Abstract
Main conclusion: The transcripts of transgenic prosystemin (PS) gene are mobile and the PS mRNA can be translated into protein in tomato and tobacco plants. Systemin (SYS) and its precursor protein, prosystemin (PS), are upstream components of the wound-induced signaling pathway in tomato. Although the mobile signal(s) for wound responses has been the subject of considerable research, its identity remains controversial. Intensive studies have revealed the essential role of mRNA on plant systemic signaling. We hypothesize that PS mRNA can act as a transmissible signal in tomato. Herein, we demonstrated that transgenic PS mRNA occurs in leaves located at considerable distances from the initial site of its generation by a transient Agrobacterium-infiltration assay system. We also showed that PS protein is present in the vascular bundle of the distant leaves. Our results indicate that transgenic PS mRNA may be functional as a long-distance signal to modulate systemic defense responses in tomato, providing novel insights into the multifaceted systems by which SYS signaling transports.
Highlights
Plants respond to mechanical wounding, herbivore injury or pathogen infection by induction of multiple protective genes throughout the whole plant as a defense against the invasion
Prosystemin (PS) mRNA was exclusively present in the vascular bundle in wounded or methyl jasmonate-treated leaves of tomato (Jacinto et al, 1997)
We hypothesized that the localization of PS mRNA may help its load into the phloem, where it could be readily transported throughout the plant
Summary
Plants respond to mechanical wounding, herbivore injury or pathogen infection by induction of multiple protective genes throughout the whole plant as a defense against the invasion. Wildtype (WT) plants grafted as scions onto transgenic rootstalks that constitutively express the PS sense gene accumulate high levels of defense proteins in the absence of wounding, suggesting that a systemic signal is produced by the transgenic rootstocks and is transported to the WT scions (McGurl et al, 1994).
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