Plants, pathogens, poisoned vesicles

18 Dec 2017 - By: Jonathan Ingram

Plants, pathogens, poisoned vesicles

Extracellular vesicles image
Potential routes taken by extracellular vesicles, explained in detail in the Insight article by Petra Boevink. Open Access, see https://creativecommons.org/licenses/by/4.0/)



By Jonathan Ingram, Journal of Experimental Botany

The commonplace is the pathogen killing the plant. The opposite would be the ultimate defence, and research reported in Journal of Experimental Botany shows the plant may be packing extracellular vesicles with a toxic mix to do just that. Mariana Regente and colleagues (2017) worked with sunflower and pathogen Sclerotinia sclerotiorum, demonstrating how the vesicles can kill fungal cells. A separate Insight article examines the phenomenon of extracellular vesicles in plant–pathogen interactions more widely, also noting the potential for novel developments in crop protection.

Plant extracellular vesicles are incorporated by a fungal pathogen and inhibit its growth

Exchanging missives and missiles: the roles of extracellular vesicles in plant–pathogen interactions

 

Extracellular vesicles have been shown to be important in intercellular communication, and have been particularly studied in mammals. Such communication includes pathogenicity and, for example, involvement in the development of cancers – a huge area of research. So what about plants? Unfortunately we know relatively little, and although the authors note their first attempt to isolate sunflower (seed) extracellular vesicles back in 2009, other groups have followed this only with olive pollen and, finally this year, Arabidopsis leaves. The present study is therefore much needed.

Extracellular vesicles and fungal cell death

Why the slow progress? The authors particularly note a preconception that extracellular membrane structures are an artefact from cell disruption. However, their careful extraction of extracellular fluid only caused minimal lysis of cellular structures. High-throughput proteomics was used to identify a large number of extracellular proteins in sunflower, and many of these are the same as in mammals (e.g. involved in basic metabolism). Subpopulations in the plant extracellular vesicles related to cell wall remodelling and defence, and these are also present in Arabidopsis. Functional assays showed that plant extracellular vesicles can be incorporated by fungal cells, and lead to cell death. The authors are careful not to infer that the vesicles are definitely involved in plant defence, but that prize is now tantalizing.

Has the role of extracellular vesicles been overlooked? Regente et al. are clear: ‘We expect this list [of species and developmental stages from which extracellular vesicles have been isolated] to grow in the coming years, demonstrating the wide phylogenetic distribution of extracellular vesicles and their delivery and/or dissemination in the whole plant and in different growth and developmental stages ... extracellular vesicles constitute a unique package of information that can provide the simultaneous delivery of multiple messengers and components even to distant sites. Only the protein content of extracellular vesicles has been analyzed here, but according to the accumulated knowledge in other organisms, lipids and RNA might also be delivered to fungal cells, thus contributing to plant protection mechanisms against invading fungi.’

The Insight article by Petra Boevink only adds to the sense that we are at the start of something much larger: ‘The analysis of extracellular vesicles involved in plant–pathogen interactions is only just beginning but their potential for increasing our understanding of the exchanges determining disease outcomes and the potential for the development of new strategies to combat disease in economically important crops will ensure the rapid expansion of this field.’

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Journal of Experimental Botany publishes an exciting mix of research, review and comment on fundamental questions of broad interest in plant science. Regular special issues highlight key areas.

 

 



Author: Jonathan Ingram
Category: Journal of Experimental Botany
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Jonathan Ingram

Jonathan Ingram is Senior Commissioning Editor/ Science Writer for Journal of Experimental Botany. Jonathan moved from lab research into publishing and communications with the launch of Trends in Plant Science in 1995, then going on to New Phytologist and, in the third sector, Age UK and Mind.