Response of isoprene emission and carbon metabolism to drought in white poplar (Populus alba) saplings

Abstract

Summary• The mechanism uncoupling isoprene emission and photosynthesis under drought was investigated in Populus alba saplings.• Isoprene emission, incorporation of 13 C into the isoprene molecule, isoprene synthase (ISPS) activity, concentration and gene expression, and photosynthesis were measured as a function of the fraction of transpirable soil water (FTSW) and in plants recovering from drought.• Photosynthesis sharply declined below FTSW 30 (a FTSW of 30%) and its inhibition was not caused by metabolic factors. A decline in isoprene emission was only evident towards the FTSW endpoint. 13 C incorporation into isoprene was lower when photosynthesis was constrained by drought. ISPS activity was inhibited by mild drought, while ISPS gene expression and concentration declined in concert with isoprene emission at the FTSW endpoint. Following rewatering, isoprene emission was higher than, and photosynthesis was similar to, prestress values. ISPS activity and concentration, and 13 C incorporation into isoprene, also rapidly recovered to prestress values, while ISPS gene expression remained low in rewatered plants.• Our experiment revealed a larger contribution of alternative carbon sources to isoprene emission only when photosynthesis was dramatically constrained by drought. Isoprene emission was likely controlled at the posttranscriptional level under severe drought.

Knocking Down of Isoprene Emission Modifies the Lipid Matrix of Thylakoid Membranes and Influences the Chloroplast Ultrastructure in Poplar

“…It has been proposed that leaf isoprene emission is an important adaptation for plants, conferring tolerance to different environmental constraints (Vickers et al, 2009;Loreto and Schnitzler, 2010;Loreto and Fineschi, 2014). However, biogenic isoprene emission represents a nontrivial carbon loss in plants, particularly under stress conditions (Fang et al, 1996;Brilli et al, 2007;Teuber et al, 2008;Ghirardo et al, 2014), and the reason(s) why plants emit isoprene are still ambiguous, and the true role of isoprene emission remains elusive. Different approaches and techniques have been used to determine whether and how the cost of this expensive carbon emission is matched by the accomplishment of the physiological function in planta.…”

Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

“…Although the disconnection between photosynthesis and VTC emission has been reported, the crucial requirement of photosynthetic carbon in the biosynthesis of VTCs has also been acknowledged [35], suggesting the possibility of alternative sources of carbon for VTC synthesis. Although not fully identified and understood, in recent years labelling studies have suggested that xylem-transported carbon and chloroplast starch may be alternative sources of carbon for VTCs biosynthesis [10] [11]. It is expected that during abiotic stress related senescence where there is colossal depletion of plant starch, VTC biosynthesis will cease, however the contrary has been reported and speculating that extra-chloroplastic sources of carbon may be activated and feed carbon to stimulate VTCs biosynthesis [11].…”

Shaping the multifunctional tree: the use of Salicaceae in environmental restoration

“…The maintenance of high levels of isoprene emission, contributed by an increasingly large fraction of the carbon fixed by photosynthesis, is an indirect evidence of the importance of isoprene in protecting poplars against abiotic stresses, such as water stress (e.g., Brilli et al 2007), ozone stress (Fares et al 2006) and Ni stress (Velikova et al 2011). These findings are likely to be relevant for process-based models that account for stress effects in order to predict the emissions of isoprenoid in globally changing environmental conditions, as well as the sensitivity to high UV-A (Pallozzi et al 2012), and to scale up the impact of isoprenoid on air chemistry and quality at regional and global levels (Brilli et al 2007). Pellegrino et al (2011) have observed the important role of plant-soil interactions under different harvest intensity in sustainable bioenergy crop management, with improved soil quality in poplar plantations (short rotation forestry, SRF) in comparison with intensive cropping systems.…”