Hormetic Responses of Photosystem II in Tomato to Botrytis cinerea

Maria-Lavrentia Stamelou; Ilektra Sperdouli; Ioanna Pyrri; Ioannis-Dimosthenis S Adamakis; Michael Moustakas

doi:10.3390/plants10030521

Hormetic Responses of Photosystem II in Tomato to Botrytis cinerea

Plants (Basel). 2021 Mar 10;10(3):521. doi: 10.3390/plants10030521.

Authors

Maria-Lavrentia Stamelou^{1

2}, Ilektra Sperdouli², Ioanna Pyrri³, Ioannis-Dimosthenis S Adamakis¹, Michael Moustakas⁴

Affiliations

¹ Section of Botany, Department of Biology, National and Kapodistrian University of Athens, GR-15784 Athens, Greece.
² Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization-Demeter, Thermi, GR-57001 Thessaloniki, Greece.
³ Section of Ecology & Systematics, Department of Biology, National and Kapodistrian University of Athens, GR-15784 Athens, Greece.
⁴ Department of Botany, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.

Abstract

Botrytis cinerea, a fungal pathogen that causes gray mold, is damaging more than 200 plant species, and especially tomato. Photosystem II (PSII) responses in tomato (Solanum lycopersicum L.) leaves to Botrytis cinerea spore suspension application were evaluated by chlorophyll fluorescence imaging analysis. Hydrogen peroxide (H₂O₂) that was detected 30 min after Botrytis application with an increasing trend up to 240 min, is possibly convening tolerance against B. cinerea at short-time exposure, but when increasing at relative longer exposure, is becoming a damaging molecule. In accordance, an enhanced photosystem II (PSII) functionality was observed 30 min after application of B. cinerea, with a higher fraction of absorbed light energy to be directed to photochemistry (Φ_PSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in a significant decrease in the dissipated non-regulated energy (Φ_NO), indicating a possible decreased singlet oxygen (¹O₂) formation, thus specifying a modified reactive oxygen species (ROS) homeostasis. Therefore, 30 min after application of Botrytis spore suspension, before any visual symptoms appeared, defense response mechanisms were triggered, with PSII photochemistry to be adjusted by NPQ in a such way that PSII functionality to be enhanced, but being fully inhibited at the application spot and the adjacent area, after longer exposure (240 min). Hence, the response of tomato PSII to B. cinerea, indicates a hormetic temporal response in terms of "stress defense response" and "toxicity", expanding the features of hormesis to biotic factors also. The enhanced PSII functionality 30 min after Botrytis application can possible be related with the need of an increased sugar production that is associated with a stronger plant defense potential through the induction of defense genes.

Keywords: biotic stress; chlorophyll fluorescence imaging; hormesis; hydrogen peroxide (H2O2); non-photochemical quenching (NPQ); photoprotection; photosynthesis; reactive oxygen species (ROS); stress defense; toxicity.