Japanese hop (Humulus japonicus Siebold & Zucc.) was karyotyped by chromosome measurements, fluorescence in situ hybridization with rDNA and telomeric probes, and C-banding/DAPI. The karyotype of this species consists of sex chromosomes (XX in female and XY1Y2 in male plants) and 14 autosomes difficult to distinguish by morphology. The chromosome complement also shows a rather monotonous terminal distribution of telomeric repeats, with the exception of a pair of autosomes possessing an additional cluster of telomeric sequences located within the shorter arm. Using C-banding/DAPI staining and 5S and 45S rDNA probes we constructed a fluorescent karyotype that can be used to distinguish all autosome pairs of this species except for the 2 largest autosome pairs, lacking rDNA signals and having similar size and DAPI-banding patterns. Sex chromosomes of H. japonicus display a unique banding pattern and different DAPI fluorescence intensity. The X chromosome possesses only one brightly stained AT-rich terminal segment, the Y1 has 2 such segments, and the Y2 is completely devoid of DAPI signal. After C-banding/DAPI, both Y chromosomes can be easily distinguished from the rest of the chromosome complement by the increased fluorescence of their arms. We discuss the utility of these methods for studying karyotype and sex chromosome evolution in hops.

Endosperm is an interesting model for in vitro experiments, because of its unique origin, development and ploidy level. Here we used Actinidia deliciosa endosperm-derived callus to investigate morphology, histology and chemistry of extracellular matrix (ECM) structures in morphogenically stable tissue from long - term culture. SEM and TEM analysis showed that ECM is a heterogenous layer which consists of amorphous, dark – staining material, osmiophilic granules and reticulated fibres outside the outer callus cell wall. This structure may serve as a structural marker of morphogenic competence in endosperm – derived callus, because of its presence on the surface of callus forming morphogenic domains and its disappearance during organ growth. Based on immunolabelling, histochemistry, solvent and enzyme treatments, we suggest that pectins and lipids are components of the ECM layer. These results might indicate protective, water retention and/or cell communication functions for this ECM layer. Addendum to: Popielarska-Konieczna M, Kozieradzka-Kiszkurno M, Świerczyńska J, Góralski G, Ślesak H, Bohdanowicz J. Ultrastructure and histochemical analysis of extracellular matrix surface network in kiwifruit endosperm-derived callus culture. Plant Cell Rep 2008; 27:1137-45.

We compared chromosome number (CN) variation among vascular floras of three different countries with increasing latitude in the Boreal hemisphere: Italy, Slovak

Helianthus tuberosus is economically important species. To improve characters of this energetic plant via genetic modification, production of callus tissue and plant regeneration are the first steps. A new, potentially energetic cultivar Albik was used in this study to test callus induction and regeneration. Callus was produced on leaves, petioles, apical meristems and stems from field-harvested plants but was totally non-morphogenic. Its induction started in the cortex and vascular bundles as confirmed by histological analysis. The surface of heterogeneous callus was partially covered with a membranous extracellular matrix surface network visible in scanning and transmission electron microscopies. The results clearly indicate that: (i) the morphogenic capacity of callus in topinambur is genotype dependent, (ii) cv. Albik of H. tuberosus proved recalcitrant in in vitro regeneration, and (iii) extracellular matrix surface network is not a morphogenic marker in this cultivar.