Isoprene function in two contrasting poplars under salt and sunflecks.

Area of Science:

• Plant Physiology
• Biochemistry
• Environmental Stress Biology

Background:

• Biogenic volatile organic compounds (BVOCs) play roles in plant stress responses.
• Isoprene emission is a key BVOC pathway in many plants, including poplars.
• Understanding isoprene's function under combined stresses like salinity and heat is crucial for predicting plant resilience.

Purpose of the Study:

• To investigate the impact of combined salt and sunfleck stress on isoprene emissions and photosynthetic gas exchange in salt-sensitive and salt-tolerant poplars.
• To elucidate the role of isoprene in poplar survival and thermotolerance under abiotic stress.
• To analyze metabolic changes associated with isoprene production and salt stress.

Main Methods:

• Controlled experiments exposing poplars to high salinity, high temperature, and sunflecks.
• (13)CO2 labeling to trace isoprene precursor allocation.
• Photosynthetic gas exchange measurements.
• Lipid composition analysis and metabolomics profiling.
• Long-term temperature stress experiments.

Main Results:

• Combined salt and sunfleck treatment increased isoprene emission capacity in both poplar species, but reduced photosynthesis in the salt-sensitive species.
• Isoprene itself did not confer significant salt tolerance; non-isoprene-emitting poplars showed only slightly reduced photosynthetic performance under salt stress.
• Isoprene plays a vital role in thermotolerance, with non-isoprene-emitting leaves collapsing under high temperatures.
• Metabolomics revealed distinct patterns in flavonoids, sterols, and carbon fixation metabolites related to isoprene presence and salt stress.

Conclusions:

• Isoprene's primary role in poplars under tested conditions is thermotolerance, not direct salt stress mitigation.
• Engineered poplars with reduced isoprene emission may lack resilience to high-temperature episodes.
• Differential precursor allocation and alternative carbon source utilization influence isoprene biosynthesis under stress.