Abstract
As marine sessile organisms, seaweeds must respond efficiently to biotic and abiotic challenges in their natural environment to reduce the fitness consequences of wounds and oxidative stress. This study explores the early steps of the defense responses of a large marine brown alga (the tangle kelp Laminaria digitata) and investigates its ability to transmit a warning message to neighboring conspecifics. We compared the early responses to elicitation with oligoguluronates in laboratory-grown and harvested wild individuals of L. digitata. We followed the release of H2O2 and the concomitant production of volatile organic compounds. We also monitored the kinetics of expression of defense-related genes following the oxidative burst. Laboratory-grown algae were transplanted in kelp habitats to further evaluate their responses to elicitation after a transient immersion in natural seawater. In addition, a novel conditioning procedure was established to mimic field conditions in the laboratory. Our experiments showed that L. digitata integrates waterborne cues present in the kelp bed and/or released from elicited neighboring plants. Indeed, the exposure to elicited conspecifics changes the patterns of oxidative burst and volatile emissions and potentiates this kelp for faster induction of genes specifically regulated in response to oligoguluronates. Thus, waterborne signals shape the elicitor-induced responses of kelps through a yet unknown mechanism reminiscent of priming in land plants.
Highlights
In land plants, long-distance signaling mediates induced resistance against herbivores and pathogens
Three main conclusions emerge from our observations and experiments
Our results show that L. digitata sporophytes grown in the laboratory display altered GG-induced responses compared to wild conspecifics freshly harvested in the field
Summary
Long-distance signaling mediates induced resistance against herbivores and pathogens. The information is borne by systemic signals transported in the vascular system, and by volatile compounds that move in the headspace outside the plant [1] [2] Among these compounds, green-leaf volatiles and other herbivore-induced volatile organic compounds (VOCs) can mediate the systemic response to local herbivore damage in plants [1] [3] [4]. Green-leaf volatiles and other herbivore-induced volatile organic compounds (VOCs) can mediate the systemic response to local herbivore damage in plants [1] [3] [4] These VOCs diffuse in the air and potentially reach neighboring plants, allowing ‘‘plant-plant communication’’, first reported about 25 years ago in trees [5] [6]. It was proposed that this inter-plant communication is reminiscent of the potentiation of defense responses in animals [14], a so-called primed state that is associated with better or faster induction of the defense response upon biotic or abiotic stress [15]
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