Abstract
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.
Highlights
To sustain food demands for the growing human population, it is important to increase crop yields
To grasp the overall picture, the water control was compared to a hexaethylene glycol (HEG) osmotic control at 15 mM, resembling the highest estimated molarity of the low degree of polymerization (DP) fructan solutions at 5 g L−1
Our results show that levan oligosaccharides (LOS) priming influences sugar dynamics between the in- and outside of the cell, urging further research on how LOS signals during priming affect SWEETs and other sugar transporters
Summary
To sustain food demands for the growing human population, it is important to increase crop yields. More sustainable alternatives are steadily implemented in integrated pest management systems, including biological control and immune system priming [4–6], the latter increasing the immune response of the plant to future stress exposure. Besides the recognition of non-self patterns, plants can sense and trigger defense response to self-type molecules, including molecules leaked into the apoplast during cellular rupture, or breakdown products of the plant cell wall [22,23]. Since they are under evolutionary control of the plant, these damageassociated molecular patterns (DAMPs) provide an additional advantage and are expected
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