Use of carbon-11 inPopulusshows that exogenous jasmonic acid increases biosynthesis of isoprene from recently fixed carbon.

Ferrieri, Richard A.; Gray, Dennis W.; Babst, Benjamin A.; Schueller, Michael J.; Schlyer, David J.; Thorpe, Michael R.; Orians, Colin M.; Lerdau, Manuel

A new approach for pulse labelling of plants using the short-lived positron emitting radioisotope carbon-11 (half-life: 20.4 min) as11CO2 is reported together with its application to measuring[11C]isoprene emissions from intact leaves capturing information associated with: (1) rate of emission; (2) the relative contribution of recently fixed carbon to isoprene biosynthesis; and (3) the transit time for tracer movement through the leaf and biochemical pathways associated with isoprene biosynthesis. This approach was applied to study the response of certainPopulusspecies to exogenous treatments of jasmonic acid (JA), a plant hormone implicated in signal transduction linked to defence response against herbivory. Twelve hours after treatment of single intact leaves of aspen (Populus tremuloides) with a 1 mmJA spray, isoprene emissions from those leaves increased 1.5 times the controls from 35.4 ± 2.2 to 53.1 ± 4.8 nmol m−2 s−1.[11C]Isoprene emissions from the same leaves, reflecting the isoprene that was derived from recently fixed carbon, increased much more, to 2.2 times the controls. This increase coincided with a change in emitted[11C]isoprene from 0.31 to 0.68% of11C fixed in the leaf tissue, while the tracer transit time remained constant at 12.5 min. These results suggest that JA had no effect on enzyme kinetics involved in isoprene biosynthesis, but did impact the source of recent carbon feeding that pathway. Studies with poplar (Populus nigraclone NC 5271) showed similar trends in systemic emissions (from an untreated leaf on the same plant).

POPLARS; SALICACEAE; PLANT physiology; ISOPRENE; POSITRON emission; BIOSYNTHESIS

Plant, Cell & Environment, 2005, Vol 28, Issue 5, p591

0140-7791

Academic Journal

10.1111/j.1365-3040.2004.01303.x