Response of isoprene emission and carbon metabolism to drought in white poplar (Populus alba) saplings.
The mechanism uncoupling isoprene emission and photosynthesis under drought was investigated in Populus alba saplings. Isoprene emission, incorporation of 13C 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 FTSW30 (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. 13C 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 13C 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.
Brilli
Federico
F
CNR - Istituto di Biologia Agroambientale e Forestale, Via Salaria km 29.300, 00016 Monterotondo Scalo (Roma), Italy.
Barta
Csengele
C
CNR - Istituto di Biologia Agroambientale e Forestale, Via Salaria km 29.300, 00016 Monterotondo Scalo (Roma), Italy.
Fortunati
Alessio
A
CNR - Istituto di Biologia Agroambientale e Forestale, Via Salaria km 29.300, 00016 Monterotondo Scalo (Roma), Italy.
Lerdau
Manuel
M
Department of Environmental Sciences, University of Virginia, Clark Hall, 291 McCormick Road, PO Box 400123, Charlottesville, VA 22904-4123, USA.
Loreto
Francesco
F
CNR - Istituto di Biologia Agroambientale e Forestale, Via Salaria km 29.300, 00016 Monterotondo Scalo (Roma), Italy.
Centritto
Mauro
M
CNR - Istituto sull'Inquinamento Atmosferico, Via Salaria km 29.300, 00016 Monterotondo Stazione, Rome, Italy.
D002070:Butadienes / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D045782:Hemiterpenes / Q000378:metabolism*; D010420:Pentanes / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism; D032107:Populus / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D014867:Water; C005059:isoprene; D002244:Carbon