Meiotic behaviour and morpho-phenological variation in cut stock (Matthiola incana L.) flower

Morpho-phenological and meiotic studies were performed in twelve cultivars of Matthiola incana. All of the cultivars were diploid (2n = 2x = 14) with basic chromosome number x = 7. A number of aneuploid PMCs (n + 1) were observed in plants of two cultivars, named ‘Nobel’ (NB) and ‘Goddess’ (GD), at the diakinesis stage. Trisomic individuals with the frequency of 20% and 5% and (2n + 1 = 15) somatic chromosomes were observed in seeds obtained from single-flowered plants of the cultivars NB and GD, respectively. An additional chromosome was mostly observed in the form of a chain trivalent or a rod univalent. Various meiotic abnormalities were found in all the cultivars to different degrees. In these cultivars, the percentage of cells with meiotic abnormalities was higher in anaphase I. Cytomixis was observed for the first time in Matthiola incana. ANOVA tests revealed significant differences in morpho-phenological characteristics. ‘Nobel’ differs from the others in all of the vegetative features investigated in this study. All the cultivars studied except ‘Nobel’ and ‘Pacific Crimson’ possessed high pollen fertility (> 90%). Five groups of the cultivars based on morpho-phenological features disagree with the clustering of cultivars based on meiotic traits. It is thought that the various morpho-phenological features observed among the cultivars could be due to their different genetic background and not only to meiotic anomalies.

Cytotaxonomic Study of Hypodematium (Hypodematiaceae) from China

Chromosome numbers and reproductive biology of nine species of the fern genus Hypodematium (Hypodematiaceae) from China were investigated. The chromosome numbers of eight species are reported here for the first time: H. daochengensis n=41 (41 II); H. fordii n=40 (40 II), n=80 (40 II+40 I), 2n=120; H. glanduloso-pilosum n=41 (41 II), 2n=82, 2n=123; H. gracile n=41 (41 II); H. hirsutum n= 41 (41 II); H. microleptoides n=41 (41 II); H. sinense n= 40 (40 II) and H. squamuloso-pilosum n=41 (41 II). Two cytotypes, n=82 (41 II+41 I) and 2n=123 in H. crenatum, are reported for the first time. Our results showed that the species with these cytotypes are agamospermous triploids: H. crenatum n = 82 (41 II +41 I), H. glanduloso-pilosum n = 82 (41 II +41 I) and H. fordii n = 80 (40 II +40 I), based on the unequal size and presence of aborted spores in the sporangium, and the allotriploid hybrid chromosomes in the spore mother cell at the diakinesis stage of meiosis I. The remaining species are sexual diploids and tetraploids, based on the chromosome number n = 41 and n =82 at the diakinesis stage of meiosis I of spore mother cells. The relationships among habitat preferences, frond hairs and reproductive modes in Hypodematium are discussed and illustrated. It appears that plants with large fronds and sparse, thin hairs, living in humid and shady places undergo sexual reproduction, while small plants living in sunny and dry conditions with thick hairs undergo agamospermous reproduction. The distribution pattern and basic chromosome number all indicated the basic chromosome number x= 41 was plesiomorphic, whereas x=40 was apomorphic. Chromosome aneuploid changes occurred in this genus. The distribution of the sexual diploids and tetraploids and agamospermous triploids suggests that the genus might have originated in the Himalayas and dispersed from there to northeast Asia and Japan.

Induction of 2n pollen by colchicine in Populus × popularis and its triploids breeding

Induction of 2n pollen is a required technique for cultivating polyploid via sexual polyploidy. Orthogonal design or Taguchi Design was applied to select the best treatment process of 2n pollen induction inPopulus×popularisfrom different levels of the meiosis stage of male flower buds, colchicine concentration, times of injection, and interval between injections. Flow cytometry and chromosome counting were used to identify the triploids from the offspring ofP.×euramericana. (Dode) Guinier pollinated with induced pollen ofP.×popularis. The results showed that high 2n pollen rate can be achieved by selecting the flower buds during diakinesis stage in meiosis, and then injecting 0.6% colchicine 4 times with 2 hours interval. The 2n pollen rate reached 62.10% by this process, and two triploids were obtained, which indicates that it is possible for cultivating triploids via 2n pollen induction by colchicine treatment in poplar. Results and protocol related to 2n pollen induction, polyploid identification and effect of 2n pollen in this study might be applicable in polyploidy breeding in sectionAigeirosandTacamahacaof poplar.

309CHROMOSOME CONDENSATION IS CORRELATED WITH HISTONE H3 PHOSPHORYLATION WITHOUT CDC2 KINASE AND MAP KINASE ACTIVITIES IN PIG OOCYTES

Chromosome condensation is the first step of oocyte maturation. When the oocytes resume meiosis, chromosomes start to condense and Cdc2 kinase becomes activated. However, recent findings show that the chromosome condensation does not always correlate with Cdc2 kinase activity in pig oocytes. The objectives of this study were to examine (1) the correlation between chromosome condensation and histone H3 phosphorylation at serine 10 (Ser10) during meiotic maturation of pig oocytes, and (2) the effects of protein phosphatase 1/2A (PP1/PP2A) inhibitors on the chromosome condensation and the involvement of Cdc2 kinase, MAP kinase and histone H3 kinase in this process. Oocyte-cumulus-granulosa cell complexes (OCGCs) were collected from follicles of 4–6mm in diameter. OCGCs were cultured in modified TCM 199 for different periods of time to obtain oocytes at the germinal vesicle (GV, 0h), diakinesis (18h), metaphase I (24–27h), anaphase I to telophase I (30–33h), and metaphase II (42h) stages. To examine the effects of PP1/PP2A inhibitors on the chromosome condensation, oocyte-cumulus-complexes (OCCs) were cultured in modified TCM 199 with either 2.5μM okadaic acid (OA) or 50nM calyculin A (CL-A) for 0.5, 1, 2, 3, 4 and 6h. To inhibit the MAP kinase activity in the oocytes treated with the PP1/PP2A inhibitor, OCCs were cultured in medium containing CL-A and the MEK inhibitor, U0126 (0.1mM). Morphology of the chromosome and nuclear membrane, and phosphorylation of histone H3 were examined by the immunofluorescent microscopy. In each group 30 oocytes were examined for OA or CL-A and 60 oocytes for CL-A+U0126 treatments. Activities of Cdc2 kinase, MAP kinase and histone H3 kinase were also examined. Phosphorylation of histone H3 (Ser10) was not detected in the oocytes at the GV stage. The phosphorylation was first detected in the clump of condensed chromosomes at the diakinesis stage of prophase I and maintained until metaphase II. The kinase assay also showed that histone H3 kinase activity was low in GV oocytes, increased at the diakinesis stage, and then maintained high activity until metaphase II. PP1/PP2A inhibitors induced rapid chromosome condensation in pig oocytes. Histone H3 phosphorylation (Ser10) became detectable together with the chromosome condensation in the treated oocytes after 2h. After 6h, oocytes had highly condensed chromosomes with phosphorylated histone H3 (81% in CL-A- and 71% in OA-treated oocytes). Both histone H3 kinase and MAP kinase were activated in the treated oocytes, although Cdc2 kinase was not activated. In the oocytes treated with CL-A and U0126, neither Cdc2 kinase nor MAP kinase were activated, although histone H3 kinase was still activated and chromosomes condensed. These results suggest that phosphorylation of histone H3 (Ser10) occurs in condensed chromosomes during maturation in pig oocytes. Futhermore, the chromosome condensation is correlated with histone H3 kinase activity, but not with Cdc2 kinase and MAP kinase activities.

Two well-known mutants of chiasma maintenance function in maize are allelic

By a series of traditional crosses, allelism has been tested for two maize recessive mutants of independent origin, dy1 and dsy1, both called desynaptic. These mutants both display loss of chiasmate association during diakinesis (late prophase I) but at differing frequencies. This chiasma loss happens before nucleolar loss and nuclear membrane system breakdown. That crossovers have occurred to establish the chiasmata in the first place has been documented by diakinesis-stage separation of heterozygous heterochromatic regions in univalents formed by bivalent-association breakdown. In the present work, the two mutants have been found to be allelic by the outcome of traditional crosses that produced variant plants which were heterozygous for the two alleles. These plants express a unique phenotype at diakinesis, but are essentially normal at pachytene, metaphase I, anaphase I, and later stages of meiosis.Key words: chiasma, crossover, complementation.

Protostrongylus rufescens: a cytogenetic study

ABSTRACTThe diploid chromosome number of Protostrongylus rufescens is 2n=11 for males and 2n=12 for females. So, the sex determinism mechanism is XO/XX. The study of the genetic behaviour of this species has been made. In diakinesis stage the bivalents show typical tetrads with cross, Ø, and lineal configurations. The division of the sexual chromosome is prereductional for the first meiotic division.