A phased genome based on single sperm sequencing reveals crossover pattern and complex relatedness in tea plants

For diploid organisms that are highly heterozygous, a phased haploid genome can greatly aid in functional genomic, population genetic and breeding studies. Based on the genome sequencing of 135 single sperm cells of the elite tea cultivar ‘Fudingdabai’, we herein phased the genome of Camellia sinensis, one of the most popular beverage crops worldwide. High-resolution genetic and recombination maps of Fudingdabai were constructed, which revealed that crossover (CO) positions were frequently located in the 5′ and 3′ ends of annotated genes, while CO distributions across the genome were random. The low CO frequency in tea can be explained by strong CO interference, and CO simulation revealed the proportion of interference insensitive CO ranged from 5.2% to 11.7%. We furthermore developed a method to infer the relatedness between tea accessions and detected complex kinship and genetic signatures of 106 tea accessions. Among them, 59 accessions were closely related with Fudingdabai and 31 of them were first-degree relatives. We additionally identified genes displaying allele specific expression patterns between the two haplotypes of Fudingdabai and genes displaying significantly differential expression levels between Fudingdabai and other haplotypes. These results lay the foundation for further investigation of genetic and epigenetic factors underpinning the regulation of gene expression and provide insights into the evolution of tea plants as well as a valuable genetic resource for future breeding efforts.     

Electrotropism of pollen tubes of camellia and other plants

Summary Pollen tubes of Camellia japonica grew toward the cathode upon exposure to an electric field. Reversal of the field direction during the course of tube growth also reversed the direction of tube growth. These observations demonstrate the existence of the electrotropism of pollen tubes. This electro tropic response was confirmed in several kinds of pollen. The direction that the growing tube turned was found to differ with different pollen species, but it did not vary in those of the genus Camellia. The curvature in response to the electrotropic stimulus was influenced by calcium ion concentration as well as by the strength of the applied fields. The optimum condition for each was studied. The degree of tube extension decreased generally in inverse proportion to current density.     

The Polysaccharide Releasing Phenomenon and Cell Envelope of the Inositol-Exacting Yeast in Inositol-Deficiency

Inositol-deficiency abnormalized the cell envelope, wall and membrane, and the polysaccharides were released out of the cells in a greater amount in inositol-deficiency than in inositol-sufficiency. This release was most notable in the absence of inositol under the tested conditions. The released amount decreased when the culture was provided with inositol or phospholipids, or deprived of all growth-promoting vitamins. Gel filtration of released polysaccharides showed that the lower molecular fraction increased in inositol-deficiency than in sufficiency. DEAE-Sephadex chromatography of released polysaccharides showed the presence of fractions specific for inositol-deficiency which contained mannan and phosphates. Inositol-deficiency also caused enlarging of the pore size of the cell-wall. The relationship between the release of polysaccharides and the syntheses of cell-wall polysaccharides was investigated and discussed.     

金花茶花瓣转录组分析及花瓣发育调控基因挖掘

花瓣大小是影响金花茶(Camellia nitidissima)观赏价值的主要因素之一,但金花茶花瓣发育形成机制尚不清楚。将金花茶花瓣发育过程划分为幼蕾期(S1)、初蕾期(S2)、显色期(S3)、半开期(S4)、盛开期(S5)五个阶段,利用RNA-seq技术分析花发育过程中转录组的动态变化,以期对金花茶花瓣发育形成的转录机理进行初步探究。通过对金花茶花瓣发育过程中的差异表达基因进行富集分析和趋势分析,发现生长素转导途径所含差异表达基因数量最多,部分AUX1/LAX共转运体、AUX/IAA基因、SAUR等生长素应答基因在开花过程中明显上调,表明生长素是调控花瓣生长重要的调控因子。MYB、bHLH、锌指蛋白等转录因子、木葡聚糖内糖基转移酶/水解酶(XTH)、果胶酯酶(PE)、果胶裂解酶(PL)等部分下游功能基因,其中XTH显著富集于GO分类中的水解酶活性,表明它们可能对金花茶花瓣的生长起重要调控作用。此外,对FT、SOC1、AP3、PI、SEP3等开花调控关键基因在金花茶花瓣发育过程中的表达情况进行了分析,结果表明这些基因主要以中低表达为主。高表达基因进行KEGG富集分析结果表明,次生代谢物质合成伴随着金花茶花瓣的整个发育过程。这些结果为进一步揭示金花茶花瓣发育的转录调控机制奠定了理论基础。