Carlactone-independent seedling morphogenesis in Arabidopsis
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Strigolactone hormones are derived from carotenoids via carlactone, and act through the α/β–hydrolase D14 and the F–box protein D3/MAX2 to repress plant shoot branching. While MAX2 is also necessary for normal seedling development, D14 and the known strigolactone biosynthesis genes are not, raising the question of whether endogenous, canonical strigolactones derived from carlactone have a role in seedling morphogenesis. Here, we report the chemical synthesis of the strigolactone precursor carlactone, and show that it represses Arabidopsis shoot branching and influences leaf morphogenesis via a mechanism that is dependent on the cytochrome P450 MAX1. In contrast, both physiologically active Z–carlactone and the non-physiological E isomer exhibit similar weak activity in seedlings, and predominantly signal through D14 rather than its paralogue KAI2, in a MAX2-dependent but MAX1-independent manner. KAI2 is essential for seedling morphogenesis, and hence this early-stage development employs carlactone-independent morphogens for which karrikins from wildfire smoke are specific surrogates. While the commonly employed synthetic strigolactone GR24 acts non-specifically through both D14 and KAI2, carlactone is a specific effector of strigolactone signalling that acts through MAX1 and D14.
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Specialisation within the DWARF14 protein family confers distinct responses to karrikins and strigolactones in ArabidopsisWaters, M.; Nelson, D.; Scaffidi, A.; Flematti, G.; Sun, Y.; Dixon, Kingsley; Smith, S. (2012)Karrikins are butenolides derived from burnt vegetation that stimulate seed germination and enhance seedling responses to light. Strigolactones are endogenous butenolide hormones that regulate shoot and root architecture, ...
Nelson, D.; Flematti, G.; Ghisalberti, E.; Dixon, Kingsley; Smith, S. (2012)It is well known that burning of vegetation stimulates new plant growth and landscape regeneration. The discovery that char and smoke from such fires promote seed germination in many species indicates the presence of ...
Nelson, D.; Scaffidi, A.; Dun, E.; Waters, M.; Flematti, G.; Dixon, Kingsley; Beveridge, C.; Ghisalberti, E.; Smith, S. (2011)Smoke is an important abiotic cue for plant regeneration in postfire landscapes. Karrikins are a class of compounds discovered in smoke that promote seed germination and influence early development of many plants by an ...