1. James White Rutgers University jwhite3728@gmail.com
Leaf-Base Symbiosis (LBS): a new class of bacterium-fungus-plant symbiosis
James White
Rutgers University

2. Desert habitat

3. Coronado National Forest

4. Agave palmeri

5. Agave desertii in rocks

6. Agave palmeri on rocks

7. Agave roots

8. Giant Agave

9. Giant Agave leaf bases

10. Agave leaves-DAB stained to show Development of LBS (left)

11. Agave palmeri—LBS development

12. Agave palmeri-development of LBS

13. Agave leaf bases with microbial layers

14. Agave palmeri leaf bases with LBS

15. Soil accumulation on LBS

16. Yucca elata

17. Yucca leaf bases

18. Survey for LBS in Desert and Tropical Sites
Plant Genus (Family)
Panamanian Tropical Forest (% w LBS); > 250 cm H20/year
Sonoran Desert (% w LBS); < 12.5 cm H2O/year
Agave (Agavoideae)
0 (n=20)
83 (n=30)
Yucca (Agavoideae)
0 (n=23)
100 (n=25)
Calibanus (Agavoideae) --
100 (n=3)
Dasilyron (Agavoideae)
80 (n=10)
Pandanus (Pandanaceae)
0 (n=11)

19. Agave palmeri—showing sclerenchyma layer on epidermis

20. Agave palmeri-LBS-fungal layer

21. Agave palmeri-LBS-bacterial layer

22. Agave palmeri—LBS formation

23. Agave palmeri—Epicoccum sp.

24. Agave-fungal-bacterial symbiosis (bacteria entering hypha)

26. Fusion of bacteria

27. Bacteroid with wall
Fusion

28. Intact epidermis on adaxial leaf sheath

29. Epidermis at LBS

30. Epidermis at LBS

31. Section of LBS showing bacterial layer

32. Bacterial Layer
Fungal hyphae in
Epidermis

33. Bacterial layer above fungal layer

35. Proposed roles of mutualists
Bacterium functions in nitrogen fixation
Fungus functions in translocation to plant and vector for bacterium
Hypothetical benefits to host in oxidative stress tolerance (effects of auxins and ros secretion by endophytes)

36. Is this association found in other plants?
Other desert plants?
Other plants with a similar sheathing leaf habit?

37. Agave schottii

38. Agave schottii

39. Agave schottii

40. Calibanus hookeri (Nolinaceae)

41. Calibanus hookeri

42. Calibanus hookeri

43. Yucca

44. Yucca schottii

45. Yucca elata

46. Yucca schottii

49. Yucca--sclerified cells under LBS

50. Schlerenchyma—with pit connections (may be porous to nutrients but resistant to microbial passage)

51. Yucca elata—bacterial clusters in matrix layer (crystal violet stain)

54. Yucca elata—fungus and bacteria on LBS

55. Yucca elata—LBS (showing hyphae and bacteria)

56. Yucca schottii-soil accumulation

57. Yucca elata—with age the LBS is a ‘plant rumen’ with a mix of microbes

58. Dasylirion wheeleri-sotol

59. Dasylirion wheeleri leaf bases

60. Sotol plant

61. Sotol Leaf Bases

62. Seed transmitted bacterium identified as Klebsiella oxytoca

63. Palms

64. Palm

65. Palm leaf bases

66. Palm leaf bases

67. Palm leaf base showing microbial layer

68. Palm trunk showing microbial layer

69. Palm leaf base with microbial layer

70. Palm trunk

71. Palm trunk adapted for microbial activity in trunk

72. Palm trunks

73. Bromeliads

74. Bromeliad leaf base with microbial layer

75. Is it important to understand what these endophytes and epiphytes are doing in plants?
Economic arguments
Basic science arguments

76. Agave plants die after flowering

77. Agave-leaf bases

78. Agave leaf epiphyllous mycelium on leaf base

79. Agave-endophytic mycelium in the epiphyllous mycelium zone

80. Agave-epiphyllous and endophytic mycelium

81. Early development of LBS—microbes appear in stomata

82. Agave desertii-early development of LBS

83. Fusarium sp.

86. Endophytic Hypha in Mesophyll

87. Endophytic Hyphae in Leaf Sheath Mesophyll

88. Bacterium isolated from fungus

89. Bacterium: gram negative rods

90. Fungus: Plectosporium?

93. What is needed?
Evaluate absorption into plants of nutrients from leaf bases
Assess source of nutrients at leaf bases
Determine importance of nutrients from leaf bases vs from soils
Determine the functions of microbes involved in leaf base symbioses.