To gain better insight into the regulatory networks of anthocyanin biosynthesis, an integrated analysis of the metabolome and transcriptome in purple and green leaves of Tetrastigma hemsleyanum was conducted. Transcript and metabolite profiles were archived by RNA-sequencing data analysis and LC-ESI-MS/MS, respectively. There were 209 metabolites and 4211 transcripts that were differentially expressed between purple and green leaves. Correlation tests of anthocyanin contents and transcriptional changes showed 141 significant correlations (Pearson correlation coefficient >0.8) between 16 compounds and 14 transcripts involved in the anthocyanin biosynthesis pathway. Some novel genes and metabolites were discovered as potential candidate targets for the improvement of anthocyanin content and superior cultivars.

Nanotechnology is one of the most recent approaches employed to defend plants against both biotic and abiotic stress including heavy metals such as Cadmium (Cd). In this study, we evaluated the effects of titanium dioxide (TiO₂) nanoparticles (TiO₂ NPs) in alleviating Cd stress in Tetrastigma hemsleyanum Diels et Gilg. Compared with Cd treatment, TiO₂ NPs decreased leaf Cd concentration, restored Cd exposure-related reduction in the biomass to about 69% of control and decreased activities of antioxidative enzymes. Integrative analysis of transcriptome and metabolome revealed 325 differentially expressed genes associated with TiO₂ NP treatment, most of which were enriched in biosynthesis of secondary metabolites. Among them, the flavonoid and phenylpropanoid biosynthetic pathways were significantly regulated to improve the growth of T. hemsleyanum when treated with Cd. In the KEGG Markup Language (KGML) network analysis, we found some commonly regulated pathways between Cd and Cd+TiO₂ NP treatment, including phenylpropanoid biosynthesis, ABC transporters, and isoflavonoid biosynthesis, indicating their potential core network positions in controlling T. hemsleyanum response to Cd stress. Overall, our findings revealed a complex response system for tolerating Cd, encompassing the transportation, reactive oxygen species scavenging, regulation of gene expression, and metabolite accumulation in T. hemsleyanum. Our results indicate that TiO₂ NP can be used to reduce Cd toxicity in T. hemsleyanum.

Small fructans improve plant tolerance for cold stress. However, the underlying molecular mechanisms are poorly understood. Here, we have demonstrated that the small fructan tetrasaccharide nystose improves the cold stress tolerance of primary rice roots. Roots developed from seeds soaked in nystose showed lower browning rate, higher root activity, and faster growth compared to seeds soaked in water under chilling stress. Comparative proteomics analysis of nystose-treated and control roots identified a total of 497 differentially expressed proteins. GO classification and KEGG pathway analysis documented that some of the upregulated differentially expressed proteins were implicated in the regulation of serine/threonine protein phosphatase activity, abscisic acid-activated signaling, removal of superoxide radicals, and the response to oxidative stress and defense responses. Western blot analysis indicated that nystose promotes the growth of primary rice roots by increasing the level of RSOsPR10, and the cold stress-induced change in RSOsPR10levelis regulated by jasmonate, salicylic acid, and abscisic acid signaling pathways in rice roots. Furthermore, OsMKK4-dependentmitogen-activated protein kinase signaling cascades may be involved in the nystose-induced cold tolerance of primary rice roots. Together, these results indicate that nystose acts as an immunostimulator of the response to cold stress by multiple signaling pathways.

Tetrastigma hemsleyanum Diels et Gilg is a rare and wild medicinal resource. Metabolites, especially secondary metabolites, have an important influence on T. hemsleyanum adaptability and its medicinal quality. The metabolite proanthocyanidin (PA) is a polyphenol compound widely distributed in land plants, which can be used as antioxidants and anticancer agents. Here, we discovered that three types of PA accumulated in large amounts in purple leaves (PL), but not in green leaves (RG), based on widely non-targeted metabolomics. In addition, we further found that catechins and their derivatives, which are the structural units of PA, are also enriched in PL. Afterwards, we screened and obtained five key genes, DNR1/2, ANS, ANR and LAR closely related to PA biosynthesis through transcriptome analysis and found they were all highly expressed in PL compared to RG. Therefore, observed the regulatory relationship between the main compounds and genes network, and the PA metabolism regulatory pathway was complicated, which may be different to other species.

Phosphite (PHI) has been used in the management of Phytophthora diseases since the 1970s.We assessed the effect of PHI on controlling the incidence of Xanthomonas oryzae pv.oryzae and Pyricularia grisea. As a result, PHI application significantly inhibited the incidence of the diseases. To clarify the molecular mechanism underlying this, a transcriptome study was employed. In total, 2064 differentially expressed genes (DEGs) were identified between control and PHI treatment. The key DEGs could be classified into phenylpropanoid biosynthesis (ko00940), starch and sucrose metabolism (ko00500), and plant hormone signal transduction (ko04075). The expressions of defense-related genes had a higher expression lever upon PHI treatment. This study provides new insights into the mechanism of protection effect of PHI against pathogens.

Tetrastigma hemsleyanum Diels et Gilg, commonly known as Sanyeqing (SYQ), is an important traditional Chinese medicine. The content of bioactive constituents varies in different cultivars of SYQ. In the plant growth related researches, rhizosphere microbiome has gained significant attention. However, the role of bacterial communities in the accumulation of metabolites in plants have not been investigated. Herein, the composition of bacterial communities in the rhizosphere soils and the metabolites profile of different SYQ cultivars’ roots were analyzed. It was found that the composition of microbial communities varied in the rhizosphere soils of different SYQ cultivars. The high abundance of Actinomadura, Streptomyces and other bacteria was found to be associated with the metabolites profile of SYQ roots. The findings suggest that the upregulation of rutin and hesperetin may contribute to the high bioactive constituent in SYQ roots. These results provide better understanding of the metabolite accumulation pattern in SYQ, and also provide a solution for enhancing the quality of SYQ by application of suitable microbial consortia.