Low levels of strigolactones in roots as a component of the systemic signal of drought stress in tomato

Abstract

SummaryStrigolactones (SL) contribute to drought acclimatization in shoots, because SL-depleted plants are hypersensitive to drought due to stomatal hyposensitivity to abscisic acid (ABA). However, under drought, SL biosynthesis is repressed in roots, suggesting organ specificity in their metabolism and role. Because SL can be transported acropetally, such a drop may also affect shoots, as a systemic indication of stress.We investigated this hypothesis by analysing molecularly and physiologically wild-type (WT) tomato (Solanum lycopersicum) scions grafted onto SL-depleted rootstocks, compared with self-grafted WT and SL-depleted genotypes, during a drought time-course.Shoots receiving few SL from the roots behaved as if under mild stress even if irrigated. Their stomata were hypersensitive to ABA (likely via a localized enhancement of SL synthesis in shoots). Exogenous SL also enhanced stomata sensitivity to ABA.As the partial shift of SL synthesis from roots to shoots mimics what happens under drought, a reduction of root-produced SL might represent a systemic signal unlinked from shootward ABA translocation, and sufficient to prime the plant for better stress avoidance.

Applying ‘drought’ to potted plants by maintaining suboptimal soil moisture improves plant water relations

“…Several candidates have been identified including changes in xylem pH and other hormones or ions (Davies et al , 2002; Ernst et al , 2010). Recent reports also suggest that drought-induced suppression of strigolactone synthesis increases stomatal sensitivity to ABA (Visentin et al , 2016). The nature of this chemical long-distance signal has attracted debate, and different mechanisms of its effect in the plant and the interaction with hydraulic signal have been proposed (Tardieu, 2016).…”

Plant Desiccation Tolerance and its Regulation in the Foliage of Resurrection “Flowering-Plant” Species

“…Whilst there have been no comprehensive studies on the involvement of strigolactones (SL) in induction of desiccation tolerance, recent reports indicate SL play important roles in responses to drought [80][81][82][83][84]. Analyses of impaired SL biosynthesis and signalling mutants in Arabidopsis suggest that SL has a role in the positive regulation of dehydration stress via both ABA-dependent and ABA-independent mechanisms [80].…”

“…The direct role of the SL compound in drought resistance of Arabidopsis as reported by Ha et al [80] was confirmed in L. japonicus by Lui et al [82] who found that SL was down-regulated in roots early during osmotic stress and that the SL decrease may be required to allow ABA production. Visentin et al [83] suggested that a reduction in SL production and its acropetal transport from tomato roots may trigger a stress response in the shoots that does not rely on ABA transport from the roots, but may lead to increased localized SL production in the shoot which could induce stomatal closure and suppress shoot branching.…”

Improving crop performance under drought – cross-fertilization of disciplines

“…Likewise, up- or down-regulation of different miRNAs was found to be associated with improved performance in rice (Chung et al , 2016) and barley (Hackenberg et al , 2015) subjected to water deficit. Hormones also play an important role in the regulation of drought acclimation/adaptation (Li et al , 2016Tardieu, 2016; Visentin et al , 2016). For instance, recent studies suggest a role for cytokinins in barley (Pospíšilová et al , 2016), Arabidopsis (Nguyen et al , 2016), tomato (Farber et al , 2016) and rice (Talla et al , 2016), and for strigolactones in tomato (Visentin et al , 2016).…”