Plant defense under Arctic light conditions: Can plants withstand invading pests?

24.11.2022

Insect populations are moving polewards at a rate of 2.7 km year-1

Can Arctic plants withstand the expected fast pest invasion caused by rising temperatures?

-> Let's think about it with us from the view of plant defence physiology!

-> Take a look at our freshly published theoretical paper on plant defences affected by latitude, light and current knowledge on phytochrome signalling:

Global warming is predicted to change the growth conditions for plants and crops in regions at high latitudes (>60° N), including the Arctic. This will be accompanied by alterations in the composition of natural plant and pest communities, as herbivorous arthropods will invade these regions as well. Interactions between previously non-overlapping species may occur and cause new challenges to herbivore attacks. However, plants growing at high latitudes experience less herbivory compared to plants growing at lower latitudes. We hypothesize that this finding is due to a gradient of constitutive chemical defense towards the Northern regions. We further hypothesize that a higher level of defensive compounds is mediated by the higher level of the defense-related phytohormone jasmonate. Because its biosynthesis is light-dependent, Arctic summer daylight conditions can promote jasmonate accumulation and, hence, downstream physiological responses. A pilot study with bilberry (Vaccinium myrtillus) plants grown under different light regimes supports the hypothesis.


Check out the full text

Mithöfer, A., Riemann, M., Faehn, C. A., Mrazova, A., & Jaakola, L. (2022). Plant defense under Arctic light conditions: Can plants withstand invading pests?. Frontiers in Plant Science, 13.

Figure 1. Hypothetic distribution of plant chemical defenses along latitudinal gradients. (A) Variability of chemical defenses along latitudinal and their corresponding day length gradients. (B) Proposed decrease of palatability for herbivorous insects feeding on leaves with increasing latitude. © Map of Europe in (A) European Environment Agency (EEA).

Figure 2. Jasmonate biosynthesis. Simplified scheme showing the generation of jasmonoyl-isoleucine (JA-Ile) via two alternative jasmonic acid (JA) pathways. Enzymatic reactions and corresponding enzymes are indicated in red. Transport between cell compartments is depicted by black dotted arrows. Abbreviations: LOX, Lipoxygenase; AOS, Allene Oxide Synthase; AOC, Allene Oxide Cyclase; OPDA, 12-oxo-phytodienoic acid; dnOPDA, dinor-OPDA; tnOPDA, tetranor-OPDA; 4,5-ddh-JA, 4,5-didehydro-JA; OPR, OPDA Reductase; OPC-8, 8-(3-oxo-2-(pent-2-enyl)cyclopentenyl)octanoic acid; JA, jasmonic acid; JAR, Jasmonate resistant; JA-Ile, jasmonoyl-isoleucine. Scheme modified after Chini et al. (2018) and Wasternack and Song (2017).

Figure 3. Illustration of interactions among sunlight, jasmonates, photomorphogenesis, and defense. Arrows imply activation, T-bars indicate inhibition of an interaction/process. JAs, jasmonates; JAR1/FIN219, Jasmonate resistant1/Far-red insensitive 219; COP1, Constitutive photo-morphogenic1, acts only in the dark on photomorphogenesis; Phy, Phytochrome; HY5, Elongated hypocotyl 5; MYC2/3, Transcription factors; photoreceptors include phytochrome, blue light, and UV-B receptors; sunlight represent R:FR >> 1. For details see the full paper.

Figure 4. Phytohormones in bilberry (Vaccinium myrtillus) plants grown under different light regimes. (A) Accumulation of jasmonic acid (JA) in bilberry leaves grown for 14 days under 24 h (24 L) and 12 h (12 L/12 D) light regime and collected every 6 hrs, i.e. for the 12 L/12 D light regime two times each in the light and in the dark; ***: P < 0.001 (Welch-test). Phytohormone analysis was done according to Dávila-Lara et al. (2021). (B) Principal component analysis of amounts of various defense-related phytohormones (JA, JA-Ile, SA, IAA, ABA) accumulating under 12 h light (L/D) and 24 h light (Light) in bilberry leaves. PC, principal component (% of total variance); confidence area, 95% PCA analysis.

Figure 5. Model summarizing the suggested impact of arctic summer light conditions on jasmonates (JAs) and plant defense.
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