Skip to main content

ORIGINAL RESEARCH article

Front. Plant Sci.
Sec. Plant Symbiotic Interactions
Volume 15 - 2024 | doi: 10.3389/fpls.2024.1504404

TML1 AND TML2 SYNERGISTICALLY REGULATE NODULATION AND AFFECT ARBUSCULAR MYCORRHIZA IN MEDICAGO TRUNCATULA

Provisionally accepted
Diptee Chaulagain Diptee Chaulagain 1,2Elise Schnabel Elise Schnabel 1,3Mikayla Kappes Mikayla Kappes 4Erica Xinlei Lin Erica Xinlei Lin 5Lena Maria Müller Lena Maria Müller 4Julia Alice Frugoli Julia Alice Frugoli 1*
  • 1 Department of Genetics and Biochemistry, Clemson University, Clemson, United States
  • 2 Department of Bioengineering, College of Engineering, Computing and Applied Science, Clemson University, Clemson, South Carolina, United States
  • 3 Department of Plant and Environmental Sciences, College of Agriculture, Forestry and Life Sciences, Clemson University, Clemson, South Carolina, United States
  • 4 Plant Molecular and Cellular Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, United States
  • 5 Department of Biology, University of Miami, Coral Gables, FL, United States

The final, formatted version of the article will be published soon.

    Two symbiotic processes, nodulation and arbuscular mycorrhiza, are primarily controlled by the plant's need for nitrogen (N) and phosphorus (P), respectively. Autoregulation of Nodulation (AON) and Autoregulation of Mycorrhization (AOM) both negatively regulate their respective processes and share multiple components -plants that make too many nodules usually have higher AM fungal root colonization. The protein TML (TOO MUCH LOVE) was shown to function in roots to maintain susceptibly to rhizobial infection under low N conditions and control nodule number through AON in Lotus japonicus. M. truncatula has two sequence homologs: MtTML1 and MtTML2. We report the generation of stable single and double mutants harboring multiple allelic variations in MtTML1 and MtTML2 using CRISPR-Cas9 targeted mutagenesis and screening of a transposon mutagenesis library. Plants containing single mutations in MtTML1 or MtTML2 produced 2-3 times the nodules of wild-type plants whereas plants containing mutations in both genes displayed a synergistic effect, forming 20x more nodules compared to wild type plants. Examination of expression and heterozygote effects suggest genetic compensation may play a role in the observed synergy. Plants with mutations in both TMLs only showed mild increases in AM fungal root colonization at later timepoints in our experiments, suggesting these genes may also play a minor role in AM symbiosis regulation. The mutants created will be useful tools to dissect the mechanism of synergistic action of MtTML1 and MtTML2 in M. truncatula symbiosis with beneficial microbes.

    Keywords: nodulation, Mycorrhization, Medicago truncatula, AON, AOM, TML

    Received: 30 Sep 2024; Accepted: 11 Nov 2024.

    Copyright: © 2024 Chaulagain, Schnabel, Kappes, Lin, Müller and Frugoli. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Julia Alice Frugoli, Department of Genetics and Biochemistry, Clemson University, Clemson, United States

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.