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Title: A Transcriptional Program for Arbuscule Degeneration during AM Symbiosis Is Regulated by MYB1

Journal Article · · Current Biology

During the endosymbiosis formed between plants and arbuscular mycorrhizal (AM) fungi, the root cortical cells are colonized by branched hyphae called arbuscules, which function in nutrient exchange with the plant. Despite their positive function, arbuscules are ephemeral structures, and their development is followed by a degeneration phase, in which the arbuscule and surrounding periarbuscular membrane and matrix gradually disappear from the root cell. Currently, the root cell’s role in this process and the underlying regulatory mechanisms are unknown. Here, by using a Medicago truncatula pt4 mutant in which arbuscules degenerate prematurely, we identified arbuscule degeneration-associated genes, of which 38% are predicted to encode secreted hydrolases, suggesting a role in disassembly of the arbuscule and interface. Through RNAi and analysis of an insertion mutant, we identified a symbiosis-specific MYB-like transcription factor (MYB1) that suppresses arbuscule degeneration in mtpt4. In myb1, expression of several degeneration-associated genes is reduced. Conversely, in roots constitutively overexpressing MYB1, expression of degeneration-associated genes is increased and subsequent development of symbiosis is impaired. MYB1-regulated gene expression is enhanced by DELLA proteins and is dependent on NSP1, but not NSP2. Furthermore, MYB1 interacts with DELLA and NSP1. Our data identify a transcriptional program for arbuscule degeneration and reveal that its regulators include MYB1 in association with two transcriptional regulators, NSP1 and DELLA, both of which function in preceding phases of the symbiosis. Here we propose that the combinatorial use of transcription factors enables the sequential expression of transcriptional programs for arbuscule development and degeneration.

Research Organization:
Boyce Thompson Institute for Plant Research, Ithaca, NY (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
FG02-08ER64628; IOS-1353367; IOS-1127155; IOS-0820005; DBI-0618969; DE FG02-08ER64628
OSTI ID:
1434368
Alternate ID(s):
OSTI ID: 1416248; OSTI ID: 1533713
Journal Information:
Current Biology, Vol. 27, Issue 8; ISSN 0960-9822
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 73 works
Citation information provided by
Web of Science

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Cited By (3)

Comparative transcriptome analysis of Poncirus trifoliata identifies a core set of genes involved in arbuscular mycorrhizal symbiosis journal July 2018
The mycorrhiza-dependent defensin MtDefMd1 of Medicago truncatula acts during the late restructuring stages of arbusculecontaining cells text January 2018
Insights into the complex role of GRAS transcription factors in the arbuscular mycorrhiza symbiosis text January 2019