No abstract

To investigate the molecular mechanisms underlying the low fibroin production of the ZB silkworm strain, we used both SDS-PAGE-based and gel-free-based proteomic techniques and transcriptomic sequencing technique. Combining the data from two different proteomic techniques was preferable in the characterization of the differences between the ZB silkworm strain and the original Lan10 silkworm strain. The correlation analysis showed that the individual protein and transcript were not corresponded well, however, the differentially changed proteins and transcripts showed similar regulated direction in function at the pathway level. In the ZB strain, numerous ribosomal proteins and transcripts were down-regulated, along with the transcripts of translational related elongation factors and genes of important components of fibroin. The proteasome pathway was significantly enhanced in the ZB strain, indicating that protein degradation began on the third day of fifth instar when fibroin would have been produced in the Lan10 strain normally and plentifully. From proteome and transcriptome levels of the ZB strain, the energy-metabolism-related pathways, oxidative phosphorylation, glycolysis/gluconeogenesis, and citrate cycle were enhanced, suggesting that the energy metabolism was vigorous in the ZB strain, while the silk production was low. This may due to the inefficient energy employment in fibroin synthesis in the ZB strain. These results suggest that the reason for the decreasing of the silk production might be related to the decreased ability of fibroin synthesis, the degradation of proteins, and the inefficiency of the energy exploiting.

A double haploid population, which consists of 127 lines derived from anther culture of a typical indica and japonica hybrid ÔZYQ8Õ/ÔJX17Õ, was used in this study. Seed storability was investigated by using the storage property measured by the difference of seed germination rates before and after treatment of the rice seeds under 40°C and 95% relative humidity for 10 days in a phytotron. Three QTLs related to rice seed storability were detected on chromosomes 9, 11 and 12, with the LOD scores 2.76, 4.83 and 2.54, respectively, together explaining 35.4% of the genetic variation. The ÔJX17Õ allele at qLS-9 and the ÔZYQ8Õ alleles at qLS-11 and qLS-12 could enhance the rice seed storability. The effects of the ÔZYQ8Õ alleles of qLS-11 and qLS-12 were also verified using chromosome segment substitution lines.

Spider dragline silk is a remarkable material that shows excellent mechanical properties, diverse applications, biocompatibility and biodegradability. Transgenic silkworm technology was used to obtain four types of chimeric silkworm/spider (termed composite) silk fibres, including different lengths of recombinant Major ampullate Spidroin1 (re-MaSp1) or recombinant Major ampullate Spidroin2 (re-MaSp2) from the black widow spider, Latrodectus hesperus. The results showed that the overall mechanical properties of composite silk fibres improved as the re-MaSp1 chain length increased, and there were significant linear relationships between the mechanical properties and the re-MaSp1 chain length (p < 0.01). Additionally, a stronger tensile strength was observed for the composite silk fibres that included re-MaSp1, which only contained one type of repetitive motif, (GA)n/An, to provide tensile strength, compared with the silk fibres that includedre-MaSp2, which has the same protein chain length as re-MaSp1 but contains multiple types of repetitive motifs, GPGXX and (GA)n/An. Therefore, the results indicated that the nature of various repetitive motifs in the primary structure played an important role in imparting excellent mechanical properties to the protein-based silk fibres. A silk protein with a single type of repetitive motif and sufficiently long chains was determined to be an additional indispensable factor. Thus, this study forms a foundation for designing and optimizing the structure of re-silk protein using a heterologous expression system.