool Is That: An Interview with Caroline Dean. PLoS Genet 9(6): e1003593. problem via three genetic routes, all of doi:10.1371/journal.pgen.1003593 which ultimately converged on the regu- Published June 27, 2013 lation of a single gene, FLC (FLOWERING Copyright: ß 2013 Gitschier. This is an open-access article distributed under the terms of the Creative LOCUS C), whose gene product is a Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, repressor of downstream flowering genes. provided the original author and source are credited. The ‘‘overwintering’’ accessions respond * E-mail: [email protected] PLOS Genetics | www.plosgenetics.org 1 June 2013 | Volume 9 | Issue 6 | e1003593 to cold by epigenetically silencing FLC, of a genetically engineered organism. John months of cold. It is an evolutionary enabling flowering to occur. This silencing offered me a position and I grabbed it. adaptation to make sure you don’t fully involves a conserved Polycomb complex Gitschier: Very exciting time. flower until spring. We still don’t know and associated PHD (plant homeodomain) Dean: You know, it was a dream. I really much about all of those processes proteins that modify histones at the FLC arrived in February—[in England] it was except for vernalization. locus. The FLC locus also produces cold, very dark, I had hardly any money. Vernalization is very important for many antisense transcripts known as ‘‘COOL- Then suddenly, here I was in California. crops, and winter and spring varieties have AIR,’’ which differ in their splicing and They loaned me a car. The salary seemed been bred independently. All the cereals— polyadenylation sites, and these assist in enormous. And sunshine! barley, wheat, rye—have winter and spring locking down FLC transcription in the Gitschier: Actually, our paths are varieties that the farmer sows either in cold. Once FLC is silenced, flowering can quite similar because I also did a postdoc October or in March. And a lot of the begin in earnest with the advent of longer in California with a young company at Brassicas, of course, most of the vegetables, and warmer days. These epigenetic chang- about the same time. It was the best four actually have a vernalization requirement. es are maintained throughout future cell years of my life, without a doubt. And what breeders have done is to breed divisions and even persist in cuttings Dean: Yes. Coming from a small plant for the need for different lengths of cold, so regenerated from the vernalized plants so lab in York, suddenly being exposed to this that you then have a nice supply for the that they do not need to be re-vernalized. amazing amount of information and supermarket year-round. However, when a seed is being produced, technology and ‘‘can-do’’ attitude, I was Gitschier: Well, the old-fashioned FLC silencing is removed so that the next just transformed bang! into a new way of cauliflower, before anybody bred in any- generation of plants also requires vernal- doing science. thing, when would that have appeared? ization. We had five successful years establishing The spring? I learned about Dean’s work just as I the fundamentals behind genetic engineer- Dean: Have you ever left a cauliflower was heading to the UK and quickly ing. And then, slowly but surely, financial or broccoli too long and then it’s sprouted? arranged to visit her on a Wednesday reality set in for these biotech companies. You actually get a beautiful flower coming afternoon in November. It was certainly The venture capital money ran out, and out of the top. my most active interview to date, as we research contracts with very specific goals Gitschier: No, but I’m keen to do that scooted out to the ‘‘barns’’ to see Arabi- replaced it. At that point it was a ‘‘we’’ experiment! dopsis and its Brassicaceae cousins—broccoli, rather than a ‘‘me,’’ so we looked around Dean: So, it’s an arrested meristem, the rapeseed, cauliflower—in all manner of for academic positions, and we took two bit we eat. leafing and flowering. This involved some here in Norwich. It was home, but also the Gitschier: The bit we eat is an robing and disrobing of bright red lab Sainsbury Lab had just been set up. arrested meristem! coats and hairnets with much humor along Jonathan [Jones, Dean’s husband] got Dean: Cauliflower is an earlier arrest the way. It has taken me a little while to the position there, and I came back to than broccoli, sort of little stubs, and if you digest this complex subject, but following the position at the John Innes. leave them longer, each one of the many its own ‘‘overwinter,’’ the interview has Gitschier: For me, going back to buds turns into a proper flower. now gone on to flower. academia from industry was appealing Gitschier: Cool. Gitschier: Let’s start with your choice because it was a new kind of a challenge. Dean: For the last couple of years, we’ve of a postdoc and how you got involved in In industry, I felt I knew what was had very extreme winters, but not always at the question of vernalization. expected of me, whereas in academia, it the same time. Last year after Christmas we Dean: I started off doing plant biology was a question of how creative I might be. had very, very cold temperatures. The year at York University. I did my PhD work on Dean: Yes, that’s right. I started to plan before, there was a famous satellite picture chloroplasts and then I wondered what on what to do in my own lab, and the answer of the UK all under snow before Christmas. earth I would do as a postdoc. My came from a sort of bizarre experience in Too much cold at any point can mess up supervisor had been on a sabbatical to California. I wanted to have a few bulbs in the scheduling of the broccolis and the Riverside [at the University of California], my apartment. So I bought some tulips, cauliflowers because they vernalize way too and she raved about it. I remember and the sales chap said to me, ‘‘Now don’t quickly and come into heading at about the thinking gosh, it sounds really exciting forget to put them in the fridge for six same time. So suddenly there was a glut of over there. weeks.’’ Of course, in England, you sow cauliflower and then months when there It was just at the time—1982—when it them in the ground in September, Octo- was no production in the UK after that. was discovered that a piece of the DNA ber, but you never think ‘‘why.’’ This was Gitschier: Ah, so it’s not just the from the plasmid in Agrobacterium [tumefa- how I learned about the requirement for duration of the cold but also the actual ciens] could be inserted into the plant prolonged cold for many plant processes: temperature. This is very complex. chromosome. So, genetic engineering was flower emergence in plants like tulips, Dean: It is. The current thinking born. A lot of money went in from venture breaking bud dormancy in trees, and describes vernalization efficiency in terms capital to start up new biotech companies, vernalization in many plant species. of the ‘‘day degree’’ exposure, but this is and John Bedbrook from New Zealand— Now vernalization is not quite the same poorly understood.

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