Exploring the role of the LkABCG36 transporter in lignin accumulation.

Lignin is a complex biopolymer formed through the condensation of three monomeric precursors known as monolignols. However, the mechanism underlying lignin precursor transport remains elusive, with uncertainty over whether it occurs through passive diffusion or an active energized process. ATP-binding cassette 36 (ABCG36) plays important roles in abiotic stress resistance. In this study, we investigated the transport functions of LkABCG36 (Larix kaempferi) for lignin precursors and the potential effects of LkABCG36 overexpression in plants. LkABCG36 enhanced the ability of tobacco (Nicotiana tabacum) bright yellow-2 (BY-2) cells to resist monolignol alcohol stress. Furthermore, LkABCG36 overexpression promoted lignin deposition in tobacco plant stem tissue. To understand the underlying mechanism, we measured the BY-2 cell ability to export lignin monomers and the uptake of monolignol precursors in inside-out (inverted) plasma membrane vesicles. We found that the transport of coniferyl and sinapyl alcohols is an ATP-dependent process. Our data suggest that LkABCG36 contributes to lignin accumulation in tobacco stem tissues through a mechanism involving the active transport of lignin precursors to the cell wall. These findings shed light on the lignin biosynthesis process, with important implications for enhancing lignin deposition in plants, potentially leading to improved stress tolerance and biomass production.

Transcriptomic Insights into Functions of LkABCG36 and LkABCG40 in Nicotiana tabacum.

ATP-binding cassette transporters (ABC transporters) play crucial physiological roles in plants, such as being involved in the growth and development of organs, nutrient acquisition, response to biotic and abiotic stress, disease resistance, and the interaction of the plant with its environment. The ABCG subfamily of proteins are involved in the process of plant vegetative organ development. In contrast, the functions of the ABCG36 and ABCG40 transporters have received considerably less attention. Here, we investigated changes in the transcriptomic data of the stem tissue of transgenic tobacco (Nicotiana tabacum) with LkABCG36 and LkABCG40 (Larix kaempferi) overexpression, and compared them with those of the wild type (WT). Compared with the WT, we identified 1120 and 318 differentially expressed genes (DEGs) in the LkABCG36 and LkABCG40 groups, respectively. We then annotated the function of the DEGs against the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The results showed enrichment in cell wall biogenesis and hormone signal transduction functional classes in transgenic LkABCG36 tobacco. In transgenic LkABCG40 tobacco, the enrichment was involved in metabolic and biosynthetic processes, mainly those related to environmental adaptation. In addition, among these DEGs, many auxin-related genes were significantly upregulated in the LkABCG36 group, and we found key genes involved in environmental adaptation in the LkABCG40 group, including an encoding resistance protein and a WRKY transcription factor. These results suggest that LkABCG36 and LkABCG40 play important roles in plant development and environmental adaptation. LkABCG36 may promote plant organ growth and development by increasing auxin transport, whereas LkABCG40 may inhibit the expression of WRKY to improve the resistance of transgenic tobacco. Our results are beneficial to researchers pursuing further study of the functions of ABCG36 and ABCG40.