Sucrose signaling pathways leading to fructan and anthocyanin accumulation: A dual function in abiotic and biotic stress responses?

• Sucrose-specific signaling pathway leading to anthocyanin biosynthesis.
• Sucrose-specific signaling pathway leading to fructan biosynthesis.
• The central role of SnRKs in sugar signaling pathways.
• The contribution of sucrose-specific signaling pathways under abiotic and biotic stresses.
• The emerging role of the “sweet immunity” concept in plant stress responses.

In a changing world, plants are exposed to ever changing environmental conditions. Since plants cannot escape from their environment, they require extra flexibility to adapt themselves to stressful conditions, such as drought and salt stresses. One of these adaptations includes the vacuolar accumulation of fructans (fructose-based oligo-and polysaccharides) and anthocyanins (a type of glucosylated flavonoids), both involved in biotic and abiotic stress responses. As part of the recently emerging concept of “sweet immunity” leading to improved tolerance to both abiotic and biotic stresses, possible synergisms between these two types of biomolecules are discussed. Moreover, sucrose-specific signaling pathways stimulate both the production of fructans and anthocyanins, with a central role for MYB-type of transcription factors and a strict dependence on Ca2+. This review summarizes recent insights in these signal transduction pathways and their cross-talks with hormonal signaling pathways, with focus on the stress hormone abscisic acid. Although most of the current research is dedicated on the model plant Arabidopsis thaliana, we also focus on wheat as an example of an economically important crop that is able to accumulate both fructans and anthocyanins under various stresses.