Search

A high-efficiency somatic embryogenesis protocol of Japanese larch (Larix leptolepis Gordon) has been established in our investigation. Calli were induced from immature zygotic embryos of female cones of L. leptolepis and then subcultured regularly on to a modified Gupta and Durzan (DCR) basal medium for 5 years. Embryogenic tissues showed distinct morphological changes during somatic embryo development when they were transferred to a maturation medium supplemented with abscisic acid (ABA) compared with the morphology in a medium lacking ABA. Histological observations indicated that polyembryony was a characteristic feature during early embryogeny and somatic embryos at later stages showed normal histodifferentiation. In addition, histochemical analysis revealed that abundant starch granules and proteins accumulated in mature embryos, indicating that they played important roles in the development and regeneration of normal plantlets from somatic embryos on hormone-free germination media

The XY sex-determination system is crucial for plant reproduction. However, little is known about the mechanism of the origin and evolution of the XY sex chromosomes. It has been believed that a pair of autosomes is evolved to produce young sex chromosomes (neo-X chromosome and neo-Y chromosome) by loss of function or gain of function mutation, which influences the development of pistil or stamen. With the aggravation of the recombination suppression between neo-X and neo-Y and consequent expanding of the non-recombination region, the proto-sex chromosomes were finally developed to heteromorphic sex chromosomes. Accumulation of repetitive sequences and DNA methylation were probably involved in this process. Transposons, as the most abundant repetitive sequences in the genome, might be the initial motivation factors for the evolution of sex chromosome. Moreover, transposons may also increase heterochromatin expansion and recombination suppression of sex chromosome by local epigenetics modification. In this review, we summarize the function of transposon accumulation and the relationship between transposon and heterochromatization in the evolution of plant sex chromosome.

The species of Osmanthus are important gardening plants. But the systematic classification on the molecular level is still not clear. The ISSR (Inter-simple sequence repeat) marker may provide good research evidence for the relationships of the species. In this study, reaction system, based on ISSR analysis in Osmanthus., was optimized by gradient PCR examination, and the optimal reaction system was established: 20-100ng template DNA, 2.0mmol/L Mg2+, 0.4umol/L primer, 200umol/L dNTP and 0.5U-1U TaqDNA polymerase. A total of 15 ISSR primers were screened in nine Osmanthus Lour. species, of which 4 polymorphic and informative patterns were selected to determine the genetic diversity. ISSR marker analysis suggests that 4 ISSR primers generated a total number of 52 ISSR locus, of which 51 locus were polymorphic, and the percentage polymorphic locus was 98.5%. UPGMA dendrogram showed that these 9 species could be classified into 3 groups: O.cooperi, O.heterophyllus, O.×fortunei; O.yunnanensis; O.fordii, O.henryi, O.delavayi, O.matsumuraanus and O.armatus. The ISSR markers are thus useful in understanding the evolutionary relationships of Osmanthus.

The random amplified polymorphic DNA (RAPD) technique was used to amplify DNA fragment ,aiming at finding markers linked to the sex determination in Ginkgo biloba L. Of the 158 RAPD bands , only a 1080 bp RAPD marker generated by aprimer (S2) of random sequence ,which was found to be associated with the male plants. which was abundant in AT and also used to design flanking 24-mer oligonucleotide SCAR primers SCS2-1 and SCS2-2. Both of these SCARs amplified a single 1080bp fragment; the same size as the cloned RAPD fragment. This SCAR marker proved to be suitable for precise and rapid identification of male plants in the early stages for breeding programs.

The perianth DNA extraction methods were discussed as Lycoris longituba for example. By means of RAPD and ISSR, germplasmic resources of Lycoris longituba were primarily studied. The results were as follow: by RAPD, a total of 77 discernible loci were obtained using 12 primers, of which 53 loci were polymorphic (PPB = 68.8%); by ISSR, 67 discernible loci were got using 9 primers, of which 62 loci were polymorphic (PPB = 92.5%). So, genetic diversity of Lycoris longituba was abundant, whose germplasmic resources could be stored for breeding. From UPGMA dendrogram of Lycoris longituba using RAPD or ISSR method, three Lycoris longituba types were supported with molecular evidence, which were originally distinguished by flower color. Therefore, in the future use of Lycoris longituba germplasmic resources, different varieties of Lycoris longituba could be cultivated.

The hypocotyl and cotyledon of Brassica napus L. H165 and Brassica juncea DB3 were transformed with chitinase gene and herbicide-resistance gene by co-culture with Agrobacterium tumefacients LBA4404, and rape plants were obtained which could grow on the medium containing herbicide. The PCR result showed that exotic genes were integrated in the genome of the rape. Further study was performed to determine the impact of temperature on the transgenic rate and the differentiation of explants.

A new binary vector, pAM12-S1m, harboring the aroAM12 gene encoding for 5-enolpyruvyl- shikimate- 3-phosphate synthase (EPSPS) and a synthetic recombinant BtS1m toxin gene consisting of 331 N-terminal amino acids of CryIAc and 284 C-terminal amino acids of CryIAb has been constructed. The truncated aroAM12 gene, which was obtained through gene shuffling technology, was ligated with a transit sequence of Arabidopsis EPSPS and expressed in cotton plants driven by cauliflower mosaic virus 35S (CaMV35S) promoter. The chimeric BtS1m toxin gene was fused with DNA sequence encoding PR1b secretary signal peptide and expressed under the control of 2E-35S promoter and “ȍ” translation enhancer sequence derived from tobacco mosaic virus. The mutant EPSPS of aroAM12 gene product conferring highly resistant to glyphosate, the active ingredient in herbicide Roundup ® , was used as a dominant selectable marker for cotton plant transformation. The genes were introduced into commercial cultivar Zhongmian12 of cotton (Gossypium hirsutum L.) by Agrobacterium-mediated transformation. The transformants were directly selected on medium supplemented with 80μmol/L glyphosate. In this research, 40 regenerative cotton plantlets were obtained through screening. Integration of aroAM12 and Bts1m genes was confirmed by PCR and Southern blot, the results indicated that all the 40 plants possessed the aroAM12 gene, 28 of which possessed both the aroAM12 and BtS1m genes. Expression of both the genes was established by Western blots. Insect bioassay and glyphosate resistance assay indicated that the transgenic cotton plants obtained were highly resistant to glyphosate and insect. The results of glyphosate resistance and insect bioassay of T1 generation showed that the numbers of resistance and sensitive phenotypes showed Mendelian segregation ratio.