Interkingdom regulation of root development by plant hormone producing beneficial bacteria hos Institut for Plante- og Miljøvidenskab - Københavns Universitet

Summary:

Phytohormones like cytokinins (CKs) are chemical messengers that coordinates plants cells activity, play vital roles in many aspects of plants life including responses to abiotic stress. Microbes can alter plant root development and growth by producing plant growth–regulating substances including CKs. This project addresses the so far poorly understood mechanisms that govern the dual beneficial effects of beneficial root associated bacteria on plant development and physiology to confer drought tolerance. These functions are notably relevant for adaptation within climate change scenarios and also for sustainable and environmentally friendly agricultural production by their application as biostimulants to improve stress resilience and secure yield stability.

Background:

Culture independent metagenome sequencing revealed that plants are associated with a variable number and diversity of microbe. They are referred to as microbiota, and collectively encode the microbiome, the “second genome of a plant”. The versatile effects of plant beneficial bacteria (PBB) can be divided into two function: (1) Improvement of environmental adaptability, ecological plasticity and fitness and (2) support of plant and root growth, development and architecture. These functions are notably relevant for adaptation within climate change scenarios and also for sustainable and environmentally friendly agricultural production by their application as biostimulants to improve stress resilience and secure yield stability. Phytohormones like CKs are chemical messengers that coordinates plants cells activity, play vital roles in many aspects of plants life including responses to abiotic stress. Microbes can alter root development and growth by producing plant growth–regulating substances including auxin and CKs. This project addresses the so far poorly understood mechanisms that govern the dual beneficial effects of beneficial root associated bacteria on plant development and physiology

Concept and objectives:

This interdisciplinary project addresses the underexplored interkingdom signaling that governs the impact of prokaryotic CK production on the host plant root development and physiology for drought stress resilience. Based on literature data anda proof of concept the central hypothesis is derived: the ability of PBB Pfl G20-18 to modulate root architecture and physiology of barley depends on the ability to produce the plant hormone CK.

This project addresses the current knowledge gaps by following three specific objectives:

  1. Characterization of basic effects of PBB CKs on root architecture, holobiont physiology with a focus on source-sink relation and antioxidant metabolism and molecular signalling.
  2. Understanding the underlying molecular mechanism by a dual functional approach with both genetically modified plants and bacteria.
  3. Characterization of context dependency of basic effect of PBB CKs under special consideration of the impact of drought stress.

Experimental approaches:

E1. Effect of Pfl 20-18 produced CKs on root architecture and holobiont physiology. The impact of Pfl 20-18 CKs on barley, cv. Guld, will be compared with the CK deficient knockout mutants disrupted in the Pfl 20-18 CK biosynthetic gene miaA to characterize the impact of Pfl 20-18 CKs on barley growth, development, carbo-hydrate- antioxidant metabolism, assimilate partitioning, transcriptome, metabolome and hormones.

E2. Mechanistic interaction of Pfl 20-18 derived CKs with other hormones. The interaction between bacterial CK, ethylene and auxin production and their impact on root morphology of barley will be functionally addressed by co-inoculation of Pfl G20-18, P. putida GR12-2 (auxin producing) and P. putida UW4 (ACC deaminase). Wild type and mutant bacterial strains will be comparatively tested.

E3. Impact of Pfl 20-18 mediated root architecture on drought stress resilience. To test the functionality CK mediated resilience experiments will be performed by analyzing drought stress responses of barley which will include also bacterial consortia. This will determine the impact of Pfl 20-18 derived CKs on the level of barley resistance to different drought levels imposed at vegetative and reproductive growth phases.

Expected outcome, impacts and originality:

The results are expected to increase the knowledge about interkingdom signalling mechanisms between plants and PBB beyond CK. The outcomes will contribute to understand how PBB can steer plant intrinsic and extrinsic processes that support their sessile nature and help to grow and reproduce in changing abiotic factors. This is notably relevant for adaptation within climate change scenarios. They are also important for applications for sustainable and environmentally friendly agricultural production by their application as biostimulants to improve stress resilience and secure yield stability. This project will contribute to a better understanding of the context dependency of microbial solution to make their effects more robust across pedo-climatic conditions and thus contribute to the green transition.

The research group: Who are we?

Different aspects of the interaction of plants with beneficial microbes are a major research focus in the research group “Molecular Plant Physiology and Plant Phenomics”. See our home page, list of publications or press release press release.

Our lab is involved in different funded collaborative research project. Those include the the two EU international training networks, BestPass addressing microbial endophytes (https://bestpass.ku.dk/) and MiRA addressing microbe induced resistance against insect pests (https://mira.ku.dk/). In addtion, our lab is partner in the national project Bac4CroP to establish novel screening systems with funding from the Danish Innovation Fund and the big international Cooperative Crop Resiliency Program CCRP funded by the Novo Nordisk Foundation with ca. 30 mio Euro to spur the second green revolution

Video showing our research infrastructures

Growth facilities and phenomics research infrastructures

Within this general research topic specific BSc or MSc thesis project or projects outside course scope (POCS) can be tailed to specific particular topic and methodological interests. Please do not hesitate to contact Thomas via the online form or directly to arrange a phone, video or personal meeting to get further information and discuss your own ideas questions.

Thomas Roitsch

Roitsch@plen.ku.dk

Tel. 35 33 15 26

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