Sweet Immunity Aspects during Levan Oligosaccharide-Mediated Priming in Rocket against Botrytis cinerea

New strategies are required for crop protection against biotic stress. Naturally derived molecules, including carbohydrates such as fructans, can be used in priming or defense stimulation. Rocket (Eruca sativa) is an important leafy vegetable and a good source of antioxidants. Here, we tested the efficacy of fructan-induced immunity in the Botrytis cinerea pathosystem. Different fructan types of plant and microbial origin were considered and changes in sugar dynamics were analyzed. Immune resistance increased significantly after priming with natural and sulfated levan oligosaccharides (LOS). No clear positive effects were observed for fructo-oligosaccharides (FOS), inulin or branched-type fructans. Only sulfated LOS induced a direct ROS burst, typical for elicitors, while LOS behaved as a genuine priming compound. Total leaf sugar levels increased significantly both after LOS priming and subsequent infection. Intriguingly, apoplastic sugar levels temporarily increased after LOS priming but not after infection. We followed LOS and small soluble sugar dynamics in the apoplast as a function of time and found a temporal peak in small soluble sugar levels. Although similar dynamics were also found with inulin-type FOS, increased Glc and FOS levels may benefit B. cinerea. During LOS priming, LOS- and/or Glc-dependent signaling may induce downstream sweet immunity responses.

Automated summary

Research investigated the use of fructan-induced immunity against Botrytis cinerea in crops. Results showed that immune resistance significantly increased after priming with natural and sulfated levan oligosaccharides (LOS). Fructo-oligosaccharides (FOS), inulin, and branched-type fructans had no clear positive effects. Only sulfated LOS induced a direct ROS burst, while LOS acted as a priming compound. Total leaf sugar levels increased after LOS priming and subsequent infection, with a temporary increase in apoplastic sugar levels after LOS priming. Dynamics of LOS and small soluble sugars in the apoplast showed a temporal peak.