In the course of reconstructing Aegilops caudata from its own genome (CC) and its plasmon, which had passed half a century in common wheat (genome AABBDD), we produced alloplasmic Ae. cylindrica (genome CCDD) with the plasmon of Ae. caudata. This line, designated (caudata)-CCDD, was found to express male sterility in its second substitution backcross generation (SB2) of (caudata)-AABBCCDD pollinated three times with the Ae. cylindrica pollen. We repeatedly backcrossed these SB2 plants with the Ae. cylindrica pollen until the SB5 generation, and SB5F2 progeny were produced by self-pollination of the SB5 plants. Thirteen morphological and physiological characters, including pollen and seed fertilities, of the (caudata)-CCDD SB5F2 were compared with those of the euplasmic Ae. cylindrica. The results indicated that the male sterility expressed by (caudata)-CCDD was due to genetic incompatibility between the Ae. cylindrica genome and Ae. caudata plasmon that did not affect any other characters of Ae. cylindrica. Also, we report that the genome integrity functions in keeping the univalent transmission rate high.
We dissected barley chromosomes 1H and 6H added to common wheat by the gametocidal system and identified structural changes of the chromosomes by fluorescence in situ hybridization and genomic in situ hybridization. We found five aberrations of chromosome 1H, all of which lacked the long arm: one small fragment with the subtelomeric HvT01 sequence, one terminal deletion, and three telocentric chromosomes of the short arm. We established 33 dissection lines carrying single aberrant 6H chromosomes, of which 15 were deletions, 16 were translocations and two were isochromosomes. We conducted PCR analysis of the aberrant barley chromosomes using 75 and 81 EST markers specific to chromosomes 1H and 6H, respectively. This enabled us to construct a cytological map of chromosome 6H and to compare it to the previously reported genetic map and also to the physical map, which were released by the International Barley Genome Sequencing Consortium. The marker orders on the three maps were largely in agreement. The cytological map had better resolution in the proximal region of chromosome 6H than the corresponding genetic map. We discuss some of the discrepancies in marker order between the three maps that might be due to intraspecific polymorphism and gene duplication, as well as to technical problems inherent in the physical mapping process.
Allopolyploidization is an important evolutionary event in plants, but its genome-wide effects are not fully understood. Common wheat, Triticum aestivum (AABBDD), evolved through amphidiploidization between T. turgidum (AABB) and Aegilops tauschii (DD). Here, global gene expression patterns in the seedlings of a synthetic triploid wheat line (ABD), its chromosome-doubled hexaploid (AABBDD) and stable synthetic hexaploid (AABBDD), and the parental lines T. turgidum (AABB) and Ae. tauschii (DD) were compared using an oligo-DNA microarray to identify metabolic pathways affected by the genome conflict that occurs during allopolyploidization and genome stabilization. Characteristic gene expression patterns of non-additively expressed genes were detected in the newly synthesized triploid and hexaploid, and in the stable synthetic hexaploid. Hierarchical clustering of all differentially expressed and non-additively expressed genes revealed that the gene expression patterns of the triploid (ABD) were similar to those of the maternal parent (AABB), and that expression patterns in successive generations arising from self-pollination became closer to that of the pollen parent (DD). The non-additive gene expression profiles markedly differed between the triploid (ABD) and chromosome-doubled hexaploid (AABBDD), as supported by Gene Ontology (GOSlim) analysis. Four hundred and nineteen non-additively expressed genes were commonly detected in all three generations. GOSlim analysis indicated that these non-additively expressed genes were predominantly involved in “biological pathways”. Notably, four of 11 genes related to sugar metabolism displayed elevated expression throughout allopolyploidization. These may be useful candidates for promoting heterosis and adaptation in plants.
The water deer (Hydropotes inermis) is one of the rarest species of deer in the family Cervidae. Only two subspecies exist in East Asia, and few studies have examined the genetic characteristics of the species. Here, we investigated the genetic diversity, phylogeny and population differentiation of the Korean subspecies (H. inermis argyropus). Seventeen mitochondrial D-loop haplotypes (822 bp) were detected and analyzed from 107 individual samples, together with a Chinese subspecies (H. inermis inermis) haplotype. The genetic diversity of the Korean subspecies is lower (π = 0.756%, h = 0.867) than that of the Chinese subspecies estimated in a previous study. This low genetic diversity may result from historical anthropogenic disturbances and/or a founder effect during the glacial period. The phylogenetic tree and median-joining network showed no location-specific distribution of D-loop haplotypes, but revealed two major lineages, A and B, of water deer. The A and B lineages were separated from each other at the beginning of the Pleistocene era (2.1–1.3 million years ago), with a genetic divergence of 1.332 ± 0.340%. The genetic divergence within lineages A and B was 0.525 ± 0.167% and 0.264 ± 0.113%, respectively. This suggests that climate change affected the division of the two lineages. Water deer sampled from the three Korean regions (26 locations) were slightly distinct in their genetic structure (AMOVA: FST = 0.28416, P < 0.00001; ΦST = 0.19239, P < 0.00001). Such slight population differentiation may be derived from differential dispersal ability in males and females. The use of genetic markers, such as nuclear microsatellite and Y-linked DNA markers, and samples collected from various localities in East Asia should improve our understanding of the water deer’s genetic characteristics.
Although molecular phylogenetics is a strong tool for reconstructing the tree of life, many problems persist due to systematic errors caused by model mis-specifications. Resolving misconstructed trees should lead us to better understand the processes of molecular evolution. Mammalian mitogenomes provide us with a good opportunity in this respect, because the mammalian tree is well established on the basis of multiple nuclear genes, and mitogenome trees are sometimes in conflict with it, for example concerning the positions of tarsiers and colugos. The utility of mitogenomes as a phylogenetic marker is therefore sometimes questioned, and an important problem is whether any method can overcome the misleading phylogenetic signals of mitogenomes. Here we show that the maximum likelihood tree of 463 eutherian mitogenomes reconstructed from nucleotide sequences of protein-encoding genes gives positions of tarsiers and colugos that are consistent with the well-established nuclear tree; this is the first study to obtain a consistent tree with respect to the positions of tarsiers and colugos using mitogenomes. Furthermore, our mitogenome tree of the 463 eutherians is mostly consistent with the nuclear gene tree. Previous mitogenomic studies have been hampered by sparse taxon sampling, and our analysis demonstrates the importance of dense taxon sampling to relieve the misleading phylogenetic signals of mitogenomes. However, because there are many convergent and parallel substitutions in the amino acid sequences, the effect of dense taxon sampling on the accuracy of tree reconstruction seems to be very limited. We further show the importance of using synonymous substitutions with dense taxon sampling as well as with appropriate modeling in recovering the well-established tree from lower to even higher levels of eutherian phylogeny.