Dr Andy Plackett BA (Hons.), PhD

Dr Andy Plackett

School of Biosciences
Royal Society University Research Fellow

Dr. Andy Plackett is a Research Fellow tackling one of the remaining great black-boxes in plant evolution, how plants evolved seeds. To do this he is pioneering the use of functional genetic analysis in ferns, the closest seedless relatives of seed-bearing plants, to understand how genetic networks and gene functions changed during the origin of the first seeds compared to their spore-bearing ancestors.

Qualifications

2012 - PhD, Plant Sciences, University of Nottingham/Rothamsted Research
2005 - BA (Hons), Biological Sciences, University of Oxford

Biography

A developmental geneticist (and Reluctant Microscopist) by training, Andy undertook his PhD at Rothamsted Research, studying the role of the plant hormone gibberellin in floral development and fertility of the model plant Arabidopsis thaliana. He has since worked as a postdoc at the University of Oxford (researching plant shoot evolution) and the University of Cambridge (researching rice leaf cell development).  As a postdoc he helped to establish new methods for functional genetic analysis in the fern lineage of plants, allowing us to use the fern Ceratopteris richardii (not a dinosaur, sorry!) as a first fern genetic model.

In 2019 Andy was awarded a Royal Society University Research Fellowship with the goal of using ferns to understand how the reproductive mechanisms of seed-bearing plants evolved, which he is undertaking within the School of Biosciences.

Teaching

Andy is not presently involved in any undergraduate taught courses within Biosciences.  If anyone is interested in applying for a research project in his lab as part of their undergraduate degree, please get in touch.

Postgraduate supervision

If you are interested in possible upcoming postgraduate opportunities in the lab, please get in touch with Andy.

Research

Have you heard of the seed revolution? 

The fact that plants reproduce by making seeds is so basic that most of us don’t even stop to think about it, but seeds are crucial to us as a source of nutrition.  Seeds represent the end-point of a highly complex and varied sexual reproductive process in plants, frequently produced within specialized edible lures (aka fruit) that plants will only make if they detect that seeds are developing inside of them.  The vast majority of our agricultural crops are therefore the products of this specialized reproductive process, and with climate change and increasing pressure on our agricultural systems our future food security is dependent on improving our understanding of how plants do this.

Plants that make seeds are so commonplace today it is easy to assume that this has always been the case, but seeds are in fact an evolutionary (and revolutionary) innovation by one group of plant relative newcomers that proved so successful it has changed the face of life on Earth.  Plants originally reproduced without seeds, instead dispersing single-celled spores much more similar to modern pollen (Figure 1).  This switch from spores to seeds involved numerous complex changes in plant development- not just the seed itself, but also the invention of dedicated male and female haploid sexes, specialized reproductive structures (flowers and the carpel) and the process of pollination. How this revolution in plant reproduction was achieved remains one of the great unanswered questions of plant evolution, and answering this question can provide us with important insights into the mechanisms that control seed-based reproduction in modern plants

A collage of images featuring seed plants during reproduction.

Figure 1. A quick comparison of seed-bearing and seedless plant reproduction:
The seeds of flowering plants (angiosperms) (A) contain a dormant plant embryo inside a protective coat together with a dedicated food supply (endosperm). Angiosperm seeds form inside the carpel (Cp) of the flower (B). Seed-bearing relatives of angiosperms, the gymnosperms, instead produce ‘naked’ seeds, for example between the scales of a pine cone (C). In place of seeds, ferns produce single-celled spores on the underside of their leaves (D, E), in special structures called sporangia or ‘sorii’ (So). Each spore germinates into a multi-celled photosynthetic ‘gametophyte’ (F), which eventually makes egg cells inside special reproductive organs called archegonia (Ar). Once fertilized inside the archegonium (G), this egg develops into an embryo (Em) on top of the gametophyte, which provides it with food through a placenta (Pl). This phase of vegetative growth present in seedless plant gametophyte development has been drastically reduced in seed-bearing plants, with the gametophyte now growing entirely inside the developing seed.

The model fern, Ceratopteris richardii, in full ‘flower’

My research group is focused on investigating the evolution of seed-based reproductive systems at the level of the genetic circuitry that controls them.  Survivors of the older, seedless plant families from which seed-based reproduction arose are still alive today, the most closely related to all living seed-bearing plants being the ferns.  However, to-date astonishingly little is known about the genetic pathways that control development and reproduction in seedless plants.  Using new experimental tools in these seedless plant groups (such as genetic modification of the fern Ceratopteris richardii1,2, Figure 2 and 3), we aim to compare genetic networks and gene functions between seedless and seed-bearing plant reproductive systems to identify what genetic changes took place during the origin of seed-bearing plants and how they have diversified since.

 

 

Figure 3. The model fern, Ceratopteris richardii, in full ‘flower’

Current Research projects 

The lab is currently working on projects to compare the function of regulatory genes (transcription factors) found in both ferns and seed-bearing plants, where these genes have an important role in controlling reproduction in the model flowering plant Arabidopsis thaliana.  Previously we found that the LEAFY floral regulator functions in vegetative development in ferns (Figure 3), suggesting that the genetic network controlling floral development first arose from a vegetative shoot.1 We are now focusing on the MADS-box genes, which in Arabidopsis act downstream of LEAFY to specify the identity of developing seeds and other floral organs.

three images of fern fronds at different stages of life.

 

 

 

 

Figure 3. Mapping LFY gene expression in C. richardii with a transgenic reporter. Fern fronds taken from plants of different ages (A, 20 days; B, 60 days; C, 124 days) showing blue staining wherever the gene CrLFY1 is being expressed. This gene is a master regulator of floral development- we didn’t expect to find this supposedly reproductive gene involved in fern leaf development!  Taken from Plackett, Conway et al. 20181.

References
1. Plackett, Conway et al. (2018), eLIFE 7: 39625
2. Plackett et al. (2014), Plant Physiology 165: 3

Publications

Plackett ARG*, Conway SJ*, Hewett Hazelton KD, Rabbinowitsch EH, Langdale JA, Di Stilio VS (2018). LEAFY maintains apical stem cell activity during shoot development in the fern Ceratopteris richardii. eLIFE 7: 39625. DOI: 10.7554/eLife.39625
*Joint First Authors

Plackett ARG*, Powers SJ, Phillips AL, Wilson ZA, Hedden P, Thomas SG (2018). The early inflorescence of Arabidopsis thaliana demonstrates positional effects in floral organ growth and meristem pattering. Plant Reproduction 31: 171. DOI: 10.1007/s00497-017-0320-3 
*Corresponding Author

Plackett ARG, Coates JC (2016). Life’s a beach- the colonization of the terrestrial environment.  New Phytologist 212: 831. DOI: 10.1111/nph.14295

Plackett ARG, Wilson ZA (2016).  Gibberellin and plant reproduction. In Annual Plant Reviews Volume 49: The Gibberellin Plant Hormones (Hedden, P. and Thomas S.G., eds) pages 323-358, Blackwell, Oxford. DOI: 10.1002/9781119210436.ch11

Plackett ARG, Di Stilio VS, Langdale JA (2015).  Ferns: the missing link in understanding shoot evolution and development in land plants.  Frontiers in Plant Science 6: 972. DOI: 10.3389/fpls.2015.00972

Plackett ARG, Rabbinowitsch EH, Langdale JA (2015). Protocol: Genetic transformation of the fern Ceratopteris richardii through microparticle bombardment.  Plant Methods 11: 37. DOI: 10.1186/s13007-015-0080-8

Plackett ARG, Huang L, Sanders HL, Langdale JA (2014). High-efficiency stable transformation of the model fern species Ceratopteris richardii via microparticle bombardment.  Plant Physiology 165: 3. DOI: 10.1104/pp.113.231357

Plackett ARG, Ferguson AC, Powers SJ, Wanchoo-Kohli A, Phillips AL, Wilson ZA, Hedden P, Thomas SG (2013). DELLA activity is required for successful pollen development in the Columbia ecotype of Arabidopsis.  New Phytologist 201: 825. DOI: 10.1111/nph.12571 

Plackett ARG, Powers SJ, Fernandez-Garcia N, Urbanova T, Takebayashi Y, Seo M, Jikumaru Y, Benlloch R, Nilsson O, Ruiz-Rivero O, Phillips AL, Thomas SG, Wilson ZA, Hedden P (2012).  Analysis of the developmental roles of the Arabidopsis gibberellin 20-oxidases demonstrates that GA20ox1, -2 and -3 are the dominant paralogs.  Plant Cell 24: 941. DOI: 10.1105/tpc.111.095109

Plackett ARG, Thomas SG, Wilson ZA, Hedden P (2011).  Gibberellin control of stamen development: a fertile field. Trends in Plant Science. 16: 568. DOI: 10.1016/j.tplants.2011.06.007

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