No abstract

Broad phenotypic variations were induced in derivatives of an asymmetric somatic hybridization of bread wheat (Triticum aestivum) and tall wheatgrass (Thinopyrum ponticum Podp); however, how these variations occurred was unknown. We explored the nature of these variations by cytogenetic assays and DNA profiling techniques to characterize six genetically stable somatic introgression lines. Karyotyping results show the six lines similar to their wheat parent, but GISH analysis identified the presence of a number of short introgressed tall wheatgrass chromatin segments. DNA profiling revealed many genetic and epigenetic differences, including sequences deletions, altered regulation of gene expression, changed patterns of cytosine methylation, and the reactivation of retrotransposons. Phenotypic variations appear to result from altered repetitive sequences combined with the epigenetic regulation of gene expression and/or retrotransposon transposition. The extent of genetic and epigenetic variation due to the maintenance of parent wheat cells in tissue culture was assessed and shown to be considerably lower than had been induced in the introgression lines. Asymmetric somatic hybridization provides appropriate material to explore the nature of the genetic and epigenetic variations induced by genomic shock.KEYWORDS bread wheat; asymmetric somatic hybridization; introgression line; genomic shock, genetic and epigenetic alteration W ITH the world's population continuing to increase, achieving a sustainable mode of food production represents an ever-growing challenge. Plant breeding has narrowed the genetic base of many crop species, but as yet has had little impact on the genetic diversity present in their wild relatives. In principle, this diversity can be introgressed into crops via sexual hybridization and subsequent backcrossing. However, in practice, wild-crop manipulation has been severely restricted by difficulties in creating the initial sexual hybrid and by sterility issues in the early backcross generations (Xia 2009). Asymmetric somatic hybridization is a viable alternative to introgression, especially where wide crosses are not feasible. It has been successfully exploited in bread wheat to transfer chromosomal segments from a number of related species Xiang et al. 2003Xiang et al. , 2004Cheng et al. 2004;Zhou and Xia 2005;Xia 2009). More importantly, asymmetric somatic hybridization offers smaller alien chromatin introgression, thereby overcoming a significant problem in wheat sexual hybrids where the Ph1 gene prevents homeologous recombination (Griffiths et al. 2006).Newly synthesized allopolyploids have provided an opportunity to explore the nature of the genetic and epigenetic changes triggered by polyploidization (Song et al. 1995;Comai et al. 2000;Ozkan et al. 2001;Shaked et al. 2001;Madlung et al. 2002;Han et al. 2003;Ma et al. 2004;Wang et al. 2004a;Salmon et al. 2005;Tate et al. 2006;Bassene et al. 2010;Xu et al. 2014), although a few allopolyploids were not accompanied with such changes (Liu...

Chemical structures of typical Solanum steroidal glycoalkaloids from eggplant, tomato, and potato.

Dendrobium is a genus of flowering plants belonging to the Orchidaceae family with more than 1,400 species. Many Dendrobium species have been used as medicinal plants in several Asian countries for thousands of years. Alkaloids were reported as the major biological markers due to their complex chemical compositions and various types. In this review, we summarized the structural types of alkaloids, their pharmacological activities, as well as the mechanisms of biological activities. More than sixty alkaloids were isolated and identified from the Dendrobium genus. Moreover, the pharmacological effects of Dendrobium alkaloids as hepatic lipid and gluconeogenesis regulation, as neuroprotection, and as anti-tumor, anti-inflammatory, anti-diabetes, and anti-virus factors were described. Besides, the total chemical synthesis of dendrobine is provided, while the biosynthetic pathway of dendrobine has been proposed based on the functions of associated genes. For applications of these invaluable herbs, more researches on the extraction of biological markers from compounds are needed. Further confirmation of the proposed biosynthetic pathways is anticipated as well.

Melatonin can increase plant resistance to stress, and exogenous melatonin has been reported to promote stress resistance in plants. In this study, a melatonin biosynthesis-related SlCOMT1 gene was cloned from tomato (Solanum lycopersicum Mill. cv. Ailsa Craig), which is highly expressed in fruits compared with other organs. The protein was found to locate in the cytoplasm. Melatonin content in SlCOMT1 overexpression transgenic tomato plants was significantly higher than that in wild-type plants. Under 800 mM NaCl stress, the transcript level of SlCOMT1 in tomato leaf was positively related to the melatonin contents. Furthermore, compared with that in wild-type plants, levels of superoxide and hydrogen peroxide were lower while the content of proline was higher in SlCOMT1 transgenic tomatoes. Therefore, SlCOMT1 was closely associated with melatonin biosynthesis confers the significant salt tolerance, providing a clue to cope with the growing global problem of salination in agricultural production.