Irene Rosa-Diaz, James Rowe, Ana Cayuela-Lopez, Vicent Arbona, Isabel Díaz, and Alexander M. Jones

Plant Physiology, 2024, 00, 1–15

https://doi.org/10.1093/plphys/kiae215

Advance access publication 26 April 2024https://doi.org/10.1093/plphys/kiae215

Abstract

Arthropod herbivory poses a serious threat to crop yield, prompting plants to employ intricate defense mechanisms against pest feeding. The generalist pest 2-spotted spider mite (Tetranychus urticae) inflicts rapid damage and remains challenging due to its broad target range. In this study, we explored the Arabidopsis (Arabidopsis thaliana) response to T. urticae infestation, revealing the induction of abscisic acid (ABA), a hormone typically associated with abiotic stress adaptation, and stomatal closure during water stress. Leveraging a Forster resonance energy transfer (FRET)-based ABA biosensor (nlsABACUS2-400n), we observed elevated ABA levels in various leaf cell types postmite feeding. While ABA's role in pest resistance or susceptibility has been debated, an ABA-deficient mutant exhibited increased mite infestation alongside intact canonical biotic stress signaling, indicating an independent function of ABA in mite defense. We established that ABA-triggered stomatal closure effectively hinders mite feeding and minimizes leaf cell damage through genetic and pharmacological interventions targeting ABA levels, ABA signaling, stomatal aperture, and density. This study underscores the critical interplay between biotic and abiotic stresses in plants, highlighting how the vulnerability to mite infestation arising from open stomata, crucial for transpiration and photosynthesis, reinforces the intricate relationship between these stress types.

Fig. 7: Stomatal density in epf1epf2, an EPF2 overexpressing line (EPF2OE), and Col-0 plants and determination of damage, stomata aperture, and temperature in the 3 genotypes after mite infestation. A) Stomatal density of Col-0, epf1epf2, and EPF2OE expressed per square millimeter from detached leaves. Numbers indicate significant differences compared to Col-0 genotype. Data are means of 5 biological replicates. One-way ANOVAfollowed by Tukey’s multiple comparisons test, P < 0.05. Detailed ANOVA results are available in Supplementary Table S5. B) Stomatal aperture represented as width/length ratio in detached leaves of Col-0, epf1epf2, and EPF2OE under mite infestation or control. Data are means of 6 biological replicates. One-way ANOVA followed by Tukey’s multiple comparisons test, P < 0.05. Detailed ANOVA results are available in Supplementary Table S5. C) Temperature in degree Celsius measured in whole plants of Col-0, epf1epf2, and EPF2OE under mite infestation or control. Significant factors (SF) indicate whether the 2 independent factors, R (mite treatment) and C (genotype), and/or their interaction I (R × C) were statistically significant (two-way ANOVA followed by Tukey’s multiple comparison test, P < 0.05). Detailed ANOVA results are available in Supplementary Table S5. Data are means of 6 biological replicates. D) Foliar damage in whole plant, expressed in square millimeters, was quantified 4 d after mite infestation of Col-0, epf1epf2, and EPF2OE. Data are means of 7 biological replicates. One-way ANOVA followed by Tukey’s multiple comparisons test, P < 0.05. Detailed ANOVA results are available in Supplementary Table S5. E) Correlation between stomatal density and damaged area for the 3 Arabidopsis genotypes (Pearson’s product moment R² = 0.992).