Influence of a heavy-metal-polluted environment on Viola tricolor genome size and chromosome number

Intraspecific changes in genome size and chromosome number lead to divergence and species evolution. Heavy metals disturb the cell cycle and cause mutations. Areas contaminated by heavy metals (metalliferous sites) are places where microevolutionary processes accelerate; very often only a few generations are enough for a new genotype to arise. This study, which continues our long-term research on Viola tricolor (Violaceae), a species occurring on both metalliferous (Zn, Pb, Cd, Cu) and non-metalliferous soils in Western and Central Europe, is aimed at determining the influence of environments polluted with heavy metals on genome size and karyological variability. The genome size of V. tricolor ranged from 3.801 to 4.203 pg, but the differences between metallicolous and non-metallicolous populations were not statistically significant. Altered chromosome numbers were significantly more frequent in material from the polluted sites than from the non-polluted sites (43% versus 28%). Besides the standard chromosome number (2n = 26), aneuploid cells with lower (2n = 18–25) or higher (2n = 27, 28) chromosome numbers were found in plants from both types of site, but polyploid (2n = 42) cells were observed only in plants from the metalliferous locality. The lack of correlation between chromosome variability in root meristematic cells and genome size estimated from peduncle cells can be attributed to elimination of somatic mutations in generative meristem, producing chromosome-stable non-meristematic tissues in the peduncle

Přirozená hybridizace mezi Gladiolus palustris and G. imbricatus, zjištěná na základě morfologických, molekulárních a reprodukčních znaků

While studying the extremely rare species, Gladiolus palustris, in Poland, putative hybrid plants were discovered. Natural hybridization between G. palustris and G. imbricatus was confirmed by chloroplast (psbA-trnH and rpl32-trnL) DNA and nuclear ribosomal DNA (ITS1) sequences AFLP markers and macro-, micromorphological and reproductive characters. Based on molecular data, the hybridization events are likely to have occurred relatively recently with G. palustris as the maternal species and G. imbricatus as the pollen donor in interspecific crosses. The existence of a shared common cpDNA haplotype in all hybrids and G. palustris indicates unidirectional hybridization. A new nothospecies, G. ×sulistrovicus, is described. Analyses of AFLP data and polymorphisms of ITS1 sequences showed additive inheritance of parental genomic fragments in G. ×sulistrovicus. The hybrids exhibited either morphological similarity to G. imbricatus or intermediateness in phenotypic characters. The corm structure of flowering plants and seed capsules clearly distinguish the hybrid. The new taxon is characterized by a lower generative reproduction than the parental species, however hybrids produce ~50% viable pollen and seeds, which allows them to produce subsequent hybrid generations. The weak generative reproduction was enhanced by highly efficient vegetative propagation. The western part of the Balkan Peninsula and adjacent areas (Croatia, Bosnia and Hercegovina, Serbia, northern Italy) and central Europe (Poland, the Czech Republic, Slovakia, eastern Austria, Hungary) are the most likely areas where G. ×sulistrovicus will occur. Hybridity in the context of G. palustris conservation is discussed

Floral structure and pollen morphology of two zinc violets (Viola lutea ssp. calaminaria and V. lutea ssp. westfalica) indicate their taxonomic affinity to Viola lutea

Two zinc violets, the yellow form of the Aachen–Liège area and the blue morph of Blankenrode in western Westphalia, have very restricted occurrence on heavy metal waste heaps. Their taxonomic affinities have not been finally resolved. The flower micromorphological analysis presented here indicates that both zinc violets are closely related to the alpine Viola lutea, in line with our earlier published molecular data, but not with the conclusions of other authors. The zinc violets are classed at the rank of subspecies as V. lutea: ssp. calaminaria for the yellow zinc violet and ssp. westfalica for its blue counterpart. Although the violets examined (V. lutea, V. lutea ssp. calaminaria, V. lutea ssp. westfalica) are closely related, there is no evidence that V. lutea ssp. westfalica is a descendent of V. tricolor. Here we provide the most detailed information on generative organ structure in the four violets studied

Arabidopsis cyclin-dependent kinase gene Cdkg;2 is involved in organogenic responses induced in vitro

The Arabidopsis CDKG;2 gene encodes a putative cyclin-dependent Ser/Thr protein kinase of unknown biological function. This gene shows structural similarity to animal and human cyclin-dependent (PITSLRE) kinases. This study used the homozygous knockout cdkg;2 mutant based on T-DNA insertional line SALK_090262 to study the effect of mutation of the CDKG;2 gene on explant response and in vitro plant regeneration. For callus induction and proliferation, hypocotyls and cotyledons of 3-day-old seedlings of cdkg;2 and A. thaliana ecotype Col-0 were cultured on solid MS medium supplemented with 2,4-D (2 mg l-1). Organogenesis was induced after callus transfer on MS + TDZ (0.5 mg l-1). The initiation time of callus and shoot induction differed between the mutant and control cultures. Shoot regeneration after callus transfer on MS + TDZ was delayed in cdkg;2 (31 days versus 7 days in Col-0). Shoots formed on callus derived from Col-0 hypocotyls but not on cotyledon-derived callus; in cdkg;2, shoots developed on both callus types. Mutant shoots did not form roots, regenerants were dwarfed, and inflorescences had small bud-like flowers with a reduced corolla and generative organs. Abnormalities observed during cdkg;2 organogenesis suggest a role of CDKG;2 as a regulator of adventitious root initiation

Floral structure and pollen morphology are important characters in taxonomy of the genus Viola (Violaceae)

the pistil with stigma, stamen appendages (nectaries) and pollen heteromorphism are important diagnostic features in the genus ViolaL. The style characters were crucial in the very early classifications of this genus (Clausen 1927). We analyzed in details, using scanning electron microscopy (SEM), the microstructural characters of generative organs (style and stigma, stamens with nectaries) and pollen in representatives of three sections (Viola L., Melanium Ging., DischidiumGing.) occurring in Poland to get insights into the relatedness among far-related (different sections) and closely related (sub-sections within section) species. There is a great difference in stigma micromorphology between sections. In the section Violaflowers have style beaked at the apex, glabrous or covered by papillae and/or hairs, depending of subsection. Monotypic section Dischidiumwith one species V. biflora L. characterizes 2-lobed stigma. Cup-shaped stigma with the hole on the top and a lip below, covered with papillae and hairs on its outer surface occurs in pansies of the section Melanium. Pollen is highly heteromorphic (different pollen morphs, from three up to six apertures within one flower or even within one pollen sac) in the Melaniumsection and weakly heteromorphic mainly with three apertures in diploids of Viola and Dischidiumsections. This character is independent of the polyploidy in the Melaniumbut not in Violasection (Dajoz 1999). The flower micromorphological characters are also useful in reconstruction of closely related species origin. Based on stigma and nectaries features, two zinc violets are more similar to the alpineV. lutea, than to V. tricolor, indicated also as the ancestor (Kuta et al.2012)