Cucumber: a model angiosperm for mitochondrial transformation

Abstract. Plants possess three major genomes, carried in the chloroplast, mitochondrion, and nucleus. The chloroplast genomes of higher plants tend to be of similar sizes and structure. In contrast both the nuclear and mitochondrial genomes show great size differences, even among closely related species. The largest plant mitochondrial genomes exist in the genus Cucumis at 1500 to 2300 kilobases, over 100 times the sizes of the yeast or human mitochondrial genomes. Biochemical and molecular analyses have established that the huge Cucumis mitochondrial genomes are due to extensive duplication of short repetitive DNA motifs. The organellar genomes of almost all organisms are maternally transmitted and few methods exist to manipulate these important genomes. Although chloroplast transformation has been achieved, no routine method exists to transform the mitochondrial genome of higher plants. A mitochondrial-transformation system for a higher plant would allow geneticists to use reverse genetics to study mitochondrial gene expression and to establish the efficacy of engineered mitochondrial genes for the genetic improvement of the mitochondrial genome. Cucumber possesses three unique attributes that make it a potential model system for mitochondrial transformation of a higher plant. Firstly, its mitochondria show paternal transmission. Secondly, microspores possess relatively few, huge mitochondria. Finally, there exists in cucumber unique mitochondrial mutations conditioning strongly mosaic (msc) phenotypes. The msc phenotypes appear after regeneration of plants from cell culture and sort with specific rearranged and deleted regions in the mitochondrial genome. These mitochondrial deletions may be a useful genetic tool to develop selectable markers for mitochondrial transformation of higher plants

The Genome Sequence of the North-European Cucumber (Cucumis sativus L.) Unravels Evolutionary Adaptation Mechanisms in Plants

Cucumber (Cucumis sativus L.), a widely cultivated crop, has originated from Eastern Himalayas and secondary domestication regions includes highly divergent climate conditions e.g. temperate and subtropical. We wanted to uncover adaptive genome differences between the cucumber cultivars and what sort of evolutionary molecular mechanisms regulate genetic adaptation of plants to different ecosystems and organism biodiversity. Here we present the draft genome sequence of the Cucumis sativus genome of the North-European Borszczagowski cultivar (line B10) and comparative genomics studies with the known genomes of: C. sativus (Chinese cultivar – Chinese Long (line 9930)), Arabidopsis thaliana, Populus trichocarpa and Oryza sativa. Cucumber genomes show extensive chromosomal rearrangements, distinct differences in quantity of the particular genes (e.g. involved in photosynthesis, respiration, sugar metabolism, chlorophyll degradation, regulation of gene expression, photooxidative stress tolerance, higher non-optimal temperatures tolerance and ammonium ion assimilation) as well as in distributions of abscisic acid-, dehydration- and ethylene-responsive cis-regulatory elements (CREs) in promoters of orthologous group of genes, which lead to the specific adaptation features. Abscisic acid treatment of non-acclimated Arabidopsis and C. sativus seedlings induced moderate freezing tolerance in Arabidopsis but not in C. sativus. This experiment together with analysis of abscisic acid-specific CRE distributions give a clue why C. sativus is much more susceptible to moderate freezing stresses than A. thaliana. Comparative analysis of all the five genomes showed that, each species and/or cultivars has a specific profile of CRE content in promoters of orthologous genes. Our results constitute the substantial and original resource for the basic and applied research on environmental adaptations of plants, which could facilitate creation of new crops with improved growth and yield in divergent conditions

In vitro culture of Cucumis sativus L. VI. Histological analysis of leaf explants cultured on media with 2, 4-D or 2, 4, 5-T

The developmental sequence of callus initiation and somatic embryogenesis in leaf explants of Cucumis sativus cv. Borszczagowski was analysed and compared on media containing two different auxin phenoxy-derivatives (2,4-D and 2,4,5-T) and cytokinin (BAP or 2iP). During the first 20 days of culture on media with 2,4,5-T proliferation of parenchymatic tissue occurred mainly and only small meristematic centers were observed. There was an intensive detachment of parenchymatic cells and dissociation of their cell walls near vessels and in the lower part of the explant adjacent to the medium. These cells were strongly plasmolysed. On the 2,4-D containing medium mostly meristematic tissue developed, proliferating around vascular bundles and forming meristematic centers or promeristem-like structures. After 35-50 days of culture, secondary callus was formed by separation of meristematic cells from the meristem surface in explants cultured on the 2,4-D containing medium. On medium supplemented with 2, 4, 5-T the detachment of parenchymatic and meristematic cells occurred, along with formation of a gel-like substance. The gel-like callus contained multi-cellular aggregates, proembryoids and embryoids. This type of callus tissue was initiated more intensively on medium with 2, 4, 5-T, but the frequency of somatic embryogenesis was much lower. The periferial cells of aggregates, proembryoids and embryoids showed the tendency to separate from the surface of the tissue. Many embryoids formed adventitious embryos

Plant regeneration of wild Cucumis species

Plant regeneration from C. anyuria var. longipes A. Meeuse and C. metuliferus Naud. leaf explants was investigated. It was found that embryoid-like structures were formed from C. anguria leaf explants cultured on media containing 0.3 mg dm-3 2,4-D and 0.8 mg dm-3 2iP. After being transferred to medium with 0.3 mg dm-3 2iP and 1 mg dm-3 GA3 they developed 187±49 shoots per explant. Further growth and root formation proceeded on hormone free medium

Genome sequencing makes a significant progress in plant breednig

Sekwencjonowanie genomów jest odczytaniem zapisu genetycznego, jakim dany organizm dysponuje, wyrażonego w odpowiednim uporządkowaniu nukleotydów. W efekcie uzyskujemy informację rzeczywistą o strukturze i położeniu genów i innych składników genomu, co daje podstawy do szczegółowego prognozowania cech organizmu i pozwala wyjaśniać mechanizmy wielu reakcji. Z tych powodów efekty sekwencjonowania mają wielorakie implikacje, między innymi oddziałują na nauki rolnicze w szczególności na postęp hodowlany. W artykule przedstawione zostały uwarunkowania ogólne sekwencjonowania i przybliżono znaczenie niektórych danych jakie uzyskano u ogórka.Genome sequencing is the reading of the genetic record of a given organism, expressed in the correct sequence of nucleotides. In effect, information about the real structure, location of genes and other elements of a genome is obtained. It gives a solid base for detailed prediction of the organism's traits and allows explain the mechanisms of many metabolic reaction. This is why the sequencing has many implications, for example on agricultural science, especially in breeding programs. This article presents general sequencing strategies and gives a closer look at the meaning of experimental data obtained by cucumber