Genome-wide analysis of UGDH genes in Populus trichocarpa and responsiveness to nitrogen treatment

Network Analysis of Metabolome and Transcriptome Revealed Regulation of Different Nitrogen Concentrations on Hybrid Poplar Cambium Development

Secondary development is a key biological characteristic of woody plants and the basis of wood formation. Exogenous nitrogen can affect the secondary growth of poplar, and some regulatory mechanisms have been found in the secondary xylem. However, the effect of nitrogen on cambium has not been reported. Herein, we investigated the effects of different nitrogen concentrations on cambium development using combined transcriptome and metabolome analysis. The results show that, compared with 1 mM NH4NO3 (M), the layers of hybrid poplar cambium cells decreased under the 0.15 mM NH4NO3 (L) and 0.3 mM NH4NO3 (LM) treatments. However, there was no difference in the layers of hybrid poplar cambium cells under the 3 mM NH4NO3 (HM) and 5 mM NH4NO3 (H) treatments. Totals of 2365, 824, 649 and 398 DEGs were identified in the M versus (vs.) L, M vs. LM, M vs. HM and M vs. H groups, respectively. Expression profile analysis of the DEGs showed that exogenous nitrogen affected the gene expression involved in plant hormone signal transduction, phenylpropanoid biosynthesis, the starch and sucrose metabolism pathway and the ubiquitin-mediated proteolysis pathway. In M vs. L, M vs. LM, M vs. HM and M vs. H, differential metabolites were enriched in flavonoids, lignans, coumarins and saccharides. The combined analysis of the transcriptome and metabolome showed that some genes and metabolites in plant hormone signal transduction, phenylpropanoid biosynthesis and starch and sucrose metabolism pathways may be involved in nitrogen regulation in cambium development, whose functions need to be verified. In this study, from the point of view that nitrogen influences cambium development to regulate wood formation, the network analysis of the transcriptome and metabolomics of cambium under different nitrogen supply levels was studied for the first time, revealing the potential regulatory and metabolic mechanisms involved in this process and providing new insights into the effects of nitrogen on wood development.

Identification and expression analysis of the PtGATL genes under different nitrogen and carbon dioxide treatments in Populus trichocarpa

Pectin is one of the most important components of the plant cell wall. Galacturonosyltransferase-like (GATL) is an important enzyme involved in forming pectin in Arabidopsis thaliana. In this study, 12 PtGATL genes were identified and characterized based on the Populus trichocarpa genome using bioinformatics methods. The results showed that the PtGATLs contained four typical motifs, including DXD, LPPF, GLG, and HXXGXXKPW. According to phylogenetic analysis, PtGATLs were divided into six groups. Chromosome distribution and genome synteny analysis showed that there were 11 segmental-duplicated gene pairs with repeated fragments on chromosomes 2, 5, 7, 8, 10, and 14. Tissue-specific expression profiles indicated that these PtGATLs had different expression patterns. The transcription level of PtGATLs was regulated by different carbon dioxide and nitrogen concentrations. In conclusion, the identification and analysis of PtGATL genes in poplar provide important information on the gene function.

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The online version contains supplementary material available at 10.1007/s13205-022-03129-y.

ARPI, β-AS, and UGE regulate glycyrrhizin biosynthesis in Glycyrrhiza uralensis hairy roots

ARPI, β-AS, and UGE were cloned from G. uralensis and their regulatory effects on glycyrrhizin biosynthesis were investigated. β-AS and UGE but not ARPI positively regulate the biosynthesis of glycyrrhizin. Glycyrrhiza uralensis Fisch. has been used to treat respiratory, gastric, and liver diseases since ancient China. The most important and widely studied active component in G. uralensis is glycyrrhizin (GC). Our pervious RNA-Seq study shows that GC biosynthesis is regulated by multiple biosynthetic pathways. In this study, three target genes, ARPI, β-AS, and UGE from different pathways were selected and their regulatory effects on GC biosynthesis were investigated using G. uralensis hairy roots. Our data show that hairy roots knocking out ARPI or UGE died soon after induction, indicating that the genes are essential for the growth of G. uralensis hairy roots. Hairy roots with β-AS knocked out grew healthily. However, they failed to produce GC, suggesting that β-AS is required for triterpenoid skeleton formation. Conversely, overexpression of UGE or β-AS significantly increased the GC content, whereas overexpression of ARPI had no obvious effects on GC accumulation in G. uralensis hairy roots. Our findings demonstrate that β-AS and UGE positively regulate the biosynthesis of GC.