School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
Graduate School of Agriculture, Ehime University, Matsuyama, Japan; Japan Science and Technology, PRESTO, Kawaguchi, Japan.
Curr Biol. 2022 Aug 22;32(16):3593-3600.e3. doi: 10.1016/j.cub.2022.06.063. Epub 2022 Jul 14.
There has been a dramatic recent increase in the understanding of the mechanisms by which plants detect their neighbors, including by touch, reflected light, volatile organic chemicals, and root exudates. The importance of root exudates remains ill-defined because of confounding experimental variables and difficulties disentangling neighbor detection in shoot and roots. There is evidence that root exudates allow distinction between kin and non-kin neighbors, but identification of specific exudates that function in neighbor detection and/or kin recognition remain elusive. Strigolactones (SLs), which are exuded into the soil in significant quantities in flowering plants to promote recruitment of arbuscular mycorrhizal fungi (AMF), seem intuitive candidates to act as plant-plant signals, since they also act as hormones in plants, with dramatic effects on shoot growth and milder effects on root development. Here, using pea, we test whether SLs act as either cues or signals for neighbor detection. We show that peas detect neighbors early in the life cycle through their root systems, resulting in strong changes in shoot biomass and branching, and that this requires SL biosynthesis. We demonstrate that uptake and detection of SLs exuded by neighboring plants are needed for this early neighbor detection, and that plants that cannot exude SLs are outcompeted by neighboring plants and fail to adjust growth to their soil volume. We conclude that plants both exude SLs as signals to modulate neighbor growth and detect environmental SLs as a cue for neighbor presence; collectively, this allows plants to proactively adjust their shoot growth according to neighbor density.
近年来，人们对植物如何感知其周围环境（包括通过触摸、反射光、挥发性有机化学物质和根系分泌物）的机制有了更深入的了解。由于实验变量的干扰和区分地上部和根系中邻居检测的困难，根系分泌物的重要性仍然难以确定。有证据表明，根系分泌物可以区分亲缘关系和非亲缘关系的邻居，但识别在邻居检测和/或亲缘识别中起作用的特定分泌物仍然难以捉摸。独脚金内酯（SLs）是开花植物在土壤中大量分泌的物质，以促进丛枝菌根真菌（AMF）的招募，它们似乎是作为植物-植物信号的直观候选物，因为它们在植物中也作为激素发挥作用，对地上部生长有显著影响，对根系发育的影响较小。在这里，我们使用豌豆来测试 SLs 是否作为邻居检测的线索或信号。我们发现，豌豆通过根系在生命周期早期就能感知到邻居的存在，从而导致地上部生物量和分枝的强烈变化，而这需要 SL 的生物合成。我们证明，对邻株分泌的 SLs 的吸收和检测是早期邻居检测所必需的，而无法分泌 SLs 的植物会被邻株竞争淘汰，并且无法根据土壤体积调整生长。我们得出结论，植物既分泌 SLs 作为信号来调节邻居的生长，又能检测环境中的 SLs 作为邻居存在的线索；总的来说，这使得植物能够根据邻居的密度主动调整地上部的生长。
