Skip to main content

Advertisement

Log in

Lotus japonicus HAR1 regulates root morphology locally and systemically under a moderate nitrate condition in the absence of rhizobia

  • Original Article
  • Published:
Planta Aims and scope Submit manuscript

Abstract

Main conclusion

The local and long-distance signaling pathways mediated by the leucine-rich repeat receptor kinase HAR1 suppress root branching and promote primary root length in response to nitrate supply.

Abstract

The root morphology of higher plants changes plastically to effectively absorb nutrients and water from the soil. In particular, legumes develop root organ nodules, in which symbiotic rhizobia fix atmospheric nitrogen in nitrogen-poor environments. The number of nodules formed in roots is negatively regulated by a long-distance signaling pathway that travels through shoots called autoregulation of nodulation (AON). In the model plant Lotus japonicus, defects in AON genes, such as a leucine-rich repeat receptor kinase HYPERNODULATION ABERRANT ROOT FORMATION 1 (HAR1), an orthologue of CLAVATA1, and the F-box protein TOO MUCH LOVE (TML), induce the formation of an excess number of nodules. The loss-of-function mutant of HAR1 exhibits a short and bushy root phenotype in the absence of rhizobia. We show that the har1 mutant exhibits high nitrate sensitivity during root development. The uninfected har1 mutant significantly increased lateral root number and reduced primary root length in the presence of 3 mM nitrate, compared with the wild-type and tml mutant. Grafting experiments indicated that local and long-distance signaling pathways via root- and shoot-acting HAR1 additively regulated root morphology under the moderate nitrate concentrations. These findings allow us to propose that HAR1-mediated signaling pathways control the root system architecture by suppressing lateral root branching and promoting primary root elongation in response to nitrate availability.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3
Fig. 4

Similar content being viewed by others

Data availability statement

The data that support the findings of this study are available from the corresponding author, MK, upon reasonable request.

Abbreviations

AON:

Autoregulation of nodulation

CLE:

CLAVATA 3 (CLV3)/EMBRYO SURROUNDING REGION-related

CLV:

CLAVATA

LR:

Lateral root

LRR-RK:

Leucine-rich repeat receptor kinase

N:

Nitrogen

PR:

Primary root

RSA:

Root system architecture

TML:

TOO MUCH LOVE

References

Download references

Acknowledgements

We thank Dr. Nao Okuma for helpful technical advice on the grafting experiment and qRT-PCR analysis. This work was supported by JSPS KAKENHI (17H03702, 20H03283) to MK.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Masayoshi Kawaguchi.

Ethics declarations

Conflict of interest

The authors declare that there are no conflicts of interest.

Additional information

Communicated by Dorothea Bartels.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary file1 (PDF 147 KB)

Fig. S1

Effects of nitrate supply on root morphology in WT, har1 and tml plants. a Primary root length (PRL). b Total lateral root (LR) number per plant. Numbers of first (c) and second (d) LRs. e Total LR length (LRL) per plant. Plants were grown in 0.03, 0.3, 3, or 30 mM nitrate for 12 days (n = 10 plants). Boxplots show the median (thick line), quartiles (box), minimum and maximum ranges (lines), and outliers (circles). Different letters represent significant differences across nitrate concentrations and plant genotypes (one-way ANOVA, post hoc Tukey’s test, P < 0.05). Fig. S2 Effects of nitrate supply on the expression of AON-related genes. Gene expression levels of CLE-RS2 (a), TML (b), and HAR1 (c) in shoots and roots of WT plants grown in 0.03, 0.3, 3, or 30 mM nitrate for 12 days. ubiquitin (UBQ) was used as a reference gene. Different letters represent significant differences across plant genotypes (one-way ANOVA, post hoc Tukey’s test, P < 0.05). Error bars indicate ± SE from three biological replicates (PPTX 118 KB)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hayashi-Tsugane, M., Kawaguchi, M. Lotus japonicus HAR1 regulates root morphology locally and systemically under a moderate nitrate condition in the absence of rhizobia. Planta 255, 95 (2022). https://doi.org/10.1007/s00425-022-03873-8

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1007/s00425-022-03873-8

Keywords

Navigation