Climate change and seed dormancy in tropical areas: an ecological and genetic perspective.

Transcription

1 Climate change and seed dormancy in tropical areas: an ecological and genetic perspective. Henk W.M. Hilhorst Wageningen Seed Lab Lab. of Plant Physiology Wageningen University The Netherlands

2 The world is getting warmer...

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5 drier

6 Water level in the Jaguari reservoir in Sao Paulo, Brazil, following the 2014 drought. August 2013

7 Water level in the Jaguari reservoir in Sao Paulo, Brazil, following the 2014 drought. August 2014

8 Loss of arable land in the coming decades

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10 Predicted drought until the end of the century

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13 Growing coffee in Siberia?

14 Brazil: The world's top coffee producer Intergovernmental Panel on Climate Change (IPCC) A 3ºC rise in temperature and a 15% decrease in rainfall from pre-industrial levels in Minas Gerais and Sao Paulo, could reduce the potential area for coffee production from 70-75% to 20-25%.

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16 How does seed performance change in a changing climate and, if so, what are the consequences?

17 For wild seeds? Biodiversity at stake? For crop seeds? Food security at stake?

18 The occurrence of dormancy throughout climate zones of the world

19 How does the environment influence seed dormancy (and seed quality?) 1. Prevailing environment 2. Parental environment 3. Prevailing X Parental environment

20 Very complex interactions Walck et al., Global Change Biology 2011

21 The soil seed bank Timing of emergence is determined by flowering time and dormancy

22 Example Physical dormancy Wikipedia Acacia suaveolens Dillwynia floribunda

23 After-ripening Example Physiological dormancy Summer conditions Spring conditions

24 Longer after-ripening period before rainfall favours species with lower temperature optima for germination now predicted Walck et al., Global Change Biology 2011

25 Requirement for cold/warm stratification to break dormancy Plasticity of response Duration of cold period Walck et al., Global Change Biology 2011

26 Shifts of germination phenology of seeds requiring cold stratification now future future now shortened winters: partial dormancy break premature spring warm-up accelerates germination. Walck et al., Global Change Biology 2011

27 Dormancy cycling: The depth of dormancy is continually changing through induction and relief in response to a range of environmental signals. Arabidopsis (Cvi) Germination Temperature (%) ( C) C 10 C 15 C 20 C 25 C Days after-ripening, post-exhumation Soil moisture content (%) to 50% germination (AR50) Suitable time of year 0 0 Oct-07 Dec-07 Feb-08 Apr-08 Jun-08 Aug-08 Oct-08 Oct-07 Dec-07 Feb-08 Apr-08 Jun-08 Aug-08 Oct-08 Exhumation date Temporal signals Suitable conditions for germination Spatial signals 0 0 e.g. Temperature e.g. Light, Nitrate Environmental signals remove successive layers of dormancy to complete germination at an optimum time Footitt et al, Plant J. 74:

28 What are the molecular mechanisms of dormancy cycling and how are these regulated by environmental factors? We re only scratching the surface, but

29 DELAY OF GERMINATION 2D Graph 3 25 Summer annual DOG1 relative expression DOG1 Soil temperature Soil temperature at 5cm (oc) Cvi Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Calender Time Depth of dormancy (sensitivity to spatial signals) Winter annual DOG1 relative expression Soil temperature at 5cm ( C) Bur 0 Oct/09 Dec/09 Feb/10 Apr/10 Jun/10 Aug/10 Oct/10-5 Calender time DOG1 expression is highly negatively related to soil temperature in both Cvi and Bur, but dormancy patterns differ.

30 DELAY OF GERMINATION ABA ng g -1 DW DOG1 ABA ng/g DOG1 Relative Expression Depth of dormancy. Days to AR50 DOG1 is a thermal sensing mechanism setting dormancy level via altered sensitivity to background ABA in different ecotypes. Footitt et al, Plant J. 74:

31 Sensitivity to spatial environmental signals changes and when this coincides with a suitable environment seed germination is completed Temporal signals Spatial signals Footitt et al, Plant J. 74: Finch-Savage and Footitt, J Expt Bot 68:

32 Nitrate content Light quality Seasonal temperatures determine overlap of germination window with field temperature, light- and nitrate thresholds 40 Max Field temperature, C [nitrate] P fr /P tot T field Min 0 Oct Jan Apr Jul Oct Time Hilhorst, 2007

33 A schematic model of dormancy cycling and germination timing LIGHT Ambient TEMPERATURE NITRATE Ambient Output: DOG1 + other factors Increasing sensitivity GA Sensitivity ABA Increasing sensitivity Output: GA-synthesis (GA3ox1) GA/ABA-signaling Output: ABA degradation (CYP707A2) Dormancy relief Dormancy induction Dormancy cycling Finch-Savage and Footitt, J Expt Bot 68;

34 Conclusions on seed ecology and climate change Seeds respond to many environmental signals

35 Conclusions on seed ecology and climate change - Extremely complex: multiple interactions - Plant plasticity - Plant adaptability - Prediction per species, per climate zone - Seed bank dynamics: after-ripening/stratification

36 Parental Environment heathermccorkle.blogspot.com

37 Parental environment x plant development (= seed quality) N P K

38 The effects of the parent environment on seed germinability (Seed Science Research, 1991) M. Fenner a1 a1 Biology Department, Southampton University, Southampton SO9 5NH, UK Abstract. This has been demonstrated in numerous species, both wild and cultivated. The evidence comes from field observations and controlled experiments. A survey of the literature shows that some well defined patterns emerge, with certain environmental factors tending to have similar effects over a wide range of species. The effects are probably the result of changes in the quantity, mobility or activity of growth substances such as abscisic acid. The ecological implications of the phenomenon are briefly discussed.

39 Temperature Arabidopsis thaliana grown at 3 temperatures 20 C 15 C 10 C Kendall S L et al. Plant Cell 2011;23:

40 Temperature of the parental environment is the most dominant factor determining seed performance Principle component analysis of 124 metabolites of seeds produced at: High light Low light Low temperature Low nitrate He et al., 2014

41 Networks of metabolites Carbon 20 C Nitrogen 15 C

42 (Maternal) temperature perception and signal transduction ICE1 HOS1 Modified from Kendall S L et al. Plant Cell 2011;23: PATENT: WO A1

43 The hos1 mutant is insensitive to maternal temperature PATENT: WO A1

44 Environmental factors play a dual role Parental Prevailing He et al., 2013

45 A case study: High temperature + drought: The green seed problem in soybean yellow green

46 Normal conditions Chlorophyll is completely degraded during maturation

47 Causes of Chlorophyll Retention High temperatures Drought + Genetic Components Severe rust Drying temperature nd nd nd = not detected

48 Consequences of Chlorophyll Retention Chlorophyll retention = lower seed quality Viability Vigor Longevity Grade standards for acceptable green seed percentage: Brazil = 8% USA = 1% Dark-colored oil Rancidity

49 Presence of chlorophyll in seeds = lower seed quality

50 Chlorophyll vs Seed Quality Lot 74,5 % green seeds 110 lots Green seeds Yellow seeds Green seeds Photos: Daiani Ajala Luccas

51 Oil quality MINISTÉRIO DA AGRICULTURA, PECUÁRIA E ABASTECIMENTO IN Nº 49, of DECEMBER 22, 2006 (BRASIL, 2006): define the characteristics of identity and quality of refined vegetable oils. Sensory characteristics, color, impurities, composition of fatty acids, stability index, peroxide index, unsaponifiable matter, smoke point, etc... IN Nº 11, of MAY 15, 2007 (BRASIL, 2007): establish the Soybean Technical Regulation. Green Seed In-natura consumption: up to 4% Other uses: up to 8%

52 Presence of chlorophyll in seeds = lower oil quality Green Seeds: Reduction of up to 3% of the total amount of oil Higher acidity Higher refining cost Lower quality in storage light - oxidation Oxidation of the oil is influenced by the composition of fatty acids, oil processing, light, temperature, concentration and type of oxygen, free fatty acids, mono and diacylglycerols, transition metals, peroxides, thermally oxidized compounds, pigments and antioxidants.

53 Chlorophyll (mg/kg) Oxidative Stability 110 C (h) Example: Cultivar W799 Tocopherols and Tocotrienols (mg/100g) Green Seeds Yellow Seeds Green Seeds Yellow Seeds

54 How to address the green seed problem?

55 Some research questions 1. Does chlorophyll directly affect soybean seed quality? Or is it just a marker for the stage of seed ripening? 2. Why do seeds have chlorophyll, if it is potentially damaging? Biological role? 3. Can we dissect the environmental from the genetic causes of green seeds?

56 Approaching the Green Seed Problem STEP 4 Molecular markers for breeding/genes for genetic modification STEP 1 Chlorophyll vs seed/oil quality STEP 3 Molecular control of chlorophyll degradation STEP 2 Molecular characterization of chlorophyll retention

57 Collaborators José França Neto Fernando Henning Lilian Henning Silvana Marin Francisco C. Krzyzanowski Edvaldo A Amaral da Silva Henk WM Hilhorst

58 Learning from seeds: How to counteract damage from drought?

59 In orthodox seeds drying is integrated in their normal development and, thus, they are desiccation tolerant

60 Xerophyta viscosa: a seed in plant s clothing? A resurrection plant

61 Xerophyta viscosa rehydration

62 Transcriptomics of dehydration/rehydration cycle of mature X. viscosa leaves

63 Co-expression networks during dehydration of mature X. viscosa leaves. Seed-specific ABI3 regulon Monke et al. (2012 ) Nucleic Acids Res. 40:

64 The DT switch + drought Reintroduction of vegetative DT in desiccation sensitive crops

65 Final conclusions

66 Greatest challenge for the future: Design new crops (and seeds!) that are adapted to climate change Plant breeding climate smart agriculture Integrated molecular-genetics and genomics CRISPR-Cas9 for gene/genome editing Biologicals and chemical stimulants

67 Thank you for your attention!