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4-Coumarate: coenzyme A ligase (4CL; EC 6.2.1.12) is an important enzyme in the phenylpropanoid metabolic pathway that controls the biosynthesis of lignin and flavonoids. In this study, to identify the function of the Ag4CL3 gene of celery, the Ag4CL3 gene was cloned from celery cv. "Nanxuan Liuhe Ziqin". Sequence analysis results showed that the Ag4CL3 gene contained an open reading frame (ORF) with a length of 1688 bp, and 555 amino acids were encoded. The Ag4CL3 protein was highly conserved among different plant species. Phylogenetic analysis demonstrated that the 4CL proteins from celery and carrot belonged to the same clade. The Ag4CL3 protein was mainly composed of 31.89% α-helixes, 18.02% extended strands, 6.67% β-turns, and 43.42% random coils, and the signal peptide was unfound. A total of 62 phosphorylation sites and a class-I superfamily of adenylate-forming domains were found. As the growth time increased, the plant height and stem thickness also increased, and the petiole lignin content increased and became lignified gradually. The relative expression levels of the Ag4CL3 gene in "Nanxuan Liuhe Ziqin" petioles were higher than those in other tissues, with the highest level occurring 70 d after sowing. The lignin contents in the transgenic Arabidopsis thaliana lines hosting the Ag4CL3 gene were higher than those in the WT. In this study, the overexpression of Ag4CL3 led to the significant upregulation of lignin biosynthesis gene expression in transgenic A. thaliana plants, except for AtPAL, AtCCR, and AtLAC. This study speculates that Ag4CL3 genes are related to lignin synthesis in A. graveolens. [ABSTRACT FROM AUTHOR]

The characteristics of anthocyanin and lignin are important parameters in evaluating the quality of red Toona sinensis buds. Red T. sinensis buds are prone to senescence during postharvest storage, which subsequently affects their quality and sales. However, the mechanism of senescence in red T. sinensis buds under low-temperature conditions remains unclear. In this study, red T. sinensis buds were stored at 4 °C, and their anthocyanin and lignin contents as well as the enzyme activities of PAL (phenylalanine ammonia lyase), 4CL (4-coumarate-CoA ligase), CAD (cinnamyl alcohol dehydrogenase) and POD (peroxidase) were determined at 0, 1, 2 and 3 d after handing. Meanwhile, the cellular structure of postharvest red T. sinensis buds was observed by microscopy. The relative expression of lignin-related and anthocyanin-related genes was analyzed using qRT-PCR. The results show that the anthocyanin content of the leaves was higher than that of the petioles. After 3 d of storage, the anthocyanin content of the leaves was 4.66 times that of the petioles. Moreover, the lignin content of the red T. sinensis buds gradually increased. Compared with 0 d, the lignin content of the leaves and petioles increased by 331.8 and 94.14 mg·g−1, respectively. The enzyme activities of PAL, 4CL, CAD and POD increased during cold storage. The intercellular space and the arrangement of the palisade tissue and sponge tissue in the mesophyll of red T. sinensis buds became smaller and closer, respectively. The secondary cell wall of xylem cells thickened, the number of xylem cells increased, and the arrangement number of the xylem cells became closed in the leaf vein and petioles during red T. sinensis bud storage. The expression levels of anthocyanin-related (Except for TsCHS and TsANS) and lignin-related genes increased during red T. sinensis bud storage and are highly consistent with the accumulation patterns of anthocyanins and lignin. This study may serve as a reference for exploring the molecular mechanisms of senescence, regulating the quality and cultivating new varieties of red T. sinensis buds that have low lignin content but high anthocyanin content after harvest. [ABSTRACT FROM AUTHOR]

The NAC transcription factor participates in various biotic and abiotic stress responses and plays a critical role in plant development. Lignin is a water-insoluble dietary fiber, but it is second only to cellulose in abundance. Celery is the main source of dietary fiber, but its quality and production are limited by various abiotic stresses. Here, AgNAC1 containing the NAM domain was identified from celery. AgNAC1 was found to be a nuclear protein. Transgenic Arabidopsis thaliana plants hosting AgNAC1 have longer root lengths and stomatal axis lengths than the wide type (WT). The evidence from lignin determination and expression levels of lignin-related genes indicated that AgNAC1 plays a vital role in lignin biosynthesis. Furthermore, the results of the physiological characterization and the drought and salt treatments indicate that AgNAC1 -overexpressing plants are significantly resistive to salt stress. Under drought and salt treatments, the AgNAC1 transgenic Arabidopsis thaliana plants presented increased superoxide dismutase (SOD) and peroxidase (POD) activities and decreased malondialdehyde (MDA) content and size of stomatal apertures relatively to the WT plants. The AgNAC1 served as a positive regulator in inducing the expression of stress-responsive genes. Overall, the overexpressing AgNAC1 enhanced the plants' resistance to salt stress and played a regulatory role in lignin accumulation. • AgNAC1 was a protein located in the nucleus. • Overexpression of AgNAC1 enhanced the drought resistance and salt tolerance. • Overexpression of AgNAC1 promoted lignin accumulation and lignin-related genes expression under salt stress. [ABSTRACT FROM AUTHOR]

Water dropwort (Oenanthe sinensis Dunn, 2 n = 42) is a kind of aquatic vegetable rich in nutrients. Here, we present a high-quality assembly and analysis of the water dropwort genome. A total of 990.83 Mb genome assembly was anchored into 21 chromosomes using the combined technologies, including PacBio-CCS (HiFi), second generation Illumina sequencing, and Hi-C technologies. Obtained contig N50 length is 47.67 Mb. In total, 54,711 protein-coding genes in O. sinensis genome were annotated. In addition to the γ triplication event shared by eudicots, water dropwort underwent three rounds of whole-genome duplication (WGD) event. We characterized an additional polyploidization that occurred after the divergence of O. sinensis from the other three members of Apiaceae family, carrot, celery, and coriander, clarifying the chromosome evolutionary trajectory among these Apiaceae plants with known reference genome. WGD event have contributed to the expansion of gene families, including those with roles in cellulose and lignin biosynthesis. WGCNA analysis suggested that Os0507490.1 (OsG8H) played a potential role in cellulose and lignin metabolisms. The current data provided a valuable resource for accelerating molecular breeding programs of water dropwort and shed novel light on its genomic evolution, as well as the modulation of cellulose and lignin biosynthesis. [Display omitted] • A chromosome-scale assembly of the water dropwort genome was first reported here. • Assembled O. sinensis genome provided insights into genome evolution of Apiaceae. • A young polyploidization was occurred in O. sinensis. • Os0507490.1 (OsG8H) played a potential role in cellulose and lignin metabolisms. [ABSTRACT FROM AUTHOR]