Universität zu Köln

Kürtös, Noah (2024). Nitrogen signaling in the mature endodermis of Arabidopsis and its role in microbe-elicited soil nitrogen utilization. PhD thesis, Universität zu Köln.

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Abstract

Nitrogen is a key component to life. The bioavailability of nitrogen (N), in the form of ammonium (NH4+) and nitrate (NO3-), in soil ecosystem varies strongly and it often is a growth limiting factor for plants. Therefore, plants have evolved an arsenal of nitrogen signalling and uptake mechanisms to forage nitrogen from their environment. Once taken up by the root, nitrogen amongst other nutrients, is transported to other organs of the plant through the central vascular cylinder. To prevent the leakage of nutrients out of the vasculature, it is surrounded by a barrier tissue: the endodermis. We have only recently started to understand how the reinforcement of endodermal cell walls by lignin and suberin is coordinated with the plant nutrient status and especially the role of nitrogen remained unresolved. Here we found that, in Arabidopsis thaliana, nitrogen starvation leads to an increase of endodermal suberization and that endodermal nitrogen signalling and suberization are required to facilitate microbe-dependent growth promotion after nitrogen fertilizer application to agricultural soil. Tissue-specific post-transcriptional analysis of nitrogen starved plants revealed, that in the mature primary root, the high affinity nitrate transporter NRT2.1 and the high affinity ammonium transporter AMT1.5 are upregulated in the outer cortex layer above the suberized endodermis. Similarly, coumarin biosynthesis appears to be distinctively regulated in the mature root under nitrogen starvation. The scopoletin synthesizing gene F6’H1 and the fraxetin synthesizing gene S8H are upregulated in the mature cortex, while the sideretin synthesizing gene CYP82C4 is downregulated. Moreover, the nitrate transceptor NPF6.3 and the transcription factor NIGT1.3 are upregulated specifically in the endodermis of nitrogen starved plants. Manipulation of nitrogen signalling by overexpressing the nitrate responsive transcription factor NLP7, in the endodermis specifically, leads to higher sensitivity to nitrate and resulted in a reduction of suberization under nitrate re-supply. When grown in nitrogen-fertilized natural soil NLP7 overexpression leads to a loss of microbe-dependent growth promotion. Similarly, the f6’h1 mutant, which is unable to produce coumarins, is unable to benefit from nitrogen fertilization. Our results demonstrate that the endodermis, likely through NPF6.3 and NIGT1.3, plays a central role in coordinating plant nitrogen homeostasis. The distinct modulation of the root microbiome, through secreted secondary metabolites, has gained recent attention. It appears to be an integral tool for the adaption of plants to nutrient limiting conditions. How plant-microbial relationships are established and communicated across a closed endodermal barrier will be a key question of upcoming research.

Item Type:	Thesis (PhD thesis)
Translated title:	Title Language Stickstoffsignaltransduktion in der reifen Endodermis von Arabidopsis thaliana und deren Rolle bei der mikrobenvermittelten Nutzung von Stickstoffdünger German
Creators:	Creators Email ORCID ORCID Put Code Kürtös, Noah n.kuertoes@gmail.com UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-720936
Date:	2024
Publisher:	Universität Köln
Place of Publication:	KUPS
Language:	English
Faculty:	Collaborative Research Centers
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Plant Breeding Research
Subjects:	Data processing Computer science Natural sciences and mathematics Earth sciences Life sciences Agriculture
Uncontrolled Keywords:	Keywords Language Nitrogen English Plant science English Nutrient uptake English Molecular Biology English RNAseq English TRAPseq English Microbiome English Agriculture English Soil English UNSPECIFIED English UNSPECIFIED English
Date of oral exam:	5 December 2023
Referee:	Name Academic Title Schulze-Lefert, Paul Prof. Dr. Kopriva, Stanislav Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/72093