The same boat, different storm: stress volatile emissions in response to biotrophic fungal infections in primary and alternate hosts

ABSTRACT

Rust infection results in stress volatile emissions, but due to the complexity of host-pathogen interaction and variations in innate defense and capacity to induce defense, biochemical responses can vary among host species. Fungal-dependent modifications in volatile emissions have been well documented in numerous host species, but how emission responses vary among host species is poorly understood. Our recent experiments demonstrated that the obligate biotrophic crown rust fungus (P. coronata) differently activated primary and secondary metabolic pathways in its primary host Avena sativa and alternate host Rhamnus frangula. In A. sativa, emissions of methyl jasmonate, short-chained lipoxygenase products, long-chained saturated fatty acid derivatives, mono- and sesquiterpenes, carotenoid breakdown products, and benzenoids were initially elicited in an infection severity-dependent manner, but the emissions decreased under severe infection and photosynthesis was almost completely inhibited. In R. frangula, infection resulted in low-level induction of stress volatile emissions, but surprisingly, in enhanced constitutive isoprene emissions, and even severely-infected leaves maintained a certain photosynthesis rate. Thus, the same pathogen elicited a much stronger response in the primary than in the alternate host. We argue that future work should focus on resolving mechanisms of different fungal tolerance and resilience among primary and secondary hosts.

KEYWORDS:

• defense signaling pathways
• host-pathogen interaction
• isoprene
• infection severity
• limiting nutrient
• pathogen stress
• photosynthesis
• volatile organic compounds

Acknowledgments

This research was funded by the European Commission through the European Research Council (advanced grant 322603, SIP-VOL+), the EU Regional Development Fund within the framework of the Centre of Excellence EcolChange (2014-2020.4.01.15-0002), and the Estonian University of Life Sciences (base funding P190259PKTT). The equipment used in the study was partly purchased from funding by the EU Regional Development Fund (AnaEE Estonia, 2014-2020.4.01.20-0285, and the project “Plant Biology Infrastructure-TAIM”, 2014-2020.4.01.20-0282) and Estonian Research Council (“Plant Biology Infrastructure – TAIM”, TT5).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by theby the European Commission through the European Research Council (advanced grant 322603, SIP-VOL+), the EU Regional Development Fund within the framework of the Centre of Excellence EcolChange (2014-2020.4.01.15-0002), and the Estonian University of Life Sciences (base funding P190259PKTT). The equipment used in the study was partly purchased from funding by the EU Regional Development Fund (AnaEE Estonia, 2014-2020.4.01.20-0285, and the project “Plant Biology Infrastructure-TAIM”, 2014-2020.4.01.20-0282) and Estonian Research Council (“Plant Biology Infrastructure – TAIM”, TT5).