Morphologically and physiologically diverse fruits of two Lepidium species differ in allocation of glucosinolates into immature and mature seed and pericarp

Abstract

The morphology and physiology of diaspores play crucial roles in determining the fate of seeds in unpredictable habitats. In some genera of the Brassicaceae different types of diaspores can be found.Lepidium appelianumproduces non-dormant seeds within indehiscent fruits while inL.campestredormant seeds are released from dehiscent fruits. We investigated whether the allocation of relevant defence compounds into different tissues in differentLepidiumspecies may be related to the diverse dispersal strategy (indehiscent and dehiscent) and seed physiology (non-dormant and dormant). Total glucosinolate concentration and composition were analysed in immature and mature seeds and pericarps ofL.appelianumandL.campestreusing high-performance liquid chromatography. Moreover, for comparison, transgenic RNAiL.campestrelines were used that produce indehiscent fruits due to silencing ofLcINDEHISCENCE, theINDEHISCENCEortholog ofL.campestre. Total glucosinolate concentrations were lower in immature compared to mature seeds in all studiedLepidiumspecies and transgenic lines. In contrast, indehiscent fruits ofL.appelianummaintained their total glucosinolate concentration in mature pericarps compared to immature ones, while in dehiscentL.campestreand in indehiscent RNAi-LcIND L.campestrea significant decrease in total glucosinolate concentrations from immature to mature pericarps could be detected. Indole glucosinolates were detected in lower abundance than the other glucosinolate classes (aliphatic and aromatic). Relatively high concentrations of 4-methoxyindol-3-ylmethyl glucosinolate were found in mature seeds ofL.appelianumcompared to other tissues, while no indole glucosinolates were detected in mature diaspores ofL.campestre. The diaspores of the latter species may rather depend on aliphatic and aromatic glucosinolates for long-term protection. The allocation patterns of glucosinolates correlate with the morpho-physiologically distinct fruits ofL.appelianumandL.campestreand may be explained by the distinct dispersal strategies and the dormancy status of both species.