James White Rutgers University jwhite3728@gmail.com Leaf-Base Symbiosis (LBS): a new class of bacterium-fungus-plant symbiosis James White Rutgers University jwhite3728@gmail.com
Desert habitat
Coronado National Forest
Agave palmeri
Agave desertii in rocks
Agave palmeri on rocks
Agave roots
Giant Agave
Giant Agave leaf bases
Agave leaves-DAB stained to show Development of LBS (left)
Agave palmeri—LBS development
Agave palmeri-development of LBS
Agave leaf bases with microbial layers
Agave palmeri leaf bases with LBS
Soil accumulation on LBS
Yucca elata
Yucca leaf bases
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)
Agave palmeri—showing sclerenchyma layer on epidermis
Agave palmeri-LBS-fungal layer
Agave palmeri-LBS-bacterial layer
Agave palmeri—LBS formation
Agave palmeri—Epicoccum sp.
Agave-fungal-bacterial symbiosis (bacteria entering hypha)
Fusion of bacteria
Bacteroid with wall Fusion
Intact epidermis on adaxial leaf sheath
Epidermis at LBS
Epidermis at LBS
Section of LBS showing bacterial layer
Bacterial Layer Fungal hyphae in Epidermis
Bacterial layer above fungal layer
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)
Is this association found in other plants? Other desert plants? Other plants with a similar sheathing leaf habit?
Agave schottii
Agave schottii
Agave schottii
Calibanus hookeri (Nolinaceae)
Calibanus hookeri
Calibanus hookeri
Yucca
Yucca schottii
Yucca elata
Yucca schottii
Yucca--sclerified cells under LBS
Schlerenchyma—with pit connections (may be porous to nutrients but resistant to microbial passage)
Yucca elata—bacterial clusters in matrix layer (crystal violet stain)
Yucca elata—fungus and bacteria on LBS
Yucca elata—LBS (showing hyphae and bacteria)
Yucca schottii-soil accumulation
Yucca elata—with age the LBS is a ‘plant rumen’ with a mix of microbes
Dasylirion wheeleri-sotol
Dasylirion wheeleri leaf bases
Sotol plant
Sotol Leaf Bases
Seed transmitted bacterium identified as Klebsiella oxytoca
Palms
Palm
Palm leaf bases
Palm leaf bases
Palm leaf base showing microbial layer
Palm trunk showing microbial layer
Palm leaf base with microbial layer
Palm trunk
Palm trunk adapted for microbial activity in trunk
Palm trunks
Bromeliads
Bromeliad leaf base with microbial layer
Is it important to understand what these endophytes and epiphytes are doing in plants? Economic arguments Basic science arguments
Agave plants die after flowering
Agave-leaf bases
Agave leaf epiphyllous mycelium on leaf base
Agave-endophytic mycelium in the epiphyllous mycelium zone
Agave-epiphyllous and endophytic mycelium
Early development of LBS—microbes appear in stomata
Agave desertii-early development of LBS
Fusarium sp.
Endophytic Hypha in Mesophyll
Endophytic Hyphae in Leaf Sheath Mesophyll
Bacterium isolated from fungus
Bacterium: gram negative rods
Fungus: Plectosporium?
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.