Flowering Research in Taiwan

Abstract

Flowering is an important and highly regulated process. Taiwanese researchers have contributed significantly to understanding flowering biology, including cell biology, cytogenetics and functional genomics, in rice, lily and especially orchids. In recognition of this effort, the PCP Editorial Board is publishing a special issue on flowering research in Taiwan. This issue contains seven articles on cutting-edge topics or reviews of flowering research carried out in Taiwan, focusing on research into orchids and lily. An anther consists of sporophytic tissues of three outer cell layers and an innermost layer, the tapetum. The tapetum has attracted the most attention. Tapetum cells are important in nurturing the maturing microspores, and their ablation leads to microspore death and thus male sterility (Hesse et al. 1993). In a review paper, M.-D. Huang et al. (pp. 1459–1466) provide information about current studies on the transcriptome of the anther sporophyte, including microarray and next-generation sequencing data. The authors illustrate a proposed gene regulation network of anther development in Arabidopsis using the most updated references. In addition, they point out potential studies worthwhile pursuing, including those of ‘secretomes’, antisense transcripts and small RNAs. Finally, they propose a model for exine precursor biosynthesis in tapetum cells and transport of these precursors from the tapetum cell to the microspore surface. With an estimated >25,000 species, orchids are the most species-rich of all angiosperm families (Leitch et al. 2009). They show a wide diversity of epiphytic and terrestrial growth forms and have successfully colonized almost every habitat on earth. The expansion of the orchid family probably took place in a comparatively short period as compared with that of most flowering plant families, which suggests exceptionally high speciation rates (Gill 1989). The production of orchids in the world has increased 12–18% every year since 2000. Taiwan is one of the world-renowned countries exporting orchids, because the climate is congenial to the growth of orchids and because of the rich resource of native species and advances in breeding techniques to produce more beautiful and elegant new varieties. Taiwan’s orchid industry has been recognized by the international community as prosperous in terms of sales volume, orchid plantation, orchid-growing technologies and financial resources. The most popular potted flowering plants are Phalaenopsis hybrids, and Oncidium are the top-traded cut flowers. Most, if not all, orchid flowers on the market are hybrids, such as Phalaenopsis spp., although most researchers use inbred lines such as Phalaenopsis equestris as materials for detailed studies. Fig. 1 illustrates several examples of orchid varieties, their mutants, disease and insect infection, as well as orchid production. In the second review paper of this issue, Hsiao et al. (pp. 1467–1486) provide an overview of the research activities in orchid biology and biotechnology, including the status of genomics, transformation technology, flowering regulation, molecular regulatory mechanisms of floral development, scent production and color presentation. The authors also point out the pros and cons of using orchids for genome research. Oncidium is a valuable floral genus of orchid. The yellow color is most often seen in the flower market. The largest flower structure is the labellum, also known as the lip (fig. 1E, p. 1533). Chang et al. (pp. 1532–1545) used 454 sequencing to perform deep sequencing of the Oncidium transcriptome using six organs. A value-added expressed sequence tag (EST) database, OncidiumOrchidGenomeBase (http://predictor.nchu. edu.tw/oogb/), was constructed and provides a foundation for molecular genetics and functional genomics for modifying the flowering quality and desirable agronomic traits of Oncidium. The authors also identified flowering time-associated genes, including photoreceptors and floral pathway integrators. Su et al. (pp. 1501–1514) performed transcriptome analysis of mixed vegetative and reproductive tissues of the moth orchid Phalaenopsis aphrodite and constructed the Orchidstra genome database (http://orchidstra.abrc.sinica.edu.tw) for searching and linking to corresponding Pfam, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Fu et al. (2011) prepared an EST database from 11 tissues collected from three orchid species, i.e. P. equestris, P. aphrodite and P. bellina, using both traditional and next-generation sequencing. This OrchidBase is freely available at http://lab.fhes.tn.edu.tw/est. Altogether, these three transcriptome databases consist of about 100,000 contigs from four orchid species and thus provide tremendous resources for orchid functional genomics studies as well as breeding application. Although the floral ABCDE model is generally thought to be ubiquitous in the core eudicots, studies of basal angiosperms,