Isoprene Responses and Functions in Plants Challenged by Environmental Pressures Associated to Climate Change

Abstract

The functional reasons for isoprene emission are still a matter of hot debate. It was hypothesized that isoprene biosynthesis evolved as an ancestral mechanism in plants adapted to high water availability, to cope with transient and recurrent oxidative stresses during their water-to-land transition. There is a tight association between isoprene emission and species hygrophily, suggesting that isoprene emission may be a favorable trait to cope with occasional exposure to stresses in mesic environments. The suite of morpho-anatomical traits does not allow a conservative water use in hygrophilic mesophytes challenged by the environmental pressures imposed or exacerbated by drought and heat stress. There is evidence that in stressed plants the biosynthesis of isoprene is uncoupled from photosynthesis. Because the biosynthesis of isoprene is costly, the great investment of carbon and energy into isoprene must have relevant functional reasons. Isoprene is effective in preserving the integrity of thylakoid membranes, not only through direct interaction with their lipid acyl chains, but also by up-regulating proteins associated with photosynthetic complexes and enhancing the biosynthesis of relevant membrane components, such as mono- and di-galactosyl-diacyl glycerols and unsaturated fatty acids. Isoprene may additionally protect photosynthetic membranes by scavenging reactive oxygen species. Here we explore the mode of actions and the potential significance of isoprene in the response of hygrophilic plants when challenged by severe stress conditions associated to rapid climate change in temperate climates, with special emphasis to the concomitant effect of drought and heat. We suggest that isoprene emission may be not a good estimate for its biosynthesis and concentration in severely droughted leaves, being the internal concentration of isoprene the important trait for stress protection.

Range size and growth temperature influence Eucalyptus species responses to an experimental heatwave

“…Across species, we also observed that HSP production and isoprene emissions during the heatwave were inversely related (Figure ). Our interpretation is that maintenance of lower T leaf and higher isoprene emissions during heatwave conditions results in less damage and stress, a reduced requirement for protection from HSPs, and weaker acclimation of T max (Fini et al, ; Siwko et al, ). Together, these data provide a integrative framework linking biochemical, physiological, and whole‐tree responses to species capacity to tolerate heatwave conditions.…”

Biodiversity matters in feedbacks between climate change and air quality: a study using an individual‐based model

“…For example, the recent synthesis study by Fini et al. () found that some isoprene emitters do not respond to mild and moderate drought‐induced depressions of stomatal conductance, whole some decrease, and others increase, their emissions. There is a clear need for added research on VPD and drought impacts on VOC emissions with an emphasis on understanding the basic mechanisms that may explain such heterogeneity among species.…”

“…Many studies of water stress impacts have been conducted on different species, and the responses of isoprene emissions to such stress have not been consistent across studies, suggesting that the underlying mechanisms are not well understood. For example, the recent synthesis study by Fini et al (2017) found that some isoprene emitters do not respond to mild and moderate drought-induced depressions of stomatal conductance, whole some decrease, and others increase, their emissions. There is a clear need for added research on VPD and drought impacts on VOC emissions with an emphasis on understanding the basic mechanisms that may explain such heterogeneity among species.…”

Shoot Characterization of Isoprene and Ocimene-Emitting Transgenic Arabidopsis Plants under Contrasting Environmental Conditions

“…For instance, alien species of Hawaii emit more monoterpenes than native ones, and this has been suggested to be an indication of greater evolutionary success of alien species since monoterpene emission is associated with higher stress resistance [22]. More specifically, it was shown that isoprene biosynthesis evolved as an ancestral mechanism in plants to cope with transient oxidative stresses during their water-to-land transition [23]. Indeed, fast-growing hygrophilous Quercus species, such as most North American and some European oaks (e.g., Quercus robur), emit isoprene, whereas isoprene is replaced by monoterpenes in xeric oaks, such as Q. ilex [23,24].…”

“…More specifically, it was shown that isoprene biosynthesis evolved as an ancestral mechanism in plants to cope with transient oxidative stresses during their water-to-land transition [23]. Indeed, fast-growing hygrophilous Quercus species, such as most North American and some European oaks (e.g., Quercus robur), emit isoprene, whereas isoprene is replaced by monoterpenes in xeric oaks, such as Q. ilex [23,24]. In particular, it has been shown that ocimene is a commonly emitted monoterpene under stress conditions, in particular under heat stress [24].…”