Drought and flooding have distinct effects on herbivore‐induced responses and resistance inSolanum dulcamara

Abstract

In the field, biotic and abiotic stresses frequently co-occur. As a consequence, common molecular signalling pathways governing adaptive responses to individual stresses can interact, resulting in compromised phenotypes. How plant signalling pathways interact under combined stresses is poorly understood. To assess this, we studied the consequence of drought and soil flooding on resistance of Solanum dulcamara to Spodoptera exigua and their effects on hormonal and transcriptomic profiles. The results showed that S. exigua larvae performed less well on drought-stressed plants than on well-watered and flooded plants. Both drought and insect feeding increased abscisic acid and jasmonic acid (JA) levels, whereas flooding did not induce JA accumulation. RNA sequencing analyses corroborated this pattern: drought and herbivory induced many biological processes that were repressed by flooding. When applied in combination, drought and herbivory had an additive effect on specific processes involved in secondary metabolism and defence responses, including protease inhibitor activity. In conclusion, drought and flooding have distinct effects on herbivore-induced responses and resistance. Especially, the interaction between abscisic acid and JA signalling may be important to optimize plant responses to combined drought and insect herbivory, making drought-stressed plants more resistant to insects than well-watered and flooded plants.

Plant Resistance Inducers against Pathogens in Solanaceae Species—From Molecular Mechanisms to Field Application

“…For example, it could be of interest to study how combined stresses, e.g., pathogen infection combined with abiotic stress or herbivory, would influence transgenerational IR. A recent study on the wild Solanum dulcamara showed that both water stress and herbivory increased abscisic acid (ABA) and JA levels, making drought-stressed plants more resistant to attack by Spodoptera exigua larvae [154]. …”

Mechanisms and ecological implications of plant‐mediated interactions between belowground and aboveground insect herbivores

“…For example, ABA levels were increased systemically after BG herbivory in maize plants . It is known that ABA plays a role in plant responses to both wounding and abiotic stresses including drought (Christmann et al 2006;Hauser et al 2011;Nguyen et al 2016). Since herbivory by BG or AG chewing insects is accompanied by wounding and water loss (Aldea et al 2005;Erb et al 2009a;Consales et al 2011), it seems likely that root herbivore-mediated abiotic stress may result in systemic induction of AG ABA levels, which may affect AG induced defenses .…”

Drought-stressed tomato plants trigger bottom-up effects on key mite pests

“…In S. dulcamara, a species close to tomato, drought has been shown to increase the levels of JA and ABA, increasing resistance to the beet armyworm Spodoptera exigua (Nguyen 2016a) with a similar effect observed in tomato (English-Loeb et al, 1997). Interestingly, ABA-deficient tomato plants reduced the resistance to S. exigua but increased the SA linked defense response increasing the resistance to biotrophic pathogens (Thaler and Bostock, 2004).…”

“…Both serine and cysteine PIs are induced by drought in Solanum dulcamara, rice, potato and Arabidopsis (Kang et al, 2002;Huang et al, 2007;Zhang et al, 2008;Nguyen et al, 2016a), with not clear pattern in tomato (English-Loeb et al, 1997). They have been proposed to regulate the proteases induced by drought, delaying leaf senescence and thus increasing drought tolerance (Huang et al, 2007;Zhang et al, 2008;Diaz-Mendoza et al, 2014).…”

“…In tomato, a synergistic effect between ABA and JA has been reported in the response to drought stress and herbivory (Muñoz-Espinosa et al, 2015;Nguyen et al, 2016a), the transcription factor MYC2 playing a key role in regulating the crosstalk between these two phytohormones (Kazan and Manners, 2013). In S. dulcamara, a species close to tomato, drought has been shown to increase the levels of JA and ABA, increasing resistance to the beet armyworm Spodoptera exigua (Nguyen 2016a) with a similar effect observed in tomato (English-Loeb et al, 1997).…”