Molecular Cytogenetics of Pisum sativum L. Grown under Spaceflight-Related Stress

Investigating the Origin and Evolution of Polyploid Trifolium medium L. Karyotype by Comparative Cytogenomic Methods

Trifolium medium L. is a wild polyploid relative of the agriculturally important red clover that possesses traits promising for breeding purposes. To date, T. medium also remains the only clover species with which agriculturally important red clover has successfully been hybridized. Even though allopolyploid origin has previously been suggested, little has in fact been known about the T. medium karyotype and its origin. We researched T. medium and related karyotypes using comparative cytogenomic methods, such as fluorescent in situ hybridization (FISH) and RepeatExplorer cluster analysis. The results indicate an exceptional karyotype diversity regarding numbers and mutual positions of 5S and 26S rDNA loci and centromeric repeats in populations of T. medium ecotypes and varieties. The observed variability among T. medium ecotypes and varieties suggests current karyotype instability that can be attributed to ever-ongoing battle between satellite DNA together with genomic changes and rearrangements enhanced by post-hybridization events. Comparative cytogenomic analyses of a T. medium hexaploid variety and diploid relatives revealed stable karyotypes with a possible case of chromosomal rearrangement. Moreover, the results provided evidence of T. medium having autopolyploid origin.

Metabolomics Analysis in Different Development Stages on SP0 Generation of Rice Seeds After Spaceflight

Spaceflight is a special abiotic stress condition. In recent years, it has been confirmed that the spaceflight caused the stress response of rice seeds, and the protein level, transcription level, and methylation level will change during the planting process after returning to the ground. However, the changes at the metabolome level are not very clear. In this study, two kinds of rice seeds, Dongnong423 (DN3) and Dongnong416 (DN6), were carried on the ShiJian-10 retractable satellite (SJ-10) for 12.5 days in orbit, returned to the ground and planted in the field until the three-leaf (TLP) and tillering stage (TS). The results of antioxidant enzyme activity, soluble sugar, and electron leakage rate revealed that the spaceflight caused the stress response of rice. The TLP and TS of DN3 identified 110 and 57 different metabolites, respectively, while the TLP and TS of DN6 identified 104 and 74 different metabolites, respectively. These metabolites included amino acids, sugars, fatty acids, organic acids and secondary metabolites. We used qRT-PCR technology to explore the changes of enzyme genes in the tricarboxylic acid cycle (TCA) and amino acid metabolism pathway. Combined with the results of metabolomics, we determined that during the TLP, the TCA cycle rate of DN3 was inhibited and amino acid metabolism was activated, while the TCA cycle rate of DN6 was activated and amino acid metabolism was inhibited. In TS, the TCA cycle rate of DN3 was inhibited, and amino acid metabolism was not significantly changed, while the TCA cycle rate of DN6 was activated and amino acid metabolism was inhibited. These results suggested that the response mechanisms of the two different rice strains to spaceflight stress are different, and these differences may be reflected in energy consumption and compound biosynthesis of rice in different growth and development stages. This study provided new insights for further exploring the effects of spaceflight.

Molecular Cytogenetics of Eurasian Species of the Genus Hedysarum L. (Fabaceae)

The systematic knowledge on the genus Hedysarum L. (Fabaceae: Hedysareae) is still incomplete. The species from the section Hedysarum are valuable forage and medicinal resources. For eight Hedysarum species, we constructed the integrated schematic map of their distribution within Eurasia based on currently available scattered data. For the first time, we performed cytogenomic characterization of twenty accessions covering eight species for evaluating genomic diversity and relationships within the section Hedysarum. Based on the intra- and interspecific variability of chromosomes bearing 45S and 5S rDNA clusters, four main karyotype groups were detected in the studied accessions: (1) H.arcticum, H. austrosibiricum, H. flavescens, H. hedysaroides, and H. theinum (one chromosome pair with 45S rDNA and one pair bearing 5S rDNA); (2) H. alpinum and one accession of H. hedysaroides (one chromosome pair with 45S rDNA and two pairs bearing 5S rDNA); (3) H. caucasicum (one chromosome pair with 45S rDNA and one chromosome pair bearing 5S rDNA and 45S rDNA); (4) H. neglectum (two pairs with 45S rDNA and one pair bearing 5S rDNA). The species-specific chromosomal markers detected in karyotypes of H. alpinum, H. caucasicum, and H. neglectum can be useful in taxonomic studies of this section.