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  • Mutation of BAM2 rescues the sunn hypernodulation phenotype in Medicago truncatula, suggesting that a signaling pathway like CLV1/BAM in Arabidopsis affects nodule number
Title: Mutation of BAM2 rescues the sunn hypernodulation phenotype in Medicago truncatula, suggesting that a signaling pathway like CLV1/BAM in Arabidopsis affects nodule number
The unique evolutionary adaptation of legumes for nitrogen-fixing symbiosis leading to nodulation is tightly regulated by the host plant. The autoregulation of nodulation (AON) pathway negatively regulates the number of nodules formed in response to the carbon/nitrogen metabolic status of the shoot and root by long-distance signaling to and from the shoot and root. Central to AON signaling in the shoots ofMedicago truncatulais SUNN, a leucine-rich repeat receptor-like kinase with high sequence similarity with CLAVATA1 (CLV1), part of a class of receptors inArabidopsisinvolved in regulating stem cell populations in the root and shoot. This class of receptors inArabidopsisincludes the BARELY ANY MERISTEM family, which, like CLV1, binds to CLE peptides and interacts with CLV1 to regulate meristem development.M. truncatulacontains five members of theBAMfamily, but onlyMtBAM1andMtBAM2are highly expressed in the nodules 48 hours after inoculation. Plants carry mutations in individualMtBAMs, and several doubleBAMmutant combinations all displayed wild-type nodule number phenotypes. However,Mtbam2suppressed thesunn-5hypernodulation phenotype and partially rescued the short root length phenotype ofsunn-5 when present in asunn-5background. Grafting determined thatbam2suppresses supernodulation from the roots, regardless of theSUNNstatus of the root. Overexpression ofMtBAM2in wild-type plants increases nodule numbers, while overexpression ofMtBAM2in somesunnmutants rescues the hypernodulation phenotype, but not the hypernodulation phenotypes of AON mutantrdn1-2orcrn. Relative expression measurements of the nodule transcription factor MtWOX5 downstream of the putativebam2 sunn-5complex revealed disruption of meristem signaling; while bothbam2andbam2 sunn-5influenceMtWOX5expression, the expression changes are in different directions. We propose a genetic model wherein the specific root interactions of BAM2/SUNN are critical for signaling in nodule meristem cell homeostasis inM. truncatula.  more » « less
Award ID(s):
2139351
PAR ID:
10535907
Author(s) / Creator(s):
;
Publisher / Repository:
Frontiers Media SA
Date Published:
Journal Name:
Frontiers in Plant Science
Volume:
14
ISSN:
1664-462X
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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