Signaling Systems Within The Plant: A New Era of Understanding

Transcription

1 Signaling Systems Within The Plant: A New Era of Understanding Phil Thomas Senior Agri-Coach Agri-Trend Agrology

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5 Factors affecting Yield and Rain & Snow Solar Radiation Evapotranspiration Carbon Dioxide Relative Humidity Wind Velocity Soil & Air Temperature Frost Free Days Oxygen Hail Flooding Rotation Crop & Pesticide Seedbed Firmness Pests Weed, Insects & Diseases Harvest/Swath Date Variety Seed Quality Quality Yield Seed Treatment Seeding Date, Rate, Depth & Speed Pesticide Choice & Timing Tillage Intensity Fertilizer Source, Rate, Placement & Timing Soil Type Organic Matter Soil Texture Soil ph Soil Aggregate Size Rooting Depth Field Topography Ion & Cation Exchange Capacity N, P, K, S, Ca, B, Cl, Mg, Mn, Mo, Fe, Zn levels Field location /latitude Soil Water Holding Capacity Soil Aeration Soil Water Infiltration Rates Soil Crusting Soil Drainage Field Slope

6 Management of Factors Due to multiple Stress factors crops do not reach their genetic yield potential Plants are continually exposed to abiotic and biotic stresses that negatively influence growth and development

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8 What is the most important input to crop production?

9 Maximizing Photosynthetic Efficiency Oxygen Nitrogen Hydrogen Carbon 2CO 2 + 2H 2 O C 6 H 12 O 6 + 6O 2 Potassium Nitrogen Phosphorus Oxygen Magnesium Calcium Sulfur Manganese Zinc Chloride Copper Boron Iron Molybdenum

10 Life Cycle in Plant Cells Most plant life cycle processes occur at the plant cell level regulated by genes. Every biochemical activity in a plant is regulated by genes!

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12 5.Trans - location 3.Synthesis How a plant works at the molecular level Lipids Cellulose Lignins Proteins Nucleic Acids - DNA, RNA Chlorophyll Growth Regulators Etc. Carbohydrates (including starch) Amino Acids + S + N 2. Respiration (Krebs Cycle) CO2 H2O 1. Photosynthesis Sugars Makes ATP Energy 4. Transpiration O2 CO2 & H2O

13 Think like a plant

14 Plant Genetics, Physiology and Biochemistry What s really changed in the past 10 years is: the shift from Genomics (number and types of genes involved) to Proteomics (protein products of the genes) and now Metabolomics (metabolites).

15 Vegetative growth: Germination, seedlings, shoots, roots and branches Reproductive growth: # of buds, flowers, pods, seeds, and seeds per pod Genes Regulate Yield: Biomass, plant height, dry matter, drought stress, heat stress, and leaf area index

16 Chemical composition: Hormones: Abscisic acid Auxins Cytokinins Ethylene Gibberellins Others Genes Regulate Proline content: (mineral elements) Improved enzyme activity For lignin content, Oil/protein content, Carbohydrates And amino acids Cytoplasmic streaming

17 Photosythesis efficiency: Leaf assimilation Total chlorophyll content and intensity Genes Regulate Water use efficiency Water management - through lower stomata resistance Higher intensity of transpiration Increased water uptake by roots

18 Hormones Plant signaling Systems (genes) Macro-proteins which are snippets of mrna sent from cell to cell via the phloem. (transport and defence against various stresses) Peptides Or PGR s

19 Signals are secreted in response to environmental factors (nutrient abundance, drought, light, temperature, chemical or physical stress) Plant signaling Hormones genes Peptides Or PGR s Germination, Rooting, Growth, Flowering, Foliage, Death

20 Hormone Levels STAGE I: Germination & Establishment STAGE II: Vegetative Growth STAGE III: Flowering & Reproduction STAGE IV: Fruit Sizing & Maturity Cytokinin Auxin GA Ethylene ABA Senescence Cell Initiation [ Cell Division ] Cell Sizing Cell Maturity Key Nutrient Hormone Co-factors: Ca, Fe, Mg, Mn, N, P, Zn, B B, Ca, Cu, Fe, K, Mg, Mn, Zn, amine N B, Ca, Cu, K, Mg, Mo, amine N B, Cu, K, Mg, Mn, Mo, P amine N

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22 Seed Germination Seeds imbibe 45% of their weight in water which leads to swelling and seed coat breakage. Genes activated hydrolytic enzymes break down stored oils and proteins into chemicals (+oxygen) for metabolism and growth. Oxygen is used in aerobic respiration for energy until the plant has leaves. Once the radicle emerges germination ends.

23 Cytokinin (CK) Root tips = factories of cytokinin synthesis (involved in hormone metabolism, up-take of macro-nutrients, protein synthesis + morphological response) Nitrate, sulfate and phosphate stimulates CK production in the roots and later in the shoots. In leaves CK involved in stomata opening + the above root factors.

24 Plant Signaling Systems Plants are good at math! Receptors (internal clock) within the leaves at night calculate amounts of starch available and estimate time to dawn. Signals adjust rate of consumption so the leaves don t starve from lack of energy until the sun returns. This helps the plants continue to grow in the dark Britain s John Innes Centre Journal of elife

25 Plant Signaling Systems Signaling systems allow plants to see, smell and feel (also movement). Plants have the ability to sense the environment and adjust their morphology, physiology and phenotype accordingly.

26 Plant Signaling Systems Plants perceive and can react to stimuli such as chemicals, gravity, light, moisture, infections, temperature, oxygen and carbon dioxide concentrations, parasite infestation, physical disruption, and touch. Plants have a variety of means to detect such stimuli and a variety of reaction responses.

27 Plant Signaling Systems (smell) For example a willow tree branch being attacked by tent caterpillars produces salicylic acid (SA) which makes its leaves taste bitter and unpalatable. This signal of SA is also released into the air and detected (smelled) by nearby branches or trees which then also produce SA providing protection. Lima beans attacked by an insect or bacteria do it too.

28 Plant Signaling Systems (smell) Wounded tomatoes are known to produce the volatile odour methyljasmonate as an alarm-signal when attacked. Plants in the neighbourhood can then detect the chemical and prepare for the attack by producing this or other chemicals that defend against insects or attract predators. [5]

29 Plant Signaling Systems (feel) The effect of touching a Mimosa plant with fingers causing the leaves to rapidly fold up. The cocklebur weed can die simply by touching it a few seconds for a few days

30 Photo Receptors These light sensors detect shading from neighbours and produce a signal auxin which causes some plants to grow taller. There are likely over 300 kinase proteins in canola with many diverse functions and pathways. These signals are involved in developmental and defence functions. (P-NB)

31 Plant Signaling Systems For example sunflowers with photo receptors send signals to slowly move heads with the sun. Another is the Venus fly trap. (movement)

32 Canola Life Cycle

33 Plant Signaling Systems Plants can see UV light (red & blue) via photo receptor proteins. Canola plants need over 10 to 12 hours of day length/day before the reproductive stage processes start.

34 GDD s (0 base)

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36 Reproduction B is essential Hours after plant receptors find required DL + GDD s FT gene in all leaves makes a signal molecule called FT protein. Transported by phloem to growing tip Acts on genes - turns stem cells into flower buds combines with and activates a FD protein from an FD gene. FT/FD signal

37 Immature Bud Canola Sex - Flowering Immature Stigma Immature anthers

38 Canola Sex - Flowering Flower opens within 2-3 days pollen is produced by anthers

39 Canola Sex - Flowering Anthers mature and release pollen Stigma tip has adhesive to capture pollen

40 Canola Sex - Flowering Pollen land on the stigma and absorbs water and nutrients from the stigma to germinate and form a pollen tube Over 100 pollen grains are required on the stigma to fertilize all the ovules

41 Pollen grain Stigma GABA Key signalling molecule that triggers pollination Boron is a precursor Pollen tube follows the signal and pollenates the 1 st ovule Ovules once 1 st ovule is pollinated the next ovary starts to send the signal etc 1 st ovule that matures sends out the GABA signal Takes only a couple of days or less for each flower for complete pollination

42 Pollen Tube If boron is deficient the tip of the pollen tubes will burst and no pollination will occur

43 Flowering From the start to the end of flowering there are about 8 to 9 Gibberellins involved that have effects on seed formation, proteins and oil. Gibberellins are also critical for root growth as they regulate numbers of cells and their size. K and Zn essential

44 Plants on Steroids Brassinosteroids from chloroplasts, join a protein on the surface of a plant cell and send signals to the cell's nucleus causing plant genes to be expressed. (P is important as the signal is a protein phosphatase). Chemical signals activate a cascade of gene activity regulating growth and development (response to gravity, light, & resist stresses).

45 Plant Signaling Systems Water movement is controlled by a cell membrane gene that produces an aquaporin (macro-protein) signal. This signal opens or closes cell membrane water/protein channels when drought or waterlogging occurs resulting in improved water use efficiency and movement. There are about 35 aquaporin s in plants. Phosphorus is important

46 Water Management Understanding how roots grow and how hormones control that growth is crucial to improving crop yields. A gibberellin protein signal plays a crucial role in controlling the size of the root meristem, and that it is the endodermis which sets the pace for expansion rates in the other root tissues.

47 Water Management Carbon is essential for all life! CO2 critical for photosynthesis. Plants open stomata during the day a problem - take in CO2 but lose water vapour.

48 Water Management When roots sense a water shortage they send a macroprotein signal to produce absicsic acid (ABA) that s translocated to the leaves which closes the stomata. K & Ca are NB

49 Water Management ABA triggers a signalling cascade in stomatal guard cells which closes the stomata reducing water loss. ABA induces the production of H 2 O 2 in guard cells which then activate calcium channels Both ABA and H 2 O 2 induced Ca channels are important mechanisms for stomata closing. Therefore K and Ca are important

50 Signals Involved with Nutrients It is important to understand the molecular basis of nutrient uptake and transport within the plant and the genes responsible Uptake and transport of nutrients are gene regulated by signals

51 Signals Involved with Nutrients For example there are 14 genes (that we know of) involved in the transporters (uptake and transport) of sulphur within the plant These genes are in 5 groups (in the roots, leaves, stems and cell to cell) There are many more genes regulating transporters of Mg (7) N (37) and P (142)

52 Signals Involved with Nutrients Where S is deficient = big yield loss But if S is added then uptake of Se and Mo is decreased due to the sulfate transporter expression and competition from Mg, N & P transporter genes. But if Mg, N & P up-regulated genes are switched on S uptake is increased

53 Nutrients Involved with Signals Nutrients are critical for the production of signals and/or for the products produced (metabolites, enzymes, etc.) For example biological nutrients are key for making enzymes: Ni (2) Mo (4) Mn (50) Fe (100) Cu (100) Zn (1200)

54 Nutrients Involved with Signals While Mo is only involved with 4 enzymes it is critical for plant growth Nitrate reductase no N nutrition without Mo Sulfite oxidase NB in chloroplasts Zanthize dehydrogenase disease defense Aldehyde oxidase NB in hormone signals metabolism (cytokinins, ABA, Auxins, ROS Mo is a cofactor for Moco sulfurase (MG, S & Fe) a protein for drought tolerance.

55 Nutrients Involved with Signals There are a large # of genes that regulate molecular processes that respond to K. Jasmonic acid a defence metabolite K is involved in signals for accumulation of secondary Jasmonic defense metabolites for fungal, bacterial, viral and insects attacks. Therefore, plants are healthier.

56 Nutrients Involved with Signals Cu, Zn & Mn are co-factors for a large number of enzymes such as SA which results in systemic acquired resistance improving disease resistance. There is a synergism with seed treatments and seed quality, health and yield.

57 Protection Response Plant with no stress (weather, nutrients, disease, water, good rooting depth, etc) may only have 3 genes (turned on or off) so there is limited resistance activity. But in plants with stress there may be 60 to 70 genes which are strongly affected under stress (and turned on).

58 Protection Response SAR systemic acquired resistance that is dependant on phytohormone salicylic acid. An attacking pathogen secretes effectors (Avr) that are recognized by plant resistance proteins (R) which trigger the development of hypersensitive response (HR) which activates a SAR signal.

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60 Protection Response The SAR signal leads to production of protection proteins (PR) throughout the plant which act against a broad spectrum of the same or other pathogens. One of these is the Shikimic acid pathway (phyto alexins) which takes away nutrients from around the disease infected areas starving the disease. P is important.

61 Shikimic Acid Pathway

62 Protection Response Attacks by predators/diseases trigger signals that provide defense. In canola there is a glucosinolate/myrosinase system triggered that produces more glucosinolates and trichomes which are stored in the cell vacuoles to protect the plant.

63 Protection Response The high levels of glucosinolates may deter some insects/diseases BUT may also attract specialist bugs through phenols that are given off by the plant. Sulphur is essential for production of glucosinolates.

64 Conclusion Understanding precisely how plant signaling systems and hormones regulate plant growth is one of the key areas of fundamental plant biology which will underpin crop improvements in the future!

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66 Thank You