Identification of Key Genes Associated with 1,2,6-Tri-O-galloyl-ß-D-glucopyranose Accumulation in Camellia sinensis Based on Transcriptome Sequencing.

Hydrolyzed tannin 1,2,6-tri-O-galloyl-ß-D-glucopyranose (1,2,6-TGGP) possesses significant medicinal properties. However, little is known about its underlying molecular mechanisms. In this study, the levels of 1,2,6-TGGP in tea materials from different cultivars and leaf positions were compared. Additionally, one leaf and one bud sample from six tea cultivars with significant variations in 1,2,6-TGGP levels were analyzed using transcriptome high-throughput sequencing to identify the genes that are responsible for 1,2,6-TGGP accumulation. The sequencing results were mapped to the reference tea genome, revealing a total of 2735 differentially expressed genes (DEGs). This set included four UDP glycosyltransferase (UGTs) and six serine carboxypeptidases-like (SCPLs) genes. Among them, the upregulated SCPLs (CSS0032817) may directly participate in the acylation reaction of 1,2,6-TGGP. In addition, several classes of DEGs, including cytochrome P450, were significantly associated with the 1,2,6-TGGP content, which is potentially involved in their regulation. Overall, these results provide new insights into the molecular mechanism of 1,2,6-TGGP accumulation.

Identification of a BAHD Acyltransferase Gene Involved in Plant Growth and Secondary Metabolism in Tea Plants.

Plant acyl-CoA dominated acyltransferases (named BAHD) comprise a large appointed protein superfamily and play varied roles in plant secondary metabolism like synthesis of modified anthocyanins, flavonoids, volatile esters, etc. Tea (Camellia sinensis) is an important non-alcoholic medicinal and fragrancy plant synthesizing different secondary metabolites, including flavonoids. In the tea (C.A sinensis) cultivar Longjing 43 (LJ43), eight samples were performed into three groups for transcriptome analysis under three biological replications. Among the BAHD acyltransferase genes in tea cultivars, the expression of TEA031065 was highest in buds and young leaves following the RNA sequencing data, which was coincident with the tissue rich in catechins and other flavonoids. We then transformed this gene into wild-type Arabidopsis as an over-expression (OX) line 1 and line 2 in ½ MS media to verify its function. In the wild types (WT), the primary root length, number of secondary roots, and total root weight were significantly higher at 24%, 15%, and 53.92%, respectively, compared to the transgenic lines (OX1 and OX2). By contrast, the leaves displayed larger rosettes (21.58%), with higher total leaf weight (32.64%) in the transgenic lines than in the wild type (WT). This result is consistent with DCR mutant At5g23940 gene in Arabidopsis thaliana. Here, anthocyanin content in transgenic lines was also increased (21.65%) as compared to WT. According to the RNA sequencing data, a total of 22 growth regulatory genes and 31 structural genes with TFs (transcription factors) that are correlative with plant growth and anthocyanin accumulation were identified to be differentially expressed in the transgenic lines. It was found that some key genes involved in IAA (Auxin) and GA (Gibberellin) biosynthesis were downregulated in the transgenic lines, which might be correlated with the phenotype changes in roots. Moreover, the upregulation of plant growth regulation genes, such as UGT73C4 (zeatin), ARR15, GH3.5, ETR2, ERS2, APH4, and SAG113 might be responsible for massive leaf growth. In addition, transgenic lines shown high anthocyanin accumulation due to the upregulation of the (1) 3AT1 and (3) GSTF, particularly, GSTF12 genes in the flavonoid biosynthesis pathway. However, the TFs such as, CCoAMT, bHLH, WRKY, CYP, and other MYBs were also significantly upregulated in transgenic lines, which increased the content of anthocyanins in A. thaliana seedlings. In conclusion, a BAHD acyltransferase (TEA031065) was identified, which might play a vital role in tea growth and secondary metabolites regulation. This study increases our knowledge concerning the combined functionality of the tea BAHD acyltransferase gene (TEA031065).

Responses of tea plants (Camellia sinensis) with different low-nitrogen tolerances during recovery from nitrogen deficiency.

BACKGROUND: Tea plants have high nitrogen (N) consumptions, whereas molecular and physiological responses of tea plants to N recovery are still unclear. RESULTS: By using non-invasive micro-test technology (NMT), 15 N tracer technique, ultra-performance liquid chromatography (UPLC), and transcriptome sequencing technology, we investigated the N recovery-induced changes in N absorptions, N tissue distributions, contents of free amino acids (FAAs), and global transcription of the low-N tolerant and intolerant tea genotypes [i.e. Wuniuzao (W) and Longjing43 (L)]. The results showed that the phenotype of Wuniuzao was better than that of Longjing43 under low-N condition. The N absorption and utilization of Wuniuzao were superior to Longjing43 under N recovery. The γ-aminobutyric acid (GABA) ratio (N recovery/N deficiency) in the root of Wuniuzao was significantly higher than that of Longjing43, while the glutamic acid ratio in the root of Wuniuzao was significantly lower than that of Longjing43. This findings suggested that Wuniuzao tended to enhance the GABA synthesis, while Longjing43 tended to inhibit the GABA synthesis under N recovery. The key genes in response to N recovery in Wuniuzao included N transport (AMT and NRT), N transformation (NR, NirA, and GAD), and amino acid transport (GAT) genes. In addition, some ribosome and flavonoid biosynthesis genes might help to maintain proteome homeostasis. CONCLUSION: The N absorption and transport, and the conversion abilities of key amino acids (Glu and GABA) might improve the adaptability of tea plants to N recovery, which provided a basis for the breeding of N efficient tea varieties. © 2021 Society of Chemical Industry.

Development of SNP Markers for Original Analysis and Germplasm Identification in Camellia sinensis.

Tea plants are widely grown all over the world because they are an important economic crop. The purity and authenticity of tea varieties are frequent problems in the conservation and promotion of germplasm resources in recent years, which has brought considerable inconvenience and uncertainty to the selection of parental lines for breeding and the research and cultivation of superior varieties. However, the development of core SNP markers can quickly and accurately identify the germplasm, which plays an important role in germplasm identification and the genetic relationship analysis of tea plants. In this study, based on 179,970 SNP loci from the whole genome of the tea plant, all of 142 cultivars were clearly divided into three groups: Assam type (CSA), Chinese type (CSS), and transitional type. Most CSA cultivars are from Yunnan Province, which confirms that Yunnan Province is the primary center of CSA origin and domestication. Most CSS cultivars are distributed in east China; therefore, we deduced that east China (mainly Zhejiang and Fujian provinces) is most likely the area of origin and domestication of CSS. Moreover, 45 core markers were screened using strict criteria to 179,970 SNP loci, and we analyzed 117 well-Known tea cultivars in China with 45 core SNP markers. The results were as follows: (1) In total, 117 tea cultivars were distinguished by eight markers, which were selected to construct the DNA fingerprint, and the remaining markers were used as standby markers for germplasm identification. (2) Ten pairs of parent and offspring relationships were confirmed or identified, and among them, seven pairs were well-established pedigree relationships; the other three pairs were newly identified. In this study, the east of China (mainly Zhejiang and Fujian provinces) is most likely the area of origin and domestication of CSS. The 45 core SNP markers were developed, which provide a scientific basis at the molecular level to identify the superior tea germplasm, undertake genetic relationship analysis, and benefit subsequent breeding work.

Progressive Genomic Approaches to Explore Drought- and Salt-Induced Oxidative Stress Responses in Plants under Changing Climate.

Drought and salinity are the major environmental abiotic stresses that negatively impact crop development and yield. To improve yields under abiotic stress conditions, drought- and salinity-tolerant crops are key to support world crop production and mitigate the demand of the growing world population. Nevertheless, plant responses to abiotic stresses are highly complex and controlled by networks of genetic and ecological factors that are the main targets of crop breeding programs. Several genomics strategies are employed to improve crop productivity under abiotic stress conditions, but traditional techniques are not sufficient to prevent stress-related losses in productivity. Within the last decade, modern genomics studies have advanced our capabilities of improving crop genetics, especially those traits relevant to abiotic stress management. This review provided updated and comprehensive knowledge concerning all possible combinations of advanced genomics tools and the gene regulatory network of reactive oxygen species homeostasis for the appropriate planning of future breeding programs, which will assist sustainable crop production under salinity and drought conditions.