Karrikins are small butenolide molecules with the capacity to promote germination and enhance seedling establishment. Generated abiotically from partial combustion of vegetation, karrikins are comparatively rare in the environment, but studying their mode of action has been most informative in revealing a new regulatory pathway for plant development that uses the karrikin perception machinery. Recent studies suggest that the karrikin receptor protein KAI2 and downstream transcriptional co-repressors in the SMXL family influence seed germination, seedling photomorphogenesis, root morphology, and responses to abiotic stress such as drought. Based on taxonomic distribution, this pathway is ubiquitous and likely to be evolutionarily ancient, originating prior to land plants. However, we still do not have a good grasp on how karrikins actually activate the receptor protein, and we have yet to discover the assumed endogenous ligand for KAI2 that karrikins are thought to mimic. This review covers recent progress in this field, as well as current gaps in our knowledge.

中文翻译：

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植物对karrikins的感知：一个持续的谜团。

Karrikins是丁烯酸内酯的小分子，具有促进发芽和增强幼苗生长的能力。karrikins是由植物的部分燃烧非生物产生的，在环境中相对很少见，但是研究其作用方式在揭示使用karrikin感知机制的植物发育的新调控途径方面最有指导意义。最近的研究表明，SMXL家族中的karrikin受体蛋白KAI2和下游转录共阻遏物影响种子发芽，幼苗光形态发生，根形态以及对非生物胁迫（如干旱）的反应。根据分类学分布，该途径无处不在，可能在进化上古老，起源于陆地植物。然而，我们仍然不了解karrikins如何实际激活受体蛋白，并且我们还没有发现karrikins被模仿的假定的KAI2内源性配体。这篇综述涵盖了该领域的最新进展以及我们目前的知识差距。