phyllosphere

phyllosphere is a dynamic rapidly changing area surrounding the germinating seed. there are two categories of microbes one is positively enhancing and negatively reducing the plant yield

1. Doctoral seminar on “ New insights into the structure and functional dynamics of phyllosphere microflora ” By YALAVARTHI NAGARAJU, Ph.D (Ag)

2. Classification

3. Which part of the plant doesn’t contain microbes ?

4. Kinds of stresses Seasonal cycle Developmental, morphological changes in plant Day and night cycle Limitations of nutrients Physiochemical constraints (light, temperature, radiation, desiccation)

5. How they survive on the leaves? Tolerance strategy which permits the inhabitants to tolerate direct exposure to environmental stresses on the surface of the leaf mainly UV radiation and low moisture conditions Eg : Saprophytes typically employ tolerance strategies to survive in the foliar zone, as they cannot survive endophytically Avoidance strategy which allows the epiphytes to colonize sites that do not face these stresses (Beattie and Lindow , 1995 ) Eg : Foliar pathogens can utilize both the strategies to harbour the plants more efficiently

6. Hotspots on leafs Bases of trichomes , Stomata, Epidermal cell wall junctions and Grooves along veins ( Beattie & Lindow , 1999 )

7. Introduction Phyllosphere is the surface and interior of the aerial parts of vascular plants (Newton et al., 2010) Most of the phyllosphere colonizing microorganisms live as commensals on their host plants About 0.1–8.4 % of the total bacterial population were cultivable ( Rastogi et al., 2010 ) The phyllosphere has an area of roughly about one billion square kilometres (Morris and Kinkel , 2002), in which the number of bacteria may reach up to 10 6 –10 7 cells per square centimetre of leaf area, which is roughly 10 26 ells

8. History 1955 - The term phyllosphere was first introduced by the plant pathologist F.T. Last 1956 - “ Phyllosphere ” term was coined by Ruinen 1987 - Kinkel tested the equilibrium theory of island biogeography , assuming that individual leaves form discrete habitat patches for microbes analogous to oceanic islands for macroorganisms . 2002 – Morris extended the concept to include both the areas inside and outside the leaf 2012- Berlec considered phyllospheric microflora as “Plant probiotics” 2015- Doan and Leveau divided the phyllosphere into two unique niches i.e., Phylloplane ( the leaf surface landscape) and phyllotelma ( the leaf surface waterscape)

9. How they will solve the problem of carbon, energy?

10. Research article

11. Picea abies Cinara spp

12. No.of trees No.of twigs/tree Natural predators attack Overwintering eggs Low egg densities

13. L1-L4 Larval instars C. pruinosa C. pruinosa C. pilicornis bud stage End of bud extension stage End of shoot extension phase

14. May (Spring ) July (mid summer) September Complete medium Mineral medium with NH 4 + Mineral medium with NO 3 -

15. Structure of phyllosphere microflora

16. Community structure

17. Ecology of phyllosphere microbiota Actinobacteria Bacteroidetes Firmicutes Proteobacteria ( Bulgarelli et al., 2013) Pseudomonas Sphingomonas Methylobacterium Bacillus Massilia Arthrobacter Pantoea Species richness in fungi is one order of magnitude lower than that of bacteria ( Finkel et al., 2011).

18. Core phyllosphere community of crops Rice Rhizobium, Methylobacterium , and Microbacterium , Lettuce Pseudomonas, Bacillus, Massilia , Arthrobacter , and Pantoea Soybean, clover, Arabidopsis Sphingomonas , Methylobacterium

19. Phyllosphere microbial community in green house conditions

20. Major drivers of phyllosphere microbiota composition Geographical location Eg : 1 salt excreting desert tree Tamarix In this plant major determinant of phyllosphere microbial community structure is geographical location. It is evidenced by the fact that different species of Tamarix ( T. aphylla , T. nilotica , T. teragina ) grown in same geographical location supported similar bacterial community whereas, plants grown in different locations showed strong correlation with geographical differences ( Finkel et al., 2012) Eg : 2 similar results were found in lettuce crop, increased distance between lettuce production sites resulted in more diverse community structure ( Rastogi et al., 2012)

21. Unlike plants and animals, bacteria did not exhibit an elevational gradient in their diversity ( Fierer et al., 2011)

22. 2) Climatic factors

23. Research article

24. 3) Plant genetics Phyllosphere communities associated with Pinua ponderosa were fairly similar to each other irrespective of the geographical location ( Whipps et al., 2008) A microbial survey of different cultivars of lettuce grown in the same field showed that they supported different bacterial communities on their foliage (Hunter et al., 2010) It was suggested that these differences correlated with plant genetic components that regulate leaf texture and the leaching of metabolites to the leaf surface

25. Is it possible to manipulate community structure? Yes, we are already doing it…..

26. Research article

27. functions of phyllospheric microflora

28. Production of growth promoting hormones Production of pigments Production of volatile organic compounds Extracellular oligosaccharides Cross kingdom signals Quorum sensing Cycling of elements as saprophytes (Global N and C cycles) Remediating residual pesticides and atmospheric hydrocarbon pollutants Help in plant development and health as biofertilizers , phytostimulators and biopesticides to protect against invading pathogens ( Lugtenberg et al., 2002; Delmotte et al., 2009; Zhou et al ., 2011 ; Ali et al., 2012) Functions

29. Growth hormones Auxins Eg : IAA produced by Sphingomonas Cytokinins Brassinosteroids , Gibberellins, Abscisic acid , Ethylene, Jasmonates and Strigolactones

30. Pigments Sphinomonas Pantoea Clavibacter Sphingomonas – astaxanthins Methylobacterium - carotenoids ( Xanthophylls ) Clavibacterium – Xanthophylls Pantoea –carotenoid Xanthomonas – Xanthomonadin

31. UV Protection mechanisms 1. Methylobacterium , Sphingomonas , Pseudomonas etc., possess pigmentation 2. Special DNA repair mechanisms 3. Up regulation of stress response proteins ( Eg : PhaA ) 4. Production of extracellular polysaccharides

32. Pollinator Attractions

33. VOC’s “Volatile organic compounds (VOCs) are a large class of low-molecular-weight, carbon-containing compounds characterized by their high volatility, low vapor pressure (≥ 0.01 kPa at 20 ° C), and low water solubility” (Herrmann, 2010 ) To date, a total of 1700 volatile compounds have been isolated from more than 90 plant families. Plant volatiles constitute about 1 % of plant secondary metabolites and are mainly represented by terpenoids , phenylpropanoids / benzenoids , fatty acid derivatives , and amino acid derivatives . Volatile organic compounds (VOC) are organic chemicals that when released into the atmosphere can react with sunlight and nitrogen oxides ( NOx ) to form tropospheric (ground-level) ozone (Melanie et al., 2010 )

34. TMTT=trimethyltrideca‐1,3,7,11‐tetraene DMNT= homoterpenes , ( E )‐4,8‐dimethyl‐1,3,7‐nonatriene

35. Why we need to study about phyllosphere ? Improving our understanding about the behaviour of microorganisms in this habitat will facilitate biotechnological applications for protecting plants, Promoting plant growth, Avoid human pathogenic bacteria in plant food and, Phytoremediation of volatile pollutants from the air.

36. Research article

37. Tillandsia spp

38. Research article