| Potato(Solarium tuberosum L.), a member of the Solanaceae, ranks the fourth most important food crop after rice, wheat, and maize (http://www.fao.org/)., and plays a crucial role in global food security. Potato tubers—the modified underground stems that are rich in starch, protein, antioxidants and vitamins—are the most important organ of the species. Tuber formation has thus attracted considerable attention, with a view to improve yields and provide a model system to look into the development of modified organs in plants. Potato tuberization is influenced by light quality and photoperiod. Effects of light quality on potato tuber formation in vitro is not well studied. Photoperiodic regulation of potato tuber formation is a very complex biological process that requires the interaction of diverse genes and the crosstalk of several pathways. Photoperiodic control of potato tuber formation is far from been fully elucidated. New genomics tools, especially high-throughput sequencing, should considerably facilitate the identification of candidate genes involved in the photoperiodic control of tuber formation in potato.The main purposes of present research are to investigate the effects of light quality on potato tuberization in vitro for efficient selection of light source for microtuber production, and to identify candidate genes involved in the photoperiodic tuberization approaching insight the mechanism of photoperiodic regulation of potato tuberization. The main results obtained are as below.1) By treating8potato genotyes with white, red and blue light in vitro, number of microtuber formed per plantlet and mean weight of the microtubers were investigated. The data showed that light quality for plant growth (LP), light quality for microtuberinitiation and growth (LM) and potato genotype impacted tuber formation dramatically. Generally, white light promoted microtuber formation while red light repressed the tuberization. Blue light was more suitable for tuber growth after tuber initiation.2) Phenotypic characterization of E26, E20and E109, the three sister lines derived from same cross, indicated thattuberization of E26is photoperiod-sensitive characterized by tuber formation only occurs at short day (8h/d). E109is phtoperiod-independent for tuberization since it can form tubers at either short day or long day (16h/d), whereas E20is not capable to produce tubers at either of the daylength which is also considered photoperiod-independent. These three clones are desirable for research on the photoperiodic regulation of potato tuberization in present research.3) Digital Gene Expression (DGE) Tag Profiling analysis of the short-day-sensitive clone E26identified2,218genes that were differentially regulated by day length.4) Gene ontology (GO) and KEGG pathway analyses of DEGs found that DEGs involved117pathways and21biological processes. These results indicated that the response of potato to photoperiod requires the interaction of diverse genes and the crosstalk of several pathways.5) According to GO and KEGG pathway annotation, we selected56genes associated with circadian rhythmicity, signal transduction, and development. Quantitative transcriptional analysis in the selected clones revealed five genes potentially associated with photoperiodic tuberization, which were predicted to encode a DOF protein (PGSC0003DMT400083080), a blue light receptor (PGSC0003DMT400068851), a lectin (PGSC0003DMT400034146), a syntaxin-like protein (PGSC0003DMT400043211), and a protein with unknown function (PGSC0003DMT400022042).Our research provide a theoretical base for light source selection in microtuber production. Identification of the key candidate genes involved in photoperiodic-regulated tuberization gains insight the novel gene resources for further dissecting photoperiodic regulation of potato tuber formation in vitro. |
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