Next generation crop improvement program: Progress and prospect in tea ( Camellia sinensis (L.) O. Kuntze)

Global transcriptome analysis reveals fungal disease responsive core gene regulatory landscape in tea

Fungal infections are the inevitable limiting factor for productivity of tea. Transcriptome reprogramming recruits multiple regulatory pathways during pathogen infection. A comprehensive meta-analysis was performed utilizing previously reported, well-replicated transcriptomic datasets from seven fungal diseases of tea. The study identified a cumulative set of 18,517 differentially expressed genes (DEGs) in tea, implicated in several functional clusters, including the MAPK signaling pathway, transcriptional regulation, and the biosynthesis of phenylpropanoids. Gene set enrichment analyses under each pathogen stress elucidated that DEGs were involved in ethylene metabolism, secondary metabolism, receptor kinase activity, and various reactive oxygen species detoxification enzyme activities. Expressional fold change of combined datasets highlighting 2258 meta-DEGs shared a common transcriptomic response upon fungal stress in tea. Pervasive duplication events caused biotic stress-responsive core DEGs to appear in multiple copies throughout the tea genome. The co-expression network of meta-DEGs in multiple modules demonstrated the coordination of appropriate pathways, most of which involved cell wall organization. The functional coordination was controlled by a number of hub genes and miRNAs, leading to pathogenic resistance or susceptibility. This first-of-its-kind meta-analysis of host-pathogen interaction generated consensus candidate loci as molecular signatures, which can be associated with future resistance breeding programs in tea.

Improvement of soil acidification in tea plantations by long-term use of organic fertilizers and its effect on tea yield and quality

Soil acidification in tea plantation seriously reduced the yield and quality of tea. It was an effective method to use organic fertilizer for acidified soil remediation to ensure tea yield and quality. In this study, different fertilizers were used to treat the acidified tea plantation soils for 4 consecutive years to analyze the remediation effect of different fertilizers on acidified soil and their effects on tea yield and quality. The results showed that during the period of 2017-2021, the soil pH value of tea plantation (S1) with long-term use of chemical fertilizer decreased continuously, from 3.07 to 2.82. In the tea plantation (S2), the soil pH value was stable between 4.26 and 4.65 in the combination of organic fertilizer and chemical fertilizer for a long time. The tea plantation (S3) with long-term use of organic fertilizer has a stable soil pH value between 5.13 and 5.33, which is most suitable for the growth of tea trees. The analysis results of tea yield and quality indicators (tea polyphenols, theanine, amino acids, caffeine, catechin components) showed that after long-term use of chemical fertilizer in S1 tea plantation, soil pH value decreased continuously, soil acidification intensified, tea tree growth was hindered, and tea yield and quality decreased continuously. S2 tea plantation used some organic fertilizer in combination with chemical fertilizer for a long time, the soil pH value gradually improved, soil acidification weakened, and tea yield and quality improved steadily. After long-term use of organic fertilizer in S3 tea plantation, soil acidification was significantly improved, which was conducive to the normal growth of tea trees and the yield and quality of tea reached the maximum. The results of interaction analysis showed that the long-term use of chemical fertilizer had a negative effect on the growth of tea trees, and the combination of organic fertilizer and chemical fertilizer improved the growth of tea trees to some extent, but the effect was poor, while the long-term use of organic fertilizer was the most beneficial to the growth of tea trees and most conducive to ensuring the yield and quality of tea. This study provides important practical significance for the remediation and fertilizer regulation of acidified tea plantation soils. In the process of field experiment, climate is a variable factor, and attention should be paid to the effect of climate change on fertilization efficiency in subsequent experiment.

Metabolic engineering in woody plants: challenges, advances, and opportunities

Woody plant species represent an invaluable reserve of biochemical diversity to which metabolic engineering can be applied to satisfy the need for commodity and specialty chemicals, pharmaceuticals, and renewable energy. Woody plants are particularly promising for this application due to their low input needs, high biomass, and immeasurable ecosystem services. However, existing challenges have hindered their widespread adoption in metabolic engineering efforts, such as long generation times, large and highly heterozygous genomes, and difficulties in transformation and regeneration. Recent advances in omics approaches, systems biology modeling, and plant transformation and regeneration methods provide effective approaches in overcoming these outstanding challenges. Promises brought by developments in this space are steadily opening the door to widespread metabolic engineering of woody plants to meet the global need for a wide range of sustainably sourced chemicals and materials.

Ecophysiological traits differentially modulate secondary metabolite accumulation and antioxidant properties of tea plant [Camellia sinensis (L.) O. Kuntze]

Owing to the diverse growing habitats, ecophysiology might have a regulatory impact on characteristic chemical components of tea plant. This study aimed to explore natural variations in the ecophysiological traits within seasons and the corresponding multifaceted biochemical responses given by the gene pool of 22 tea cultivars. Leaf temperature and intercellular carbon concentration (Ci), which varies as a function of transpiration and net photosynthesis respectively, have significant impact on the biochemical traits of the leaf. Occurrence of H₂O₂, in leaves, was associated to Ci that in turn influenced the lipid peroxidation. With the increment of Ci, total phenolics, epicatechin gallate (ECG), reducing power, and radical scavenging activity is lowered but total catechin and non-gallylated catechin derivatives (e.g. epicatechin or EC, epigallocatechin or EGC) are elevated. Leaf temperature is concomitantly associated (p ≤ 0.01) with phenolics, flavonoids, proanthocyanidin, tannin content, reducing power, iron chelation and free radical scavenging activities. Increased phenolic concentration in leaf cells, conceivably inhibit photosynthesis and moreover, gallic acid, thereafter conjugated to catechin derivatives. This study shed light on the fundamental information regarding ecophysiological impact on the quality determining biochemical characteristics of tea, which on further validation, might ascertain the genotype selection paradigm toward climate smart cultivation.

Genome-wide SNP discovery from Darjeeling tea cultivars - their functional impacts and application toward population structure and trait associations

Genotyping by sequencing and identification of functionally relevant nucleotide variations in crop accessions are the key steps to unravel genetic control of desirable traits. Elite cultivars of Darjeeling tea were undergone SNP genotyping by double-digest restriction-site associated DNA sequencing method. This study reports a set of 54,206 high-quality SNP markers discovered from ~10.4 GB sequence data, encompassing 15 chromosomes of the reference tea genome. Genetic relatedness among the accessions conforms to the analyses of Bayesian clustering, UPGMA, and PCoA methods. Genomic positions of the discovered SNPs and their putative effect on annotated genes designated a thoughtful understanding of their functional aspects in tea system biology. A group of 95 genes was identified to be affected by high impact variants. Genome-wide association analyses of 21 agronomic and biochemical phenotypes resulted in trait-linked polymorphic loci with strong confidence (p < 0.05 and 0.001).