Drought is a common abiotic stress for terrestrial plants and often affects crop development and yield. Recent studies have suggested that lignin plays a crucial role in plant drought tolerance; however, the underlying molecular mechanisms are still largely unknown. Here, we report that the rice (Oryza sativa) gene CINNAMOYL-CoA REDUCTASE 10 (OsCCR10) is directly activated by the OsNAC5 transcription factor, which mediates drought tolerance through regulating lignin accumulation. CCR is the first committed enzyme in the monolignol synthesis pathway, and the expression of 26 CCR genes was observed to be induced in rice roots under drought. Subcellular localisation assays revealed that OsCCR10 is a catalytically active enzyme that is localised in the cytoplasm. The OsCCR10 transcript levels were found to increase in response to abiotic stresses, such as drought, high salinity, and abscisic acid (ABA), and transcripts were detected in roots at all developmental stages. In vitro enzyme activity and in vivo lignin composition assay suggested that OsCCR10 is involved in H-and G-lignin biosynthesis. Transgenic rice plants overexpressing OsCCR10 showed improved drought tolerance at the vegetative stages of growth, as well as higher photosynthetic efficiency, lower water loss rates, and higher lignin content in roots compared to non-transgenic (NT) controls. In contrast, CRISPR/Cas9-mediated OsCCR10 knockout mutants exhibited reduced lignin accumulation in roots and less drought tolerance. Notably, transgenic rice plants with root-preferential overexpression of OsCCR10 exhibited higher grain yield than NT controls plants under field drought conditions, indicating that lignin biosynthesis mediated by OsCCR10 contributes to drought tolerance.
In this study, kraft lignin was used
as a polymer for drug-encapsulated
nanoparticle synthesis (coumarin 6 and doxorubicin; DOX). Successful
drug encapsulation by nanoprecipitation was confirmed (max. 59% for
coumarin 6 and max. 73% for DOX). Compared with the pure lignin nanoparticle,
drug-encapsulated nanoparticles showed no remarkable change in their
size (i.d. 176–469 nm) and surface charge (−40.5 to
−32.7 mV) regardless of the drug in the particle. The drug-release
profiles of the particles showed that they follow the Fickian diffusion. In vitro cytotoxicity assay revealed that the drug-release
effect of DOX-encapsulated nanoparticles was delayed but the anticancer
activity was not decreased. In addition, the hemocompatibility test, in vivo allergic reaction test, and tumor inhibition assays
using tumors in mice showed high biocompatibility of the lignin-based
drug delivery system and reduced side effects during chemotherapy.
This study suggests that kraft lignin has great potential as an eco-friendly
and economically sustainable drug delivery system.
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