ARS | Publication request: ENDOSYMBIOTIC FUNGI STRUCTUALLY INTEGRATED WITH LEAVES REVEALS A LICHENOUS CONDITION OF C4 GRASSES

Submitted to: In Vitro Cellular and Developmental Biology - Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 2006
Publication Date: March 11, 2007
Citation: Barrow, J.R., Lucero, M.E., Reyes-Vera, I., Havstad, K.M. 2007. Endosymbiotic fungi structually integrated with leaves reveals a lichenous condition of C4 grasses. In Vitro Cellular and Developmental Biology - Plants. 43:65-70.

Interpretive Summary: Vascular plants are generally assumed to be composed of pure and discrete plant cells and tissues. We have shown by specific staining, light and electron microscopy that the leaf anatomy of black grama, an important range grass of southwestern US rangelands is composed of plant and fungus cells. Two celled leaf structures, previously thought to be plant cells and used to distinguish between species of warm season grasses were in reality found to be fungal cells. This important native range grass is a composite plant-fungus organism, similar to lichens. The long ignored structural integration of fungal cells within plant tissues must be considered in describing plant anatomy, taxonomy, physiology and ecology of plants.

Technical Abstract: This paper addresses the assumed autonomy of vascular plants by revealing the presence of an obligate fungus structurally integrated with leaf anatomy of C4 grasses. We examined leaf surfaces of 26 species representing 14 genera of C4 grasses. In all species, we found similarities between leaf surface microhair-like structures and Uredomycete teliospores. These bicellular structures produced hyphae and spores, confirming they were fungal, rather than plant tissue. The plant-fungus structural morphology was also observed in Bouteloua eriopoda plants regenerated from embryonic meristem cells. The conserved symbiosis between fungi and C4 grasses suggests a lichenous association with evolutionary significance. The structural integration of endosymbiotic fungi with cells and tissues offers novel and unexplored approaches to developing physiological, ecological and systematic models of C4 grasses.