Differential Accumulation of Dimethylallyl Diphosphate in Leaves and Needles of Isoprene- and Methylbutenol-Emitting and Nonemitting Species

Abstract

The biosynthesis and emission of volatile plant terpenoids, such as isoprene and methylbutenol (MBO), depend on the chloroplastic production of dimethylallyl diphosphate (DMAPP). To date, it has been difficult to study the relationship of cellular DMAPP levels to emission of these volatiles because of the lack of a sensitive assay for DMAPP in plant tissues. Using a recent DMAPP assay developed in our laboratories, we report that species with the highest potential for isoprene and MBO production also exhibit elevated light-dependent DMAPP production, ranging from 110% to 1,063%. Even species that do not produce significant amounts of volatile terpenoids, however, exhibit some potential for light-dependent production of DMAPP. We used a nonaqueous fractionation technique to determine the intracellular distribution of DMAPP in isoprene-emitting cottonwood (Populus deltoides) leaves; approximately 65% to 70% of the DMAPP recovered at midday occurred in the chloroplasts, indicating that most of the light-dependent production of DMAPP was chloroplastic in origin. The midday concentration of chloroplastic DMAPP in cottonwood leaves is estimated to be 0.13 to 3.0 mm, which is consistent with the relatively high K m s that have been reported for isoprene synthases (0.5-8 mm). The results provide support for the hypothesis that the light dependence of isoprene and MBO emissions is in part due to controls over DMAPP production.A wide array of volatile organic compounds (VOCs) are emitted into the atmosphere by the leaves of many plant species (Graedel, 1979; Lerdau et al., 1997; Kesselmeier and Staudt, 1999; Kreuzwieser et al., 1999). Among the biogenic VOCs studied to date, isoprene (2-methyl-1,3-butadiene) is quantitatively the most important, with as much as 500 Tg year Ϫ1 estimated to be emitted globally from vegetation (Guenther et al., 1995), exerting profound effects on atmospheric chemistry (Monson and Holland, 2001). In the presence of nitrogen oxides and sunlight, isoprene oxidation can lead to the production of tropospheric ozone (Trainer et al., 1987; Chameides et al., 1988). Not all plants emit isoprene. Most that do are woody in growth habit and are represented by North American species of oaks (Quercus spp.), willows (Salix spp.), poplars (Populus spp.), and spruce (Abies spp.; Harley et al., 1999).Methylbutenol (MBO; 2-methyl-3-buten-2-ol) is a C 5 terpenoid, similar to isoprene, that is emitted by several pine species native to the western United States, including ponderosa (Pinus ponderosa), lodgepole (Pinus contorta), and gray pine (Pinus sabiniana; Harley et al., 1998). Emissions of MBO from pine needles are dependent on both photosynthetic photon flux density (PPFD) and temperature (Harley et al., 1998), showing behavior that is similar to leaf emissions of isoprene (Monson and Fall, 1989;Loreto and Sharkey, 1990). Like isoprene, MBO emissions from forests represent a significant source of reactive carbon to the atmosphere (Harley et al., 1998). Despite the important influence of isoprene and MBO ...

Strong correlation between isoprene emission and gross photosynthetic capacity during leaf phenology of the tropical tree species Hymenaea courbaril with fundamental changes in volatile organic compounds emission composition during early leaf development

“…Correspondingly the k cat , being a direct measure of the catalytic efficiency, was found to be relatively low for isoprene synthase, similar to those of other allylic diphosphate-utilizing enzymes (Table 2). In mature oak leaves (Quercus robur) the calculated chloroplastidic DMAPP concentrations were found to be close to the apparent K m value of oak isoprene synthase (Lehning et al 1999;Rosenstiel et al 2002), supporting the hypothesis that the availability of DMAPP can be one of the major driving forces of isoprene synthase activity in mature leaves. The production of the intermediates is light-induced and a positive correlation between leaf DMAPP levels (as substrate for isoprene synthase) and photosynthate flux led to the hypothesis that the lightdependence of isoprene emission is in part due to controls over DMAPP production and content (Brüggemann & Schnitzler 2002a, b;Rosenstiel et al 2002).…”

“…On the other hand the demand for DMAPP is very high during leaf expansion by simultaneous investment in growth and greening, as DMAPP is one of the essential precursors of all plant terpenoids (about 30 000 have been identified in leaves), among them those needed for the assembly of the photosynthetic apparatus. Indeed Rosenstiel et al (2002) found that young leaves of cotton wood contained significantly lower levels of DMAPP than mature leaves. Due to the high K m value of isoprene synthase, poor substrate availability due to partitioning to competing pathways may prevent isoprene synthase to be active.…”

“…For monoterpenes similar physiological functions as for isoprene were postulated, namely the protection of the photosynthetic apparatus against high temperatures episodes (Sharkey & Singsaas 1995;Loreto et al 1998;Delfine et al 2000) and against oxidative damage (O 3 , OH, H 2 O 2 , HO 2 ) Loreto & Velikova 2001). In extension to the hypothesis of Rosenstiel et al (2002), stating that the availability of DMAPP may explain part of the ontogenetic delay of isoprene emission versus photosynthesis (which could not be shown for H. courbaril), low DMAPP availability may also confer a reasonable explanation for the observed change between monoterpene and isoprene biosynthesis/emission in H. courbaril. For monoterpene biosynthesis DMAPP must be converted to geranylpyrophosphate (GPP) by the enzyme GPP synthase (GPPS).…”

“…Previous studies have emphasized the essential function of isoprene synthase enzyme activation in regulating isoprene biosynthesis and emission Lehning et al 1999;Lichtenthaler 1999;Lehning et al 2001). More recent investigations focused on the regulatory role of the availability of its substrate DMAPP (Brüggemann & Schnitzler 2002a, b;Rosenstiel et al 2002), or other intermediates and enzymes of this biosynthetic pathway (Brüggemann & Schnitzler 2002c;Wolfertz et al 2003). Isoprene synthase seems to have relatively poor catalytic efficiency, usually expressed in terms of the Michaels constant (K m ), which is the substrate DMAPP concentration that produces onehalf maximal reaction rate, and the turnover number (k cat ), which is the number of substrate molecules that each enzyme processes per unit time under optimum conditions (substrate saturated).…”

Metabolomic analysis ofArabidopsisreveals hemiterpenoid glycosides as products of a nitrate ion-regulated, carbon flux overflow

“…In Populus sp. a link between low NO 3 − and isoprene has been established (7) and other work indicates that DMAPP levels may govern the rate of emission (31,32).…”