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

Abstract

Isoprenoids are among the most abundant biogenic volatile compounds (VOCs) emitted by plants, and mediate both biotic and abiotic stress responses. Here, we provide for the first time a comparative analysis of transgenic Arabidopsis lines constitutively emitting isoprene and ocimene. Transgenic lines and Columbia-0 (Col-0) Arabidopsis were characterized under optimal, water stress, and heat stress conditions. Under optimal conditions, the projected leaf area (PLA), relative growth rate, and final dry weight were generally higher in transgenics than Col-0. These traits were associated to a larger photosynthetic capacity and CO 2 assimilation rate at saturating light. Isoprene and ocimene emitters displayed a moderately higher stress tolerance than Col-0, showing higher PLA and gas-exchange traits throughout the experiments. Contrasting behaviors were recorded for the two overexpressors under water stress, with isoprene emitters showing earlier stomatal closure (conservative behavior) than ocimene emitters (non-conservative behavior), which might suggest different induced strategies for water conservation and stress adaptation. Our work indicates that (i) isoprene and ocimene emitters resulted in enhanced PLA and biomass under optimal and control conditions and that (ii) a moderate stress tolerance is induced when isoprene and ocimene are constitutively emitted in Arabidopsis, thus providing evidence of their role as a potential preferable trait for crop improvement.

Leaf Monoterpene Emission Limits Photosynthetic Downregulation under Heat Stress in Field-Grown Grapevine

“…Monoterpene emission has been previously shown to induce heat stress tolerance in several species [ 16 , 23 , 36 ]. For instance, Quercus ilex leaves fumigated with monoterpenes had a lower decline in photosynthesis compared to non-fumigated leaves when exposed to high temperatures [ 23 ].…”

“…In particular, terpenes are the main VOCs produced by plants under HS, and high temperature has been shown to be the major driver of terpene biosynthesis [ 13 , 14 ]. The photoprotection role of terpenes has been extensively reported, and a tight link between HS tolerance and terpene emission has been often observed [ 15 , 16 ]. However, most available literature focuses on the role of isoprene, i.e., the most emitted plant hydrocarbon into the atmosphere [ 17 ].…”

“…Grapevine is not an isoprene-emitting species, although some varieties are known to produce high levels of volatile monoterpenes [ 18 ]. While numerous studies have indicated that monoterpenes may play an important regulatory role under plant stress [ 13 , 14 , 15 , 16 ], their biological functions in grapevine are still poorly understood [ 19 ]. Indeed, the emission capacity of monoterpenes from vine leaves in aromatic varieties and their potential role on heat stress tolerance has never been extensively explored.…”

Overexpression of Isoprene Synthase Affects ABA- and Drought-Related Gene Expression and Enhances Tolerance to Abiotic Stress

“…Arabidopsis Col-0 wild-type and two AdoIspS transgenic homozygous lines (AdoIspS-44 and AdoIspS-79) overexpressing the isoprene synthase gene from Arundo donax (GenBank accession No. KX906604) were used [45,79] and further characterized here. The promoter used for overexpression was the strong CaMV 35S promoter.…”

“…A few days after germination, the seedlings were transferred to pots filled with commercial soil and grown in the same condition as mentioned above. The protocol used for plants growing in hydroponics was the one described by Tocquin and colleagues [80] and the plants were maintained in a growth chamber under the environmental conditions mentioned above [79].…”