Elucidating the signaling mechanism of strigolactones has been the key to controlling the devastating problem caused by the parasitic plant Striga hermonthica. To overcome the genetic intractability that has previously interfered with identification of the strigolactone receptor, we developed a fluorescence turn-on probe, Yoshimulactone Green (YLG), which activates strigolactone signaling and illuminates signal perception by the strigolactone receptors. Here we describe how strigolactones bind to and act via ShHTLs, the diverged family of α/β hydrolase-fold proteins in Striga. Live imaging using YLGs revealed that a dynamic wavelike propagation of strigolactone perception wakes up Striga seeds. We conclude that ShHTLs function as the strigolactone receptors mediating seed germination in Striga. Our findings enable access to strigolactone receptors and observation of the regulatory dynamics for strigolactone signal transduction in Striga.

The phytohormone auxin, indole-3-acetic acid (IAA), regulates nearly all aspects of plant growth and development. Despite substantial progress in our understanding of auxin biology, delineating specific auxin response remains as a major challenge. Auxin regulates transcriptional response via its receptors, TIR1/AFB F-box proteins. Here we report an engineered, orthogonal auxin-TIR1 receptor pair, developed through a bump-and-hole strategy, that triggers auxin signaling without interfering with endogenous auxin or TIR1/AFBs. A synthetic, convex IAA (cvxIAA) hijacked the downstream auxin signaling in vivo both at the transcriptomic level and in specific developmental contexts, only in the presence of a complementary, concave TIR1 (ccvTIR1) receptor. Harnessing the cvxIAA-ccvTIR1 system, we provide conclusive evidence for the role of TIR1-mediated pathway in auxin-induced seedling acid growth. The cvxIAA-ccvTIR1 system serves as a powerful tool for solving outstanding questions in auxin biology and for precise manipulation of auxin-mediated processes as a controllable switch.

Aromaticity of photoexcited molecules is an important concept in organic chemistry. Its theory, Baird's rule for triplet aromaticity since 1972 gives the rationale of photoinduced conformational changes and photochemical reactivities of cyclic π-conjugated systems. However, it is still challenging to monitor the dynamic structural change induced by the excited-state aromaticity, particularly in condensed materials. Here we report direct structural observation of a molecular motion and a subsequent packing deformation accompanied by the excited-state aromaticity. Photoactive liquid crystal (LC) molecules featuring a π-expanded cyclooctatetraene core unit are orientationally ordered but loosely packed in a columnar LC phase, and therefore a photoinduced conformational planarization by the excited-state aromaticity has been successfully observed by time-resolved electron diffractometry and vibrational spectroscopy. The structural change took place in the vicinity of excited molecules, producing a twisted stacking structure. A nanoscale torque driven by the excited-state aromaticity can be used as the working mechanism of new photoresponsive materials.

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Strigolactones are phytohormones, which affect diverse aspects of plant growth and development with potential application in modern agriculture. Recently, heliolactone has been isolated as a non‐canonical type of strigolactone from the root exudates of sunflower, and it could be involved in signaling in the rhizosphere as well as in planta. However, its biological activity is yet to be evaluated, due to its relative chemical instability and its low natural abundance. Herein, we describe the gram‐scale synthesis of heliolactone and its derivatives by using Stille cross‐coupling as the key bond‐forming reaction, and we disclose some of their biological activities (soil stability, binding ability to strigolactone receptor, corn germination, sunflower germination, Orobanche cumana germination and leaf senescence) in comparison with other canonical and non‐canonical strigolactones.