The section Oleifera (Theaceae) has attracted attention for the high levels of unsaturated fatty acids found in its seeds. Here, we report the chromosome-scale genome of the sect. Oleifera using diploid wild Camellia lanceoleosa with a final size of 3.00 Gb and an N50 scaffold size of 186.43 Mb. Repetitive sequences accounted for 80.63% and were distributed unevenly across the genome. Camellia lanceoleosa underwent a whole-genome duplication event approximately 65 million years ago (65 Mya), prior to the divergence of C. lanceoleosa and Camellia sinensis (approx. 6-7 Mya). Syntenic comparisons of these two species elucidated the genomic rearrangement, appearing to be driven in part by the activity of transposable elements. The expanded and positively selected genes in C. lanceoleosa were significantly enriched in oil biosynthesis, and the expansion of homomeric acetyl-coenzyme A carboxylase (ACCase) genes and the seed-biased expression of genes encoding heteromeric ACCase, diacylglycerol acyltransferase, glyceraldehyde-3phosphate dehydrogenase and stearoyl-ACP desaturase could be of primary importance for the high oil and oleic acid content found in C. lanceoleosa. Theanine and catechins were present in the leaves of C. lanceoleosa. However, caffeine can not be dectected in the leaves but was abundant in the seeds and roots. The functional and transcriptional divergence of genes encoding SAM-dependent N-methyltransferases may be associated with caffeine accumulation and distribution. Gene expression profiles, structural composition and chromosomal location suggest that the late-acting self-incompatibility of C. lanceoleosa is likely to have favoured a novel mechanism co-occurring with gametophytic self-incompatibility. This study provides valuable resources for quantitative and qualitative improvements and genome assembly of polyploid plants in sect. Oleifera.
Camellia oil extracted from the seeds of Camellia oleifera Abel. is a popular and high-quality edible oil, but its yield is limited by seed setting, which is mainly caused by self-incompatibility (SI). One of the obvious biological features of SI plants is the inhibition of self-pollen tubes; however, the underlying mechanism of this inhibition in C. oleifera is poorly understood. In this study, we constructed a semi-in vivo pollen tube growth test (SIV-PGT) system that can screen for substances that inhibit self-pollen tubes without interference from the genetic background. Combined with multi-omics analysis, the results revealed the important role of galloylated catechins in self-pollen tube inhibition, and a possible molecular regulatory network mediated by UDP-glycosyltransferase (UGT) and serine carboxypeptidase-like (SCPL) was proposed. In summary, galloylation of catechins and high levels of galloylated catechins are specifically involved in pollen tube inhibition under self-pollination rather than cross-pollination, which provides a new understanding of SI in C. oleifera. These results will contribute to sexual reproduction research on C. oleifera and provide theoretical support for improving Camellia oil yield in production.
The importance of a data exchanging culture accompanied by a supporting bioinformatic system is widely praised as an aid to sustainable development. Yet this is not always implemented as a top-down procedure in every governing environment. Common obstacles include lack of resources, lack of support from decision-makers, and lack of recognition from data-providers. Using citizen science (hereafter CS), which assumes a spirit of public information sharing, we demonstrate how CS can be a critical tool to help database managers overcome this difficulty. CS data contributes to impressively over 70% of the currently 4.5 million openly distributed occurrence data in Taiwan. Although CS projects emerged much earlier in a few taxa, such as Aves and Anura, CS was unknown to the wider public and politicians in the region until 2009. This was probably due to the combination of the popularity of social media and improvements to wifi connections, which brought discoveries and impacts of CS data to the news spotlight. Such cases include roadkill projects that aided rabies-outbreak control, and amateur bird records that helped downscale the conflict between solar energy deployment and migratory wetland bird conservation. These cases also created feedback on the call for more data to be open, an effect that was prominent from project managers in other CS communities, the previously reluctant expert researcher communities, and even placed pressure on data policy of several conservation agencies which previously were not supportive of open data. The inclusion of CS programs is also critical in forming alliances between agencies that were responsible for promoting and building the biodiversity informatics system. Previously, financial and human resources for such systems are split across agencies. However, in terms of building up a cutting edge biodiversity information service platform, or empowerment of human resources to handle the rapidly growing amount of data, joint partnerships across government agencies is then necessary. CS brings the spotlight of government efforts to the people, which is an important strategy to maintain support from top decision-makers and politicians, who mostly rely on public votes in a democratic society. Currently, the national node of the Global Biodiversity Information Facility in Taiwan, the administration for conservation in Taiwan, and the main biodiversity consultancy in Taiwan have teamed up, answering the call for sharing data for a better future. As a tribute to the CS projects, a biodiversity informatics system named Taiwan Biodiversity Network, is now enhancing its ability as a platform to promote data usage and provide technical aid to CS programs. Data visualization projects such as “Coldspots” pointed out regions that lack data, which can be used to decide where to focus efforts for the next field surveys. Online CS data platforms, such as Taiwan Reptile Report Program, are also working to ease the previously intensive efforts that project managers needed to contribute to run event-based monitoring. Combined, these developments form a cultural and technical basis for the implementation of multi-taxa atlas projects, which was made possible by the mainstreaming of open data culture and biodiversity awareness through citizen science projects.
Camellia yuhsienensis was used to cross with Camellia oleifera to improve the resistance of oil camellia anthracnose. However, unilateral cross-incompatibility (UCI) between C. oleifera and C. yuhsienensis was found during the breeding process. Five C.oleifera cultivars and four C. uhsienensis materials were tested to confirm the UCI between C. oleifera and C. yuhsienensis. ‘Huashuo’ (HS) and ‘Youza 2’ (YZ2) were used to represent these two species to characterize the UCI, including pollen tube growth, fertilization and fruit development. The results demonstrated that UCI was prevalent between C. oleifera and C. yuhsienensis. The asynchronous flowering period was a pre-pollination barrier that limited mating between these two species under natural conditions. Interspecific pollen tubes were observed through the styles of these two plants, though the growth rates differed considerably. At 96 hours after pollination, the pollen tube of YZ2 barely entered the ovule, but remained at the base of the style and became swollen. However, the HS pollen tube entered the ovule 48 hours after pollination, double fertilization was observed, and the fruit and seeds developed commonly. Relative to compatible combinations, most unfertilized ovules in incompatible combinations failed to grow, turned brown 150 days after pollination, and the fruits were smaller than expected with uneven enlargement. Investigations on both semi-in vivo and in vitro pollen tubes gave us new idea for thought: the HS style has a stronger inhibitory effect on the interspecific pollen tubes, while calcium alleviates the inhibitory of styles but failed to prevent the appearance of abnormal pollen tube morphology. This study provides useful information on interspecific hybridization between C. oleifera and C. yuhsienensis for understanding reproductive isolation mechanisms and breeding programs in genus Camellia.
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