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bioRxiv · 10.1101/2025.03.10.642428

A pennycress transparent testa 8 knockout mutant has drastic changes in seed coat anatomy and chemical compositions

Ding, X.·Duckworth, S.·Southworth, M.·Gautam, B.·Lipton, A.·Velickovic, D.·Sedbrook, J. C.·Handakumbura, P.
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Abstract

Pennycress is a winter annual intermediate crop with approximately 30% seed oil content suitable for producing biofuels. Here, we evaluated seed development, anatomy, and agronomically relevant traits of a transparent testa 8 knockout mutant (tt8-2bp) generated by CRISPR genome editing to improve seed quality. We performed histochemical analyses on wild-type and tt8-2bp seeds at different developmental stages. No visible anatomical defects were observed in embryos and endosperm of tt8-2bp seeds. However, tt8-2bp seed coats completely lost proanthocyanidins which were accumulated in an inner integument cell layer and in the thickened cell wall of an outer integument cell layer of wild-type seed coats. Based on spatial metabolomic and solid-state NMR analyses, tt8-2bp seed coats had decreased aromatic compounds and cell wall polysaccharides compared to wild-type seed coats. Additionally, tt8-2bp seeds had reduced seed coat dry weights and increased embryo dry weights compared to wild-type seeds, indicating changes in macronutrient partitioning during seed development. Mature tt8-2bp seeds exhibited increased imbibition rates and seed coat permeability to water-soluble molecules, suggesting a higher seed coat hydrophilicity than wild-type seeds. In conclusion, we did not find defects in tt8-2bp mutant seeds that were unfavorable agronomically, supporting that TT8 is an attractive target for pennycress domestication. HighlightHistochemical analyses of pennycress seeds revealed a complete loss of proanthocyanidins in tt8-2bp seed coats accompanied by increased seed imbibition rates and seed coat permeability compared to wild-type seeds.

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Ding, X., Duckworth, S., Southworth, M., Gautam, B., Lipton, A., Velickovic, D., Sedbrook, J. C., Handakumbura, P.. 2025-03-13. A pennycress transparent testa 8 knockout mutant has drastic changes in seed coat anatomy and chemical compositions. https://doi.org/10.1101/2025.03.10.642428

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