Canonical Ru(ii) tris-polypyridyl complexes as confocal-compatible stains for lignified secondary-wall domains in Arabidopsis thaliana stems.

Abstract

Fluorescent stains for lignified plant walls must operate in chemically heterogeneous, autofluorescent matrices while remaining compatible with confocal multiplexing. Here, we evaluated two canonical Ru(ii) tris-polypyridyl luminophores, Ru1 ([Ru(deeb) 3 ] 2+ ) and Ru2 ([Ru(phen) 3 ] 2+ ), as non-derivatizing stains for fixed Arabidopsis thaliana stem sections. In situ spectral profiling defined practical 405-nm confocal detection windows, and both probes produced reproducible wall-associated photoluminescence enriched in secondary-wall-rich vascular domains, especially xylem vessels and interfascicular fibers. Their anatomical distribution showed qualitative concordance with Wiesner/Mäule lignin histochemistry and condition-validated Safranin O maps, supporting their use as spatial reporters of matrix-associated enrichment within anatomically defined lignified secondary-wall territories. The molecular determinants of this enrichment, including the relative contribution of lignin and other wall polymers, remain to be resolved. Sequential co-staining with Calcofluor White separated broad β-glucan-rich wall architecture from Ru-enriched secondary-wall domains, while spectral-overlap analysis identified far-red Alexa Fluor 647 excitation at 638 nm as the most orthogonal tested third-label configuration. Ligand-comparative DFT descriptors provided structure-property fingerprints summarizing differences in π-surface continuity and electrostatic anisotropy. Overall, these results position canonical Ru(ii) polypyridyl luminophores as confocal-compatible, chemically tractable scaffolds for anatomical imaging of lignified plant-wall territories.

Plant phenotyping relevance

植物の木化二次細胞壁を可視化・空間評価する共焦点蛍光染色法の開発と検証が中心であり、単なる生物学的測定ではない。

Code and data availability

The article states all supporting data are in the article and its supplementary information (spectroscopy, DFT descriptor figures, microscopy images, Table S1), but no public repository deposit, dataset, image collection, or author analysis code with an explicit public URL is provided. The SI is attached to the article

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