Fluorescence visualization of cellulose and pectin in the primary plant cell wall.

Plant cell walls constitute the extracellular matrix surrounding plant cells and are composed mainly of polysaccharides. The chemical makeup of the primary plant cell wall, and specifically, the abundance, localization and arrangement of the constituting polysaccharides are intimately linked with growth, morphogenesis and differentiation in plant cells. Visualization of the cell wall components is, therefore, a crucial tool in plant cell developmental studies. In this technical update, we present protocols for fluorescence visualization of cellulose and pectin in selected plant tissues and illustrate examples of some of the available labels that hold promise for live imaging of plant cell wall expansion and morphogenesis.

In-depth Understanding of Camellia oleifera Self-incompatibility by Comparative Transcriptome, Proteome and Metabolome.

Oil-tea tree (Camellia oleifera) is the most important edible oil tree species in China with late-acting self-incompatibility (LSI) properties. The mechanism of LSI is uncertain, which seriously hinders the research on its genetic characteristics, construction of genetic map, selection of cross breeding parents and cultivar arrangement. To gain insights into the LSI mechanism, we performed cytological, transcriptomic, proteomic and metabolomic studies on self- and cross-pollinated pistils. The studies identified 166,591 transcripts, 6851 proteins and 6455 metabolites. Transcriptomic analysis revealed 1197 differentially expressed transcripts between self- and cross-pollinated pistils and 47 programmed cell death (PCD)-control transcripts. Trend analysis by Pearson correlation categorized nine trend graphs linked to 226 differentially expressed proteins and 38 differentially expressed metabolites. Functional enrichment analysis revealed that the LSI was closely associated with PCD-related genes, mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signal transduction, ATP-binding cassette (ABC) transporters and ubiquitin-mediated proteolysis. These particular trends in transcripts, proteins and metabolites suggested the involvement of PCD in LSI. The results provide a solid genetic foundation for elucidating the regulatory network of PCD-mediated self-incompatibility in C. oleifera.

A cytological study of anther and pollen development in Camellia oleifera.

The plant species Camellia oleifera is an important producer of edible oil in China. However, it suffers from a low fruit-setting rate. This study used high resolution scanning electron microscopy of semi-thin tissue sections to investigate anther development and pollen formation, and to determine whether problems in forming functional pollen cause low seed setting rates. During anther development, cell sizes within the epidermis and end othecium gradually increase, and at the beginning of the microsporocyte phase, the cells become highly vacuolated. The cell walls of the inner wall cells thicken in a ribbon pattern during the later part of the two-cell pollen stage. Middle layer cells become flattened during the later part of the secondary sporogenous cell stage. A tapetum also forms at this stage; the secondary sporogenous cells begin to degrade at the early microspore stage and completely disappear by the time the pollen is mature, thus forming a glandular tapetum. In microsporocyte, cytokinesis occurs simultaneously with microsporocyte meiosis, and a tetrahedral arrangement is present in tetrads. Reproductive cells begin to form at the later stage of microsporogenesis; the nuclei of the reproductive cells are enlarged as the reproductive cells begin to move away from the pollen wall. Two-cell pollen is first formed after reproductive cells have left the pollen wall, and the number of inclusions in the pollen subsequently increases. The pollen matures for 5-8 days before flowering occurs. No pollen abortion phenomena were observed, suggesting that anther development in C. oleifera is normal and that functional pollen are formed.

Thirteen Camellia chloroplast genome sequences determined by high-throughput sequencing: genome structure and phylogenetic relationships.

BACKGROUND: Camellia is an economically and phylogenetically important genus in the family Theaceae. Owing to numerous hybridization and polyploidization, it is taxonomically and phylogenetically ranked as one of the most challengingly difficult taxa in plants. Sequence comparisons of chloroplast (cp) genomes are of great interest to provide a robust evidence for taxonomic studies, species identification and understanding mechanisms that underlie the evolution of the Camellia species. RESULTS: The eight complete cp genomes and five draft cp genome sequences of Camellia species were determined using Illumina sequencing technology via a combined strategy of de novo and reference-guided assembly. The Camellia cp genomes exhibited typical circular structure that was rather conserved in genomic structure and the synteny of gene order. Differences of repeat sequences, simple sequence repeats, indels and substitutions were further examined among five complete cp genomes, representing a wide phylogenetic diversity in the genus. A total of fifteen molecular markers were identified with more than 1.5% sequence divergence that may be useful for further phylogenetic analysis and species identification of Camellia. Our results showed that, rather than functional constrains, it is the regional constraints that strongly affect sequence evolution of the cp genomes. In a substantial improvement over prior studies, evolutionary relationships of the section Thea were determined on basis of phylogenomic analyses of cp genome sequences. CONCLUSIONS: Despite a high degree of conservation between the Camellia cp genomes, sequence variation among species could still be detected, representing a wide phylogenetic diversity in the genus. Furthermore, phylogenomic analysis was conducted using 18 complete cp genomes and 5 draft cp genome sequences of Camellia species. Our results support Chang's taxonomical treatment that C. pubicosta may be classified into sect. Thea, and indicate that taxonomical value of the number of ovaries should be reconsidered when classifying the Camellia species. The availability of these cp genomes provides valuable genetic information for accurately identifying species, clarifying taxonomy and reconstructing the phylogeny of the genus Camellia.

In vitro study of oscillatory growth dynamics of Camellia pollen tubes in microfluidic environment.

A hallmark of tip-growing cells such as pollen tubes and fungal hyphae is their oscillatory growth dynamics. The multiple aspects of this behavior have been studied to identify the regulatory mechanisms that drive the growth in walled cells. However, the limited temporal and spatial resolution of data acquisition has hitherto prevented more detailed analysis of this growth behavior. To meet this challenge, we employed a microfluidic device that is able to trap pollen grains and to direct the growth of pollen tubes along microchannels filled with liquid growth medium. This enabled us to observe the growth behavior of Camellia pollen tubes without the use of the stabilizer agarose and without risking displacement of the cell during time lapse imaging. Using an acquisition interval of 0.5 s, we demonstrate the existence of primary and secondary peak frequencies in the growth dynamics. The effect of sucrose concentration on the growth dynamics was studied through the shift in these peak frequencies indicating the pollen tube's ability to modulate its growth activity.