LEAF-OF-LIFE shows that introducing isoprene emission capacity in Arabidopsis accelerated plant growth, quickened reproductive senescence, and shortened the leaf and plant lifespan. Similarly, suppressing isoprene emission in poplar (a natural isoprene-emitter) enhanced their leaf lifespan and reduced their overall growth rate. Isoprene, as shown by several experimental studies, may impart photosynthetic stability via membrane interactions and antioxidant activity under transient stressful conditions. However, our results add credence to a novel primary role for foliar isoprene emission in altering leaf and organismal development and lifespan, via isoprene emission-induced alteration in cytokinin metabolism.
(a) LEAF-OF-LIFE is the first attempt to understand the relationship between photosynthesis, isoprenoid metabolism and the rate of leaf senescence. The current view sees volatiles as both means and ends of abiotic stress response, and LEAF-OF-LIFE provides a major reappraisal of volatile hydrocarbons as regulators of plant development, a progress beyond the state-of-the art.
(b) LEAF-OF-LIFE successfully combines annual and perennial plant model systems to investigate the constraints on leaf and plant senescence. State-of-the art in plant senescence research is dominated by functional characterisation of select genes, transcriptional factors and enzymes. LEAF-OF-LIFE combines leaf age-specific genomic analysis, photosynthesis and metabolite characterisation to show how the process (senescence) impacts isoprenoid metabolism and in turn how presence of some isoprenoids shape phenotype to determine the course of senescence. This will be seen as a significant break-away from conventional template to understand senescence.
These fundamental advances in our knowledge of isoprene-cytokinin relationships in leaf development and senescence have significant implications for volatile hydrocarbon and hormone interactions overall in altering plant development, phenotype, reproductive senescence and productivity. The sequencing results (in preparation) and analyses will provide further insights into the genomic regions and transcription factors responsible for isoprene-CK mediated changes in leaf and organismal life history. We have reached an evolutionary dead-end in our quest to enhance food grain productivity both due to spatial (plant body architecture and land availability) and temporal (minimum ~70 to 90-day life cycle) limitations. New insights into volatile and hormone interactions regulating leaf senescence obtained during LEAF-OF-LIFE have informed experiments involving crop plants (commenced at CNR), where novel sustainable avenues to maintain productivity are being addressed using volatile and hormone interactions. Results of LEAF-OF-LIFE prompted the MSCA candidate and his host to take a lead role in several new proposals and projects, which take the legacy of LEAF-OF-LIFE forward.
