Organ specificity of Strigolactone production in tomato plants under osmotic stress.

Strigolactones (SLs) are a new class of plant hormones influencing various aspects of development and communication with soil (micro)flora, and proposed as mediators of environmental stimuli in resource allocation processes. Data collected in Arabidopsis and Lotus japonicus suggest that SLs in shoots, but not in roots, play a positive role in adaptive adjustments to drought. In this work, we tested the hypothesis that the biosynthesis of SLs, their effects on drought resistance and cross-talk with ABA are modulated oppositely in roots and shoots of tomato plants, both under normal and stress conditions. Data will be presented supporting the concept that during osmotic stress, SL synthesis is stopped in roots (where their effect would be negative on resistance, because they repress ABA synthesis) and transferred to leaves (where they are not produced under normal conditions, but where their presence promotes ABA sensitivity). We also hypothesize that under osmotic stress, the drop of the SL levels flowing upwards from roots to shoots may act as a long-distance, circuit breaker-signal conveying the root-generated stress signal to the stem.