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3333654 
Journal Article 
DELLA proteins regulate arbuscule formation in arbuscular mycorrhizal symbiosis 
Floss, DS; Levy, JG; Levesque-Tremblay, V; Pumplin, N; Harrison, MJ 
2013 
1 
Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
EISSN: 1091-6490 
110 
51 
E5025-E5034 
WOS:000328548600014 
Most flowering plants are able to form endosymbioses with arbuscular mycorrhizal fungi. In this mutualistic association, the fungus colonizes the root cortex and establishes elaborately branched hyphae, called arbuscules, within the cortical cells. Arbuscule development requires the cellular reorganization of both symbionts, and the resulting symbiotic interface functions in nutrient exchange. A plant symbiosis signaling pathway controls the development of the symbiosis. Several components of the pathway have been identified, but transcriptional regulators that control downstream pathways for arbuscule formation are still unknown. Here we show that DELLA proteins, which are repressors of gibberellic acid (GA) signaling and function at the nexus of several signaling pathways, are required for arbuscule formation. Arbuscule formation is severely impaired in a Medicago truncatula Mtdella1/Mtdella2 double mutant; GA treatment of wild-type roots phenocopies the della double mutant, and a dominant DELLA protein (della1-Delta 18) enables arbuscule formation in the presence of GA. Ectopic expression of della1-Delta 18 suggests that DELLA activity in the vascular tissue and endodermis is sufficient to enable arbuscule formation in the inner cortical cells. In addition, expression of della1-Delta 18 restores arbuscule formation in the symbiosis signaling pathway mutant cyclops/ipd3, indicating an intersection between DELLA and symbiosis signaling for arbuscule formation. GA signaling also influences arbuscule formation in monocots, and a Green Revolution wheat variety carrying dominant DELLA alleles shows enhanced colonization but a limited growth response to arbuscular mycorrhizal symbiosis. 
endosymbiosis; phytohormone; biotrophic; cyclops; Lotus japonicus