Cytokinin induction of root nodule primordia in Lotus japonicus is regulated by a mechanism operating in the root cortex

Anne Birgitte Heckmann; Niels Sandal; Anita Søndergaard Bek; Lene H Madsen; Anna Jurkiewicz; Mette Wibroe Nielsen; Leila Tirichine; Jens Stougaard

doi:10.1094/MPMI-05-11-0142

Cytokinin induction of root nodule primordia in Lotus japonicus is regulated by a mechanism operating in the root cortex

Anne Birgitte Heckmann, Niels Sandal, Anita Søndergaard Bek, Lene H Madsen, Anna Jurkiewicz, Mette Wibroe Nielsen, Leila Tirichine, Jens Stougaard

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

144 Citations (Scopus)

Abstract

Cytokinin plays a central role in the formation of nitrogen-fixing root nodules following inoculation with rhizobia. We show that exogenous cytokinin induces formation of discrete and easily visible nodule primordia in Lotus japonicus roots. The expression of nodulin genes was up-regulated upon cytokinin treatment, suggesting that the genuine nodulation program was indeed activated. This offers a simple approach for dissecting the underlying mechanism. Cytokinin-induced nodule primordia formation was unperturbed in several loss-of-function mutants impaired in epidermal responses to rhizobial infection and/or Nod factor application. However, absence of primordia in nsp1, nsp2 and nin mutants showed the requirement for these transcriptional regulators in the cytokinin-mediated activation of the root cortex. Distinguishing the epidermal and cortical responses further, we found that external cytokinin application induced expression of the Nin::GUS reporter gene within the root cortex but not in the root epidermis. Using L. japonicus hit1 and har1 mutants, we demonstrate that discrete activation of root cortical cells by cytokinin depends on the LHK1 cytokinin receptor and is subjected to HAR1-mediated autoregulation.

Original language	English
Journal	Molecular plant-microbe interactions
Volume	24
Issue	11
Pages (from-to)	1385-1395
ISSN	0894-0282
DOIs	https://doi.org/10.1094/MPMI-05-11-0142
Publication status	Published - 19 Jul 2011

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@article{c9dfb156846d4dd7834edefa644d1bd1,

title = "Cytokinin induction of root nodule primordia in Lotus japonicus is regulated by a mechanism operating in the root cortex",

abstract = "Cytokinin plays a central role in the formation of nitrogen-fixing root nodules following inoculation with rhizobia. We show that exogenous cytokinin induces formation of discrete and easily visible nodule primordia in Lotus japonicus roots. The expression of nodulin genes was up-regulated upon cytokinin treatment, suggesting that the genuine nodulation program was indeed activated. This offers a simple approach for dissecting the underlying mechanism. Cytokinin-induced nodule primordia formation was unperturbed in several loss-of-function mutants impaired in epidermal responses to rhizobial infection and/or Nod factor application. However, absence of primordia in nsp1, nsp2 and nin mutants showed the requirement for these transcriptional regulators in the cytokinin-mediated activation of the root cortex. Distinguishing the epidermal and cortical responses further, we found that external cytokinin application induced expression of the Nin::GUS reporter gene within the root cortex but not in the root epidermis. Using L. japonicus hit1 and har1 mutants, we demonstrate that discrete activation of root cortical cells by cytokinin depends on the LHK1 cytokinin receptor and is subjected to HAR1-mediated autoregulation.",

author = "Heckmann, \{Anne Birgitte\} and Niels Sandal and Bek, \{Anita S{\o}ndergaard\} and Madsen, \{Lene H\} and Anna Jurkiewicz and Nielsen, \{Mette Wibroe\} and Leila Tirichine and Jens Stougaard",

year = "2011",

month = jul,

day = "19",

doi = "10.1094/MPMI-05-11-0142",

language = "English",

volume = "24",

pages = "1385--1395",

journal = "Molecular plant-microbe interactions",

issn = "0894-0282",

publisher = "American Phytopathological Society",

number = "11",

}

Cytokinin induction of root nodule primordia in Lotus japonicus is regulated by a mechanism operating in the root cortex. / Heckmann, Anne Birgitte; Sandal, Niels; Bek, Anita Søndergaard et al.
In: Molecular plant-microbe interactions, Vol. 24, No. 11, 19.07.2011, p. 1385-1395.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Cytokinin induction of root nodule primordia in Lotus japonicus is regulated by a mechanism operating in the root cortex

AU - Heckmann, Anne Birgitte

AU - Sandal, Niels

AU - Bek, Anita Søndergaard

AU - Madsen, Lene H

AU - Jurkiewicz, Anna

AU - Nielsen, Mette Wibroe

AU - Tirichine, Leila

AU - Stougaard, Jens

PY - 2011/7/19

Y1 - 2011/7/19

N2 - Cytokinin plays a central role in the formation of nitrogen-fixing root nodules following inoculation with rhizobia. We show that exogenous cytokinin induces formation of discrete and easily visible nodule primordia in Lotus japonicus roots. The expression of nodulin genes was up-regulated upon cytokinin treatment, suggesting that the genuine nodulation program was indeed activated. This offers a simple approach for dissecting the underlying mechanism. Cytokinin-induced nodule primordia formation was unperturbed in several loss-of-function mutants impaired in epidermal responses to rhizobial infection and/or Nod factor application. However, absence of primordia in nsp1, nsp2 and nin mutants showed the requirement for these transcriptional regulators in the cytokinin-mediated activation of the root cortex. Distinguishing the epidermal and cortical responses further, we found that external cytokinin application induced expression of the Nin::GUS reporter gene within the root cortex but not in the root epidermis. Using L. japonicus hit1 and har1 mutants, we demonstrate that discrete activation of root cortical cells by cytokinin depends on the LHK1 cytokinin receptor and is subjected to HAR1-mediated autoregulation.

AB - Cytokinin plays a central role in the formation of nitrogen-fixing root nodules following inoculation with rhizobia. We show that exogenous cytokinin induces formation of discrete and easily visible nodule primordia in Lotus japonicus roots. The expression of nodulin genes was up-regulated upon cytokinin treatment, suggesting that the genuine nodulation program was indeed activated. This offers a simple approach for dissecting the underlying mechanism. Cytokinin-induced nodule primordia formation was unperturbed in several loss-of-function mutants impaired in epidermal responses to rhizobial infection and/or Nod factor application. However, absence of primordia in nsp1, nsp2 and nin mutants showed the requirement for these transcriptional regulators in the cytokinin-mediated activation of the root cortex. Distinguishing the epidermal and cortical responses further, we found that external cytokinin application induced expression of the Nin::GUS reporter gene within the root cortex but not in the root epidermis. Using L. japonicus hit1 and har1 mutants, we demonstrate that discrete activation of root cortical cells by cytokinin depends on the LHK1 cytokinin receptor and is subjected to HAR1-mediated autoregulation.

U2 - 10.1094/MPMI-05-11-0142

DO - 10.1094/MPMI-05-11-0142

M3 - Journal article

C2 - 21770769

SN - 0894-0282

VL - 24

SP - 1385

EP - 1395

JO - Molecular plant-microbe interactions

JF - Molecular plant-microbe interactions

IS - 11

ER -

Cytokinin induction of root nodule primordia in Lotus japonicus is regulated by a mechanism operating in the root cortex

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