LUX ARRHYTHMO links CBF pathway and jasmonic acid metabolism to regulate cold tolerance of tea plants.

Cold stress declines the quality and yield of tea, yet the molecular basis underlying cold tolerance of tea plants (Camellia sinensis) remains largely unknown. Here, we identified a circadian rhythm component LUX ARRHYTHMO (LUX) that potentially regulates cold tolerance of tea plants through a genome-wide association study and transcriptomic analysis. The expression of CsLUX phased with sunrise and sunset and was strongly induced by cold stress. Genetic assays indicated that CsLUX is a positive regulator of freezing tolerance in tea plants. CsLUX was directly activated by CsCBF1 and repressed the expression level of CsLOX2, which regulates the cold tolerance of tea plants through dynamically modulating jasmonic acid content. Furthermore, we showed that the CsLUX-CsJAZ1 complex attenuated the physical interaction of CsJAZ1 with CsICE1, liberating CsICE1 with transcriptional activities to withstand cold stress. Notably, a single-nucleotide variation of C-to-A in the coding region of CsLUX was functionally validated as the potential elite haplotype for cold response, which provided valuable molecular markers for future cold resistance breeding in tea plants.

Agrobacterium Transformation of Tea Plants (Camellia sinensis (L.) KUNTZE): A Small Experiment with Great Prospects.

Tea has historically been one of the most popular beverages, and it is currently an economically significant crop cultivated in over 50 countries. The Northwestern Caucasus is one of the northernmost regions for industrial tea cultivation worldwide. The domestication of the tea plant in this region took approximately 150 years, during which plantations spreading from the Ozurgeti region in northern Georgia to the southern city of Maykop in Russia. Consequently, tea plantations in the Northern Caucasus can serve as a source of unique genotypes with exceptional cold tolerance. Tea plants are known to be recalcitrant to Agrobacterium-mediated transfection. Research into optimal transfection and regeneration methodologies, as well as the identification of tea varieties with enhanced transformation efficiency, is an advanced strategy for improving tea plant culture. The aim of this study was to search for the optimal Agrobacterium tumefaciens-mediated transfection protocol for the Kolkhida tea variety. As a result of optimizing the transfection medium with potassium phosphate buffer at the stages of pre-inoculation, inoculation and co-cultivation, the restoration of normal morphology and improvement in the attachment of Agrobacterium cells to the surface of tea explants were observed by scanning electron microscopy. And an effective method of high-efficiency Agrobacteria tumefaciens-mediated transfection of the best local tea cultivar, Kolkhida, was demonstrated for the first time.

Recent progress and perspectives on physiological and molecular mechanisms underlying cold tolerance of tea plants.

Tea is one of the most consumed and widely planted beverage plant worldwide, which contains many important economic, healthy, and cultural values. Low temperature inflicts serious damage to tea yields and quality. To cope with cold stress, tea plants have evolved a cascade of physiological and molecular mechanisms to rescue the metabolic disorders in plant cells caused by the cold stress; this includes physiological, biochemical changes and molecular regulation of genes and associated pathways. Understanding the physiological and molecular mechanisms underlying how tea plants perceive and respond to cold stress is of great significance to breed new varieties with improved quality and stress resistance. In this review, we summarized the putative cold signal sensors and molecular regulation of the CBF cascade pathway in cold acclimation. We also broadly reviewed the functions and potential regulation networks of 128 cold-responsive gene families of tea plants reported in the literature, including those particularly regulated by light, phytohormone, and glycometabolism. We discussed exogenous treatments, including ABA, MeJA, melatonin, GABA, spermidine and airborne nerolidol that have been reported as effective ways to improve cold resistance in tea plants. We also present perspectives and possible challenges for functional genomic studies on cold tolerance of tea plants in the future.

Population Analysis of Diospyros lotus in the Northwestern Caucasus Based on Leaf Morphology and Multilocus DNA Markers.

Diospyros lotus is the one of the most frost-tolerant species in the Diospyros genera, used as a rootstock for colder regions. Natural populations of D. lotus have a fragmented character of distribution in the Northwestern Caucasus, one of the coldest regions of Diospyros cultivation. To predict the behavior of D. lotus populations in an extreme environment, it is necessary to investigate the intraspecific genetic diversity and phenotypic variability of populations in the colder regions. In this study, we analyzed five geographically distant populations of D. lotus according to 33 morphological leaf traits, and the most informative traits were established, namely, leaf length, leaf width, leaf index (leaf to length ratio) and the length of the fourth veins. Additionally, we evaluated the intraspecific genetic diversity of D. lotus using ISSR and SCoT markers and proposed a new parameter for the evaluation of genetic polymorphism among populations, in order to eliminate the effect of sample number. This new parameter is the relative genetic polymorphism, which is the ratio of polymorphism to the number of samples. Based on morphological and genetic data, the northernmost population from Shkhafit was phenotypically and genetically distant from the other populations. The correspondence between several morphological traits (leaf width, leaf length and first to fifth right vein angles) and several marker bands (SCoT5, SCoT7, SCoT30: 800-1500 bp; ISSR13, ISSR14, ISSR880: 500-1000 bp) were observed for the Shkhafit population. Unique SCoT and ISSR fragments can be used as markers for breeding purposes. The results provide a better understanding of adaptive mechanisms in D. lotus in extreme environments and will be important for the further expansion of the cultivation area for persimmon in colder regions.

Transferability of ISSR, SCoT and SSR Markers for Chrysanthemum × Morifolium Ramat and Genetic Relationships Among Commercial Russian Cultivars.

Characterization of genetic diversity in germplasm collections requires an efficient set of molecular markers. We assessed the efficiency of 36 new SCoT markers, 10 new ISSR markers, and 5 microsatellites for the characterization of genetic diversity in chrysanthemum core collection of 95 accessions (Russian and foreign cultivars). Seven new SCoT (SCoT12, 20, 21, 23, 29, 31, 34) and six new ISSR markers ((GA)8T, (CT)8G, (CTTCA)3, (GGAGA)3, (TC)8C, (CT)8TG) were efficient for the genetic diversity analysis in Chrysanthemum × morifolium collection. After STRUCTURE analysis, most Russian cultivars showed 20-50% of genetic admixtures of the foreign cultivars. Neighbor joining analysis based on the combination of SSR, ISSR, and SCoT data showed the best accordance with phenotype and origin compared to the separate analysis by each marker type. The position of the accessions within the phylogenetic tree corresponded with the origin and with some important traits, namely, plant height, stem and peduncle thickness, inflorescence type, composite flower and floret types, flower color, and disc color. In addition, several SCoT markers were suitable to separate the groups distinctly by the phenotypical traits such as plant height (SCoT29, SCoT34), thickness of the stem and peduncle (SCoT31, SCoT34), and leaf size and the floret type (SCoT31). These results provide new findings for the selection of markers associated with important traits in Chrysanthemum for trait-oriented breeding and germplasm characterization.

Genetic Diversity in Diospyros Germplasm in the Western Caucasus Based on SSR and ISSR Polymorphism.

Persimmon germplasm in the Western Caucasus represent one of the most northerly collections. In our study, 51 commercial cultivars of D. kaki, 3 accessions of D. virginiana and 57 D. lotus accessions from six geographically distant populations were investigated using 19 microsatellite and 10 inter simple sequence repeat (ISSR) markers. After STRUCTURE analysis, the single accessions of Diospyros were allocated to three genetic clusters. Genetic admixtures in the important genotypes of D. kaki were revealed, whereas D. lotus accessions showed no admixture with other genetic clusters. The correspondence of genetic data and phenotypical traits was estimated in the D. kaki collection. The most frost tolerant genotypes of the collection, such as "Mountain Rogers", "Nikitskaya Bordovaya", "Rossiyanka", "MVG Omarova", "Meader", "Costata", "BBG", and "Jiro", showed a high percentage of genetic admixtures and were grouped close to D. virginiana. Some of these genotypes are known to be interspecific hybrids with D. virginiana. A low level of genetic diversity between the distant D. lotus populations was revealed and it can be speculated that D. lotus was introduced to the Western Caucasus from a single germplasm source. These results are an important basis for the implementation of conservation measures, developing breeding strategies, and improving breeding efficiency.

Characterization of genome-wide genetic variations between two varieties of tea plant (Camellia sinensis) and development of InDel markers for genetic research.

BACKGROUND: Single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) are the major genetic variations and are distributed extensively across the whole plant genome. However, few studies of these variations have been conducted in the long-lived perennial tea plant. RESULTS: In this study, we investigated the genome-wide genetic variations between Camellia sinensis var. sinensis 'Shuchazao' and Camellia sinensis var. assamica 'Yunkang 10', identified 7,511,731 SNPs and 255,218 InDels based on their whole genome sequences, and we subsequently analyzed their distinct types and distribution patterns. A total of 48 InDel markers that yielded polymorphic and unambiguous fragments were developed when screening six tea cultivars. These markers were further deployed on 46 tea cultivars for transferability and genetic diversity analysis, exhibiting information with an average 4.02 of the number of alleles (Na) and 0.457 of polymorphism information content (PIC). The dendrogram showed that the phylogenetic relationships among these tea cultivars are highly consistent with their genetic backgrounds or original places. Interestingly, we observed that the catechin/caffeine contents between 'Shuchazao' and 'Yunkang 10' were significantly different, and a large number of SNPs/InDels were identified within catechin/caffeine biosynthesis-related genes. CONCLUSION: The identified genome-wide genetic variations and newly-developed InDel markers will provide a valuable resource for tea plant genetic and genomic studies, especially the SNPs/InDels within catechin/caffeine biosynthesis-related genes, which may serve as pivotal candidates for elucidating the molecular mechanism governing catechin/caffeine biosynthesis.