09 Salt and Wine - Jasmonic Acid Helps
Ismail A, Riemann M, Nick P (2012) The jasmonate pathway mediates salt tolerance in grapevines. J Exp Bot 63, 2127-2139 (65 quotations, state 04.07.2019) - pdf
What is it about? Grapes, with their deep roots, are actually well adapted to drought. However, in consequence of climate change, even viticulture progressively needs to rely on artificial irrigation. The evaporating water (mostly not of good quality) leaves salt behind. In the Mediterranean, but also in Australia, South Africa, Chile, and California, salt stress develops into a major challenge for viticulture. Can we protect grapes against salt stress? This first requires to understand, how they perceive salinity, and respond to it.
What came out? We looked into Nature's trick box, comparing two wild grapes from North America that differ in salt tolerance. To dissect this on the cellular level, we did not work with entire plants, but with cell cultures derived from the Rock Grape (Vitis rupestris), salt tolerant species, and the River Grape (Vitis riparia), a susceptible species. The difference could be traced back to the cell culttures, which allowed to compare. We investigated, which genes are activated in response to salt stress, and how the two cell lines differed in this response. Eventually, we could pinpoint the gene JAZ1 as key for salt tolerance. This factor is activated by the "plant adrenalin" jasmonic acid and regulates stress responses - what involves its own formation leading to a negative feedback of jasmonate signalling. This negative feedback leads to a short, but immediately silenced response of signalling, basically a "stress pulse", but not a "continuous stress". This "stress pulse" is very efficient to evoke, in the Rock Grape, adaptation to salt. For instance, salt pumps are activated that sequester the salt into the vacuole, such that they cannot do damage to the cell. In the River Grape, instead a slow, but continuous increase of jasmonate signalling induces cell death. The parallelity to human stress reactions is evident - stress reactions that are rapidly quelled are not causing harm and even can be beneficial, while continuous stress makes people turn ill.