After late spring teaching and the summer break, the presidential blog is back!
Not all biotechnology is about genetic engineering or gene editing. In the broad sense, biological control is also biotechnology: using biological processes for a technological purpose, i.e., to control diseases. I will explore what we know about the biology of a group of organisms that can be used to control disease, namely endophytes.
The plant is really a holobiont: a community of organisms, where the sum is greater than the parts. As pathologists, we focus on the destructive things that pathogens do since society needs us to try and ensure food security and other services. In a recent current opinions piece [1], we looked at other ways that fungi (as our model pathogens) can interact with plants, from within. We observed how constituents of the endobiome of healthy plants can include potentially harmful pathogens of the host, and that these could cause disease when inoculated into fresh hosts in the absence of other members of their endobiome [2].
Indeed, it is something of an enigma that endophytes can invoke an active defence in plants but survive it [3, 4]. Of course, the question that then arises is: whether they would do better if they avoided inducing any defences? This has been seen with pathogens where repression of selected host defence genes resulted in increased levels of infection. It should be possible to design a series of elegant studies to look at the same phenomenon for endophytes; by repressing some of the same the defences using molecular genetic tools (e.g., gene editing). Would that result in a greater biomass of endophyte? Is the endophyte biomass at a level where they avoid being arrested by activated immune responses? How much endophyte biomass can a plant tolerate before amensalism sets in [5]? We still know remarkably little about these aspects of fungal communities and their interactions with plants.
How can we perhaps exploit this knowledge?
Do endophytes have an enhanced potential for being developed as biological control of plant disease that differs from other microbes? There is no generic answer to this question, but our instinct tells us that an endophyte established within host tissues is less likely to be subject to external environmental factors than an epiphyte sitting on the surface of the plant. This encourages us. How do we select endophytes for their potential? One approach is to look for organisms present in asymptomatic tissues in a crop subjected to high disease pressure [6, 7]. The argument is that the lack of symptoms reflects suppression of the pathogen by the endophyte. This approach offers the further advantage that the endophyte is established under the cultivation conditions and therefore potentially overcomes one of the main problems of biological control efficacy under real life conditions where environment, especially weather, is important for establishment and survival. There are several promising examples [6, 8-10] from different pathosystems.
Endophytes represent an exciting area with interesting biological questions and promising applications. Speakers at BSPP 2022 will address some of these issues.
References:
- Collinge DB, Jensen B and Jørgensen HJL (2022) Fungal endophytes in plants and their relationship to plant disease. Current Opinion in Microbiology 69:102177. doi.org/10.1016/j.mib.2022.102177
- Manzotti A, Bergna A, Burow M, Jørgensen HJL, Cernava T, Berg G, Collinge DB and Jensen B (2020) Insights into the community structure and lifestyle of the fungal root endophytes of tomato by combining amplicon sequencing and isolation approaches with phytohormone profiling. FEMS Microbiology Ecology 96. doi: 10.1093/femsec/fiaa052
- Rojas EC, Jensen B, Jørgensen HJL, Latz MAC, Esteban P and Collinge DB (2022) The Fungal Endophyte Penicillium olsonii ML37 Reduces Fusarium Head Blight by Local Induced Resistance in Wheat Spikes. Journal of Fungi 8:345.
- Ntana F, Johnson SR, Hamberger B, Jensen B, Jørgensen HJL and Collinge DB (2022) Regulation of tomato specialised metabolism after establishment of symbiosis with the endophytic fungus Serendipita indica. Microorganisms 10:194. doi: 10.3390/microorganisms10010194
- Jørgensen HJL, Collinge DB, Rojas EC, Latz MAC, Manzotti A, Ntana F and Jensen B (2020) Plant endophytes. Encyclopaedia of Life Sciences. doi: 10.1002/9780470015902.a0028893
- Collinge DB, Jørgensen HJL, Latz MAC, Manzotti A, Ntana F, Rojas EC and Jensen B (2019) Searching for novel fungal biological control agents for plant disease control among endophytes. In: Hodkinson TR, Doohan FM, Saunders M and Murphy BR (eds) Endophytes: for a growing world Cambridge University Press, Cambridge pp. 25-51
- Köhl J, Postma J, Nicot P, Ruocco M and Blum B (2011) Stepwise screening of microorganisms for commercial use in biological control of plant-pathogenic fungi and bacteria. Biological Control 57:1-12. doi: https://doi.org/10.1016/j.biocontrol.2010.12.004
- Köhl J, Scheer C, Holb IJ, Masny S and Molhoek W (2015) Toward an integrated use of biological control by Cladosporium cladosporioides H39 in apple scab (Venturia inaequalis) management. Plant Disease 99:535-543. doi: 10.1094/pdis-08-14-0836-re
- Latz MAC, Jensen B, Collinge DB and Jørgensen HJL (2020) Identification of two endophytic fungi that control Septoria tritici blotch in the field, using a structured screening approach. Biological Control 141:104128. doi: https://doi.org/10.1016/j.biocontrol.2019.104128
- Rojas EC, Jensen B, Jørgensen HJL, Latz MAC, Esteban P, Ding Y and Collinge DB (2020) Selection of fungal endophytes with biocontrol potential against Fusarium head blight in wheat. Biological Control 144:104222. doi: https://doi.org/10.1016/j.biocontrol.2020.104222
TITLE IMAGE: All images used with permission of the author.
