5.2. Light and insect herbivory
As insects feed, they damage the plants. Insect herbivores can be
detected by the perception of damage-associated molecular patterns
(DAMPs) or of herbivore-associated molecular patterns (HAMPs) which
include fatty acid-amino conjugates (FACs; Heil, 2009). FACs are present
in the oral secretion of most lepidopteran larvae (Yoshinaga et al.,
2010). Although most of the molecular mechanisms connecting light with
herbivore attack are not yet known, observations have been made
indicating that especially UV-B light has a positive effect on the plant
responses to insect herbivores (Escobar-Bravo, Klinkhamer, & Leiss,
2017). For example, Caputo, Rutitzky and Ballare (2006) showed that UV-B
influences the attractiveness of Arabidopsis plants to
diamondback moths (Plutella xylstella ). Moreover, they described
that this beneficial effect of UV-B light on the reduction of egg number
was compromised in the jar1 mutant suggesting that intact JA
biosynthetic and signaling pathway are required for the defense
response. A similar beneficial effect of UV was also observed in thedefenseless1 tomato mutant which is deficient in JA. Here, a
strong activation of SA-associated defense responses by UV after thrips
infestation was observed (Escobar-Bravo et al., 2019). UV-B treatment
also enhanced the resistance of Arabidopsis to Spodopera
litura herbivores through a JA-dependent mechanism (Qi et al., 2018).
In addition Radhika et al. (2010) demonstrated that in lima bean
(Phaseolus lunatus ) the JA-regulated secretion of extrafloral
nectar (EFN) attracting ants which protect plants against herbivores is
dependent on light (Kazan and Manners, 2011). These examples indicate
that a close connection between herbivore resistance and UV-B signaling
acting through JA biosynthesis and signaling pathways exists.