The tung tree (Vernicia fordii) is one of only a few plant species that produces high oil-yielding seeds rich in α-eleostearic acid (α-ESA, 18:3Δ9cis, 11trans, 13trans), a conjugated trienoic fatty acid with valuable industrial and medical properties. Previous attempts have been made to engineer tung oil biosynthesis in transgenic oilseed crops, but these efforts have met with limited success. Here we present a high-quality genome assembly and developing seed transcriptomic data set for this species. Whole-genome shotgun sequencing generated 176 Gb of genome sequence data used to create a final assembled sequence 1,176,320 kb in size, with a scaffold N50 size of >474 kb, and containing approximately 47,000 protein-coding genes. Genomic and transcriptomic data revealed full-length candidate genes for most of the known and suspected reactions that are necessary for fatty acid desaturation/conjugation, acyl editing and triacylglycerol biosynthesis. Seed transcriptomic analyses also revealed features unique to tung tree, including unusual transcriptional profiles of fatty acid biosynthetic genes, and co-ordinated (and seemingly paradoxical) simultaneous up-regulation of both fatty acid β-oxidation and triacylglycerol biosynthesis in mid-development seeds. The precise temporal control of the expression patterns for these two pathways may account for α-ESA enrichment in tung seeds, while controlling the levels of potentially toxic by-products. Deeper understanding of these processes may open doors to the design of engineered oilseeds containing high levels of α-ESA.
Tea-oil tree (Camellia oleifera Abel) is an important edible oil woody plant with a planting area over 3,800,000 hectares in southern China. Anthracnose is a serious disease of tea-oil tree in southern China, causing severe economic losses and posing a huge threat to the Ca. oleifera industry. Based on recent developments in the classification of Colletotrichum species, the objective of this study was to identify Colletotrichum species associated with tea-oil tree and examine their pathogenicity on leaves and fruits of Ca. oleifera. In total, 232 isolates were obtained from Ca. oleifera leaves and fruits with anthracnose symptoms. These isolates were further characterized based on morphology and multilocus phylogenetic analyses using partial DNA sequences at the ribosomal internal transcribed spacer regions and β-tubulin, actin, calmodulin, glyceraldehyde-3-phosphate dehydrogenase, and chitin synthase-encoding genes. The fungal isolates belong to five species: C. camelliae, C. fructicola, C. siamense, C. aenigma, and C. gloeosporioides. C. camelliae was the most predominant and widely distributed species on fruits of Ca. oleifera (91.4%), followed by C. fructicola (6.3%). However, C. fructicola was common and widely distributed species on leaves (75.9%), followed by C. camelliae (17.2%). There was no evidence of geographical specialization of the different species. Pathogenicity assays showed that all tested isolates, including 20 of C. camelliae, 11 of C. fructicola, four of C. siamense, two of C. aenigma, and one of C. gloeosporioides, were pathogenic to leaves and fruits of Ca. oleifera. Among the five species, C. camelliae species showed strong pathogenicity on both leaves and fruits of Ca. oleifera, and C. fructicola, C. siamense, C. aenigma, and C. gloeosporioides all showed weak pathogenicity on both leaves and fruits. No relationship was found between origin of isolates and their virulence. This is the first description of C. camelliae, C. fructicola, C. siamense, and C. gloeosporioides from the fruits of Ca. oleifera in China.
To assess the adaptability of Camellia oleifera for introduction in new growth locations, this study evaluated 10 representative C. oleifera cultivars from the main areas in China where this oil-producing evergreen crop is grown. Cluster analysis, correlation analysis, and membership function analysis were used to evaluate various indices of the selected C. oleifera cultivars, including flowering phenology, cold tolerance, leaf structure, pollen characteristics, and pollen viability. The correlation analysis identified the full blossoming time, leaf palisade and spongy tissue thickness, pollen deformity rate, and pollen activity as key indices for determining the adaptability of the cultivars to new areas. The membership function analysis of the 10 C. oleifera cultivars revealed the following order of adaptability: ‘XLC25’ > ‘Changlin4hao’ > ‘Ganzhouyou8hao’ > ‘Ganzhouyou6hao’ > ‘Tiechengyihao’ > ‘Eyou465’ > ‘XLC10’ > ‘Changlin3hao’ > ‘Changlin18hao’ > ‘QY235.’ When introducing C. oleifera cultivars to new regions, the higher-ranked cultivars are more likely to be successful. The results of this study may provide a new direction for the comprehensive assessment of plant introduction and domestication potential, i.e., the assessment of the vegetative and reproductive growth, adversity resistance, and blossoming time of plants.
Camellia oleifera is one of the four woody oil plants in the world, which is widely cultivated in South China. To examine the genetic diversity of C. oleifera in China, the diversity and genetic relationships among and within major populations of 109 varieties of C. oleifera were analyzed using ISSR markers. Twenty-three ISSR primers out of 49 primers yielded approximately 487 legible bands. A total of 335 of these bands were polymorphic markers, and the ratio of polymorphism was 68.86%. From the results, Zhejiang province showed the highest populations genetic diversity (H value 0.18), while Guangxi population showed the lowest genetic diversity (H 0.0851). Base on the bands, the genetic similarity coefficient ranged from 0.61 to 0.93 using NTSYS2.10e software. When coefficient was 0.75, 109 cultivars were divided into 11 categories and categories I contain 79 varieties by UPGMA cluster analysis. The test varieties divided into 7 sub-groups when categories were 0.75, which show a close genetic relationship. Results advised that Hunan is the main producing area of C. oleifera, with enriched C. oleifera variety and complex topography, and therefore has a high genetic diversity. Meanwhile, the main varieties of C. oleifera in Hubei are imported from Hunan, which results in fewer varieties and reduces the genetic diversity of C. oleifera. The ISSR profiles can improve C. oleifera germplasm management and provide potential determine correlations between different varieties and its distribution in different province.
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