Emission of herbivore elicitor‐induced sesquiterpenes is regulated by stomatal aperture in maize (Zea mays) seedlings

Abstract

Maize seedlings emit sesquiterpenes during the day in response to insect herbivory. Parasitoids and predators use induced volatile blends to find their hosts or prey. To investigate the diurnal regulation of biosynthesis and emission of induced sesquiterpenes, we applied linolenoyl-L-glutamine (LG) to maize seedlings in the morning or evening using a cut-stem assay and tracked farnesene emission, in planta accumulation, as well as transcript levels of farnesyl pyrophosphate synthase 3 (ZmFPPS3) and terpene synthase10 (ZmTPS10) throughout the following day. Independent of time of day of LG treatment, maximum transcript levels of ZmFPPS3 and ZmTPS10 occurred within 3-4 h after elicitor application. The similarity between the patterns of farnesene emission and in planta accumulation in light-exposed seedlings in both time courses suggested unobstructed emission in the light. After evening induction, farnesene biosynthesis increased dramatically during early morning hours. Contrary to light-exposed seedlings dark-kept seedlings retained the majority of the synthesized farnesene. Two treatments to reduce stomatal aperture, dark exposure at midday, and abscisic acid treatment before daybreak, resulted in significantly reduced amounts of emitted and significantly increased amounts of in planta accumulating farnesene. Our results suggest that stomata not only play an important role in gas exchange for primary metabolism but also for indirect plant defences.

Herbivore-induced plant volatiles in natural and agricultural ecosystems: open questions and future prospects

“…For example, changes in temperature and precipitation patterns may lead to increased drought stress in some regions. Recent findings indicate that at least some HIPV are released through the stomata [66 ], suggesting that increased drought stress may alter patterns of plant volatile release via the induction of stomatal closure as well as via other drought stressrelated physiological effects [67,68]. Such effects could also alter diurnal patterns of HIPV emission (if stomata opening shifts to times of higher humidity, such as early morning), potentially creating a mismatch between the temporal availability of HIPV cues and periods of peak natural enemy foraging activity [69,70].…”

Rethinking how volatiles are released from plant cells

“…In vegetative organs, VOCs are often synthesized in the secretory cells of glandular trichomes located on the leaf surface [24][25][26][27] and then secreted to a sac created by an extension of the cuticle, where they are stored until mechanical disruption [28][29][30]. When trichomes are not involved in vegetative VOC production, these compounds are often synthesized in mesophyll cells [31,32], mainly in the palisade parenchyma [33], and released through stomata [34][35][36][37], mechanical disruption, or emission through cuticle [36]. Regardless of the tissue and whether they exit via stomata, at the subcellular level, VOCs must move from their site of biosynthesis through the cytosol to the plasma membrane, and then subsequently traverse the plasma membrane, hydrophilic cell wall, and, in some cases, the cuticle to exit the cell.…”

A small, differentially regulated family of farnesyl diphosphate synthases in maize (Zea mays) provides farnesyl diphosphate for the biosynthesis of herbivore-induced sesquiterpenes

“…We conducted a time course experiment with 8 time points within 10 h after leaf herbivory. Herbivory was mimicked by leaf damage and treatment with buffer or the elicitor linolenoyl-L-glutamine in an attempt to make the kinetics comparable to those of the genes fpps3 and tps10 presented by Seidl- Adams et al (2014). The induction kinetics of fpps3 and tps23 were very similar (Fig.…”