TY - JOUR

T1 - Root-associated entomopathogenic fungi modulate their host plant’s photosystem ii photochemistry and response to herbivorous insects

AU - Moustaka, Julietta

AU - Meyling, Nicolai Vitt

AU - Hauser, Thure Pavlo

N1 - Funding Information: Funding: This research was funded by the European Union’s Horizon 2020 research and Innovation programme, Microbe Induced Resistance to Agricultural Pests (MiRA), Grant agreement No 765290. Funding Information: This research was funded by the European Union?s Horizon 2020 research and Innovation programme, Microbe Induced Resistance to Agricultural Pests (MiRA), Grant agreement No 765290. The authors would like to thank Michael Moustakas (Department of Botany, Aristotle University of Thessaloniki) for providing the Chlorophyll Fluorometer used in this study. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2022

Y1 - 2022

N2 - The escalating food demand and loss to herbivores has led to increasing interest in using resistance-inducing microbes for pest control. Here, we evaluated whether root-inoculation with fungi that are otherwise known as entomopathogens improves tomato (Solanum lycopersicum) leaflets’ reaction to herbivory by Spodoptera exigua (beet armyworm) larvae using chlorophyll fluorescence imaging. Plants were inoculated with Metarhizium brunneum or Beauveria bassiana, and photosystem II reactions were evaluated before and after larval feeding. Before herbivory, the fraction of absorbed light energy used for photochemistry (ΦPSII) was lower in M. brunneum-inoculated than in control plants, but not in B. bassiana-inoculated plants. After herbivory, however, ΦPSII increased in the fungal-inoculated plants compared with that before herbivory, similar to the reaction of control plants. At the same time, the fraction of energy dissipated as heat (ΦNPQ) decreased in the inoculated plants, resulting in an increased fraction of nonregulated energy loss (ΦNO) in M. brunneum. This indicates an increased singlet oxygen (1 O2) formation not detected in B. bassiana-inoculated plants, showing that the two entomopathogenic fungi differentially modulate the leaflets’ response to herbivory. Overall, our results show that M. brunneum inoculation had a negative effect on the photosynthetic efficiency before herbivory, while B. bassiana inoculation had no significant effect. However, S. exigua leaf biting activated the same compensatory PSII response mechanism in tomato plants of both fungal-inoculated treatments as in control plants.

AB - The escalating food demand and loss to herbivores has led to increasing interest in using resistance-inducing microbes for pest control. Here, we evaluated whether root-inoculation with fungi that are otherwise known as entomopathogens improves tomato (Solanum lycopersicum) leaflets’ reaction to herbivory by Spodoptera exigua (beet armyworm) larvae using chlorophyll fluorescence imaging. Plants were inoculated with Metarhizium brunneum or Beauveria bassiana, and photosystem II reactions were evaluated before and after larval feeding. Before herbivory, the fraction of absorbed light energy used for photochemistry (ΦPSII) was lower in M. brunneum-inoculated than in control plants, but not in B. bassiana-inoculated plants. After herbivory, however, ΦPSII increased in the fungal-inoculated plants compared with that before herbivory, similar to the reaction of control plants. At the same time, the fraction of energy dissipated as heat (ΦNPQ) decreased in the inoculated plants, resulting in an increased fraction of nonregulated energy loss (ΦNO) in M. brunneum. This indicates an increased singlet oxygen (1 O2) formation not detected in B. bassiana-inoculated plants, showing that the two entomopathogenic fungi differentially modulate the leaflets’ response to herbivory. Overall, our results show that M. brunneum inoculation had a negative effect on the photosynthetic efficiency before herbivory, while B. bassiana inoculation had no significant effect. However, S. exigua leaf biting activated the same compensatory PSII response mechanism in tomato plants of both fungal-inoculated treatments as in control plants.

KW - Beauveria bassiana

KW - Chlorophyll fluorescence imaging

KW - Compensatory process

KW - Herbivory costs

KW - Metarhizium brunneum

KW - Non-photochemical quenching

KW - Photosynthetic efficiency

KW - Singlet oxygen

KW - Solanum lycopersicum

KW - Spodoptera exigua

U2 - 10.3390/molecules27010207

DO - 10.3390/molecules27010207

M3 - Journal article

C2 - 35011439

AN - SCOPUS:85122028780

VL - 27

JO - Molecules

JF - Molecules

SN - 1420-3049

IS - 1

M1 - 207

ER -