A developmental geneticist s guide to roots Find out about the hidden half of plants

Transcription

1 the Centre for Plant Integrative Biology A developmental geneticist s guide to roots Find out about the hidden half of plants What do roots look like from the inside? How do roots form? Can we improve root systems to increase food production?

2 What is developmental genetics? How do multicellular organisms form? Preformation is the idea that the egg or sperm contains an embryo A preformed miniature infant, or homunculus, that simply becomes larger during development Figure 47.2

3 Developmental History of a Human

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6 Plants can change their developmental programme depending on environmental signals. Plants have amazing regenarative abilities.

7 How do plants form?

8 Only the rudimentary plant axis is set up during embryogenesis Cotyledon Shoot apical meristem Root apical meristem

9 A Developmental Biologists perspective: the root as a model organ Shoot apical meristem produces the shoot, leaves, inflorescences and floral organs. Smith et al, PNAS 2006 The root apical meristem produces just one organ: the root

10 Roots exhibit a wide variety of forms

11 The model organism Arabidopsis

12 Tracing cell lineages in the root.

13 Cell types in the root

14 We focus on just one cell type: protoxylem Xylem Transports water and minerals from root to shoot

15 Visualizing xylem cells Fuchsin highlights lignified tissue Toluidine Blue highlights the cell walls and cytoplasm

16 the Centre for Plant Integrative Biology We focus on just one question: what controls the positioning of xylem cells? Radial symmetry Bisymmetry Embryo Growing root

17 Be wary of what you read. DNA is not really a blueprint.

18 DNA provides a set of instructions whereby cells can self-organize

19 Central Dogma

20 Gene expression patterns in Fly embryos Nikon handbook of microscopy

21 We look for mutants affecting xylem patterning. The first one to be found was called wooden leg (wol) Mähönen et al. Genes & Dev 2000

22 WOL encodes a Cytokinin (Hormone)Receptor Hormone made in one cell Hormone moves to adjacent cells/tissues Hormone elicits a response in these cells

23 Altering levels of cytokinin signalling affect differentiation of protoxylem Reduced cytokinin signalling Increased cytokinin signalling

24 A protein AHP6 switches off cytokinin at the protoxylem position AHP6 gene activity ahp6 mutant Mähönen, Bishopp et al. Science 2006

25 Another hormone (Auxin) promotes AHP6 expression A protein PIN7 regulates the transport of Auxin PIN7 is regulated by.. Cytokinin

26 Auxin (hormone) PIN7 AHP6 Cytokinin (hormone)

27 the Centre for Plant Integrative Biology Mathematical model for vascular patterning Muraro et al., 2014 PNAS

28 the Centre for Plant Integrative Biology

29 the Centre for Plant Integrative Biology Model predicts an additional cytokinin inhibitor is needed in the metaxylem for ARR5 patterning

30 the Centre for Plant Integrative Biology Auxin response(dr5) PIN7 Spread of PIN7 to all of stele bar the metaxylem is predicted by the model when SHR / mirna is removed. This is also seen experimentally in the shr k.o. mutant.

31 Cell types in the root

32 the Centre for Plant Integrative Biology Why am I interested in xylem? Manipulation of xylem may affect water use efficiency in crops Narrow xylem 55 µm Unselected controls 65 µm Richards and Passioura, Aust. J. Agric. Res. 1989

33 the Centre for Plant Integrative Biology Work in Nottingham by Malcolm Bennett, Ranjan Swarup and Ive de Smet s groups is uncoupling the regulatory mechanisms controlling root architecture. Development of microct imaging(sacha Mooney) allows visualization of roots in soil. Sacha Mooney

34 Root hairs increase the surface area of roots enhancing water and nutrient uptake. Savage N, Yang TJW, Chen CY, Lin K-L, et al. (2013) PLoS ONE 8(10): e doi: /journal.pone

35 Thank you for listening