Review Article: Molecular Mechanisms of Resistance to Potato virus X and Y in Potato

The most important viral pathogens of the cultivated potato are Potato virus X (PVX) and Potato virus Y (PVY), which can reduce potato production up to 80%. Thus resistance breeding is one of the major goals of plant breeders. Wild potato species are good sources of resistance (R) genes. The resistant plants respond to viral infection with hypersensitive reaction (HR) or extreme resistance (ER). HR is accompanied by programmed cell death, while ER localizes the virus at the primary infection site and limits virus replication without visible symptoms. While HR is generally strain-specific, ER can act against a broad spectrum of viral pathogens. This review aims to describe the molecular mechanisms of resistance against PVX and PVY in potato

Isolation and sequence analysis of a cDNA and a related gene for cytochrome P450 proteins from Solanum chacoense

Inosine-containing degenerate PCR primers corresponding to the heme-binding domain of cytochrome P450 proteins have been synthesized and used for cloning cDNAs by the RT-PCR technique from Solanum chacoense. One clone in which the primer was immediately followed by sequences corresponding to the remaining part of the conserved domain was obtained. A leaf cDNA and a genomic library were constructed from S. chacoense. Clones homologous to the PCR fragment were isolated by plaque hybridization from both libraries (CYPs.ch-1 and CYPs.ch-2, respectively). Based on DNA sequence analysis, the selected clones are 87.6% identical and belong to the CYP71 family. The CYPs.ch genes are present in multiple copies in the S. chacoense as well as in the S. tuberosum genome with some polymorphisms. The CYPs.ch transcripts are slightly induced by methyl jasmonate and abscisic acid in S. chacoense foliage

Potato protein kinase StCPK1: A putative evolutionary link between CDPKs and CRKs

Calcium-dependent protein kinases (CDPKs) in plants are characterized by a four-domain structure including conserved sequences in the catalytic domain, and in the C-terminal calmodulin-like domain. Based on this conservation we have PCR-amplified and isolated a potato cDNA clone (StCPK1) from a library representing an early stage of tuber development. DNA sequence analysis revealed that in the catalytic domain, StCPK1 shares more homology with CDPK-related kinases than with CDPKs; however, like CDPKs, it possesses canonical EF-hands at the calmodulin-like 3' end. StCPK1 exists in a few copies in the potato genome and is abundantly expressed in the sepals of mature flowers. Floral expression of genes homologous to StCPK1 appears to be widespread in the family Solanaceae

Isolation and characterization of a water-stress-inducible cDNA clone from Solanum chacoense

A rich source of valuable genes are wild species. Solanum chacoense Bitter with its extreme resistance to viruses, insects and drought, is a good example. In the present study, a stress gene, designated DS2, has been isolated from S. chacoense. We have shown that the expression of the gene is organ-specific being detected in leaf, stem and stolon, but not in root, tuber or flower. Treatment of detached leaves with abscisic acid (ABA), salicylic acid or methyl jasmonate resulted in only very moderate accumulation of DS2 mRNA. Thus, DS2 represents a very rare type of the water-stress-inducible genes whose signalling pathway is not primarily related to ABA. Based on DNA sequence analysis, DS2 encodes a putative protein starting with 20 amino acids homologous to the ABA- and water-stress-inducible, ripening-related (ASR) proteins of tomato continued by an insert of 155 amino acids structurally similar to certain LEAs (late embryogenesis-abundant proteins) and ending in 88 amino acids homologous again to the ASR sequences and to an unpublished partial cDNA fragment isolated from the root of rice. The N-terminal region of the DS2 protein is hydrophilic with ten 13-mer amino acid motifs and random coil structure. In contrast, the C-terminus predicts an α-helix and possesses a bipartite nuclear targeting sequence motif. These data suggest that the function of the DS2 may be the protection of the nuclear DNA from desiccation. © 1995 Kluwer Academic Publishers

Molecular markers associated with leptinine production are located on chromosome 1 in Solanum chacoense

Leptines of Solanum chacoense are effective natural deterrents against the Colorado potato beetle. Leptines are the acetylated forms of the glycoalkaloids solanine and chaconine and are supposed to be synthesised via hydroxylated derivatives, called leptinines. Inheritance of leptinine production was studied in crosses of closely related S. chacoense genotypes. The segregation data supported a single-gene model for the inheritance of leptinine production. In the segregating F1 population of a S. chacoense cross, AFLP, RFLP and RAPD markers segregating with the leptinine production have been identified. The locus involved in leptinine synthesis was localised to the short arm of chromosome 1 of the potato where a major QTL for solanidine production, and markers with tight linkage to leptine production, have been mapped before. Our data further support the previous finding that the short arm of chromosome 1 is involved in steroid alkaloid synthesis in potato, and suggest that the genes involved in leptinine and leptine production are tightly linked in S. chacoense

Chemically induced carcinogenesis affecting chromatin structure in rat hepatocarcinoma cells

A new, chemically induced animal tumor cell line (HeDe) was established and characterized by its property of causing aggressively growing tumors in specific strain of rats and changes in the chromatin structure. Results show that (1) the nuclear material in nuclei of normal resting (G0) hepatocytes consists mainly of decondensed veil-like chromatin, chromosomes being clustered in six lobular domains; (2) nuclei of HeDe cells contain primarily supercoiled chromatin; or (3) the nuclear material of tumor cells undergoes apoptosis seen as apoptotic bodies. Heterogeneity of chromatin structures was expressed as contour/area ratio and was nine times higher in apoptotic cells and two times higher in tumor cells compared to resting cell