Evidence for separate elongation enzymes for very-long-chain-fatty-acid synthesis in potato (Solanum tuberosum).

Aging potato (Solanum tuberosum) tuber discs in a Ca2+-containing medium resulted in increased rates of fatty acid labelling from [1-14C]acetate with time. Maximal labelling rates were seen after 6-8 h aging in a number of varieties. Saturated very-long-chain fatty acids (C20 and particularly C22 and C24) were very poorly labelled in freshly cut tissue. They were synthesized in increasing amounts and in a homologous sequence with progressive aging times. Use of increasing induction times and cycloheximide or puromycin as protein-synthesis inhibitors indicated that the sequence of fatty acid elongation was dependent on protein synthesis de novo and was controlled by three separate specific elongase enzymes.     

Intra-specific fusions in Solanum tuberosum

Summary Plants were regenerated from callus arising from protoplast fusion of two S. tuberosum diploids. Tetraploid progeny from the fusion of the two diploid partners had increased vigor. Isozyme analysis confirmed the presence of proteins from both partners in the fusion progeny. Pigmentation of tubers and anthers was heightened substantially in the fusion products. This fusion, the first intra-specific fusion within S. tuberosum, indicates that somatic fusion may be useful for transferring traits within this group.     

Transfer RNAs of potato (Solanum tuberosum) mitochondria have different genetic origins.

Total transfer RNAs were extracted from highly purified potato mitochondria. From quantitative measurements, the in vivo tRNA concentration in mitochondria was estimated to be in the range of 60 microM. Total potato mitochondrial tRNAs were fractionated by two-dimensional polyacrylamide gel electrophoresis. Thirty one individual tRNAs, which could read all sense codons, were identified by aminoacylation, sequencing or hybridization to specific oligonucleotides. The tRNA population that we have characterized comprises 15 typically mitochondrial, 5 'chloroplast-like' and 11 nuclear-encoded species. One tRNA(Ala), 2 tRNAs(Arg), 1 tRNA(Ile), 5 tRNAs(Leu) and 2 tRNAs(Thr) were shown to be coded for by nuclear DNA. A second, mitochondrial-encoded, tRNA(Ile) was also found. Five 'chloroplast-like' tRNAs, tRNA(Trp), tRNA(Asn), tRNA(His), tRNA(Ser)(GGA) and tRNA(Met)m, presumably transcribed from promiscuous chloroplast DNA sequences inserted in the mitochondrial genome, were identified, but, in contrast to wheat (1), potato mitochondria do not seem to contain 'chloroplast-like' tRNA(Cys) and tRNA(Phe). The two identified tRNAs(Val), as well as the tRNA(Gly), were found to be coded for by the mitochondrial genome, which again contrasts with the situation in wheat, where the mitochondrial genome apparently contains no tRNA(Val) or tRNA(Gly) gene (2).     

Changes of gene expression in Solanum tuberosum L. as a result of transgenes

Potato plants of various cultivars, transformed using Agrobacterium tumefaciens with pGV941 plasmid, differed from control plants in glyphosate herbicide tolerance, tryptophane content, intensity of callusogenesis, microtuber formation in vitro and multimolecular forms of peroxidase (EC 1.11.1.7) and superoxide dismutase (EC 1.15.1.11). The results demonstrate the influence of alien DNA on structural gene expression in transgenic plants.     

Endogenous Cytokinins in Solanum tuberosum as Influenced by Photoperiod and Temperature

Using the cucumber cotyledon bioassay, in combination with paper and column chromatographic techniques, 4 compounds exhibiting cytokinin activity were detected in extracts of Katahdin potato plant tissues. Two of these compounds were significantly higher in plants grown under inducing conditions (26°C day and 12°C night with an 8-h photoperiod) than those grown under non-inducing conditions (28°C day and 25°C night with a 16-h photoperiod). One compound increased 10-fold in above-ground tissue after only 2 Inductive cycles. Both compounds reached their maximum values in below-ground tissue after 6 days under inducing conditions, with tuber initiation observed after 8 to 10 days.     

Use of tuber progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents, chosen for their fertility, from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. The progenies were grown in randomised complete block trials with two replicates at a high-grade seed site from 1994 to 1996 inclusive and at a ware site in 1995 and 1996. The parents were included in the ware trials. Tubers were assessed for visual preference in all trials and for fry colour at both sites in 1996. Emergence and maturity were recorded in the ware trials and the tubers were assessed for yield, dry matter, size, appearance (regularity of shape), scab, uniformity, sprouting in store and keeping quality. There were very few growth cracks and very few internal defects. No reciprocal differences were found. Inbreeding depression was marked for emergence, yield, tuber size and appearance, and visual preference. In contrast, the selfs had a lighter fry colour than the parents and F₁s. Combining-ability analysis (selfs omitted) identified fry colour, emergence, maturity, yield, dry matter and sprouting resistance as traits for which the GCA (general combining ability) variance and narrow-sense heritability were high enough for good progress from full-sib family selection. Correlations between GCAs for pairs of traits were examined, including those from previously published seedling progeny tests. For fry colour, an unfavourable correlation with low yield (r = 0.596) was compensated by a favourable one with high dry matter content (r = 0.652), whereas unfavourable ones between foliage and tuber blight resistance and sprouting susceptibility (r = 0.578 and 0.596) were identified for monitoring. Clones with high GCAs were identified for use as parents in future breeding and the extent to which GCAs could be predicted from the parents, and the offspring means from the midparent means, was determined by regression and correlation analysis. The offspring-midparent regression was highest for fry colour, followed by dry matter, emergence and sprouting. Values were lower for scab due to environmental variation; for maturity, yield and tuber size due to SCA (specific combining ability); and for visual preference due to both factors. The implications for a breeding strategy are discussed. Received: 28 November 1998 / Accepted: 19 December 1998     

Use of seedling progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents chosen for their male fertility from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. Seedling progeny tests were used to evaluate the progenies for non-race-specific resistance to late blight (Phytophthora infestans) in both foliage and tubers, quantitative resistance to the white potato cystnematode (PCN) (Globodera pallida) and the commercial worth of their tubers as judged by breeders' visual preference. No reciprocal differences were found. Comparisons of the selfs and crosses revealed inbreeding depression for breeders' preference, which varied among the parents from negligible to severe, whilst there were also statistically significant differences for foliage and tuber blight, but not for PCN. When the selfs were omitted from the combining ability analyses, large differences in general combining ability (GCA) were found for all four traits, and smaller differences in specific combining ability for tuber blight and breeders' preference. The only statistically significant correlation between GCAs for different traits was a favourable one of r = 0.56 between foliage and tuber resistance to late blight. It was concluded that prospects were good for simultaneously improving all four traits by multitrait genotypic recurrent selection.     

Comparative genome analysis of Solanum lycopersicum and Solanum tuberosum

Solanum lycopersicum and Solanum tuberosum are agriculturally important crop species as they are rich sources of starch, protein, antioxidants, lycopene, beta-carotene, vitamin C, and fiber. The genomes of S. lycopersicum and S. tuberosum are currently available. However the linear strings of nucleotides that together comprise a genome sequence are of limited significance by themselves. Computational and bioinformatics approaches can be used to exploit the genomes for fundamental research for improving their varieties. The comparative genome analysis, Pfam analysis of predicted reviewed paralogous proteins was performed. It was found that S. lycopersicum proteins belong to more families, domains and clans in comparison with S. tuberosum. It was also found that mostly intergenic regions are conserved in two genomes followed by exons, intron and UTR. This can be exploited to predict regions between genomes that are similar to each other and to study the evolutionary relationship between two genomes, leading towards the development of disease resistance, stress tolerance and improved varieties of tomato.     

Structure of barogenin from Solanum tuberosum

The budding tuber of Solanum tuberosum accumulated barogenin. Its structure was determined by chemical and spectroscopic studies as (25S)-3β, 26-dihydroxy-cholest-5-ene-16,22-dione, the (25S)-epimer of kryptogenin. The biogenetic relationship between barogenin and spirostanols is discussed.     

Increased Chorismate Mutase Levels as a Response to Wounding in Solanum tuberosum L. Tubers

Discs excised from Solanum tuberosum L. cv White Rose tubers demonstrated a 4.5-fold increase in chorismate mutase activity 48 hours after excision. Incubation in the presence of cycloheximide (25 micromolar) or actinomycin D (100 micromolar) completely inhibited the wound response suggesting de novo synthesis of chorismate mutase. Ratios of activity in the presence of the activator tryptophan to that in the absence of tryptophan remained relatively constant during the induction period. This indicated either a constant ratio of tryptophan sensitive to tryptophan insensitive isozymes, or that only one form of chorismate mutase was present. Chromatography of crude extracts on three different columns yielded only one peak of chorismate mutase activity, activated by tryptophan in each case. Incubation under white light had no effect on chorismate mutase activity when compared to dark controls.     

Genomic instability in Solanum tuberosum x Solanum kurtzianum interspecific hybrids.

The use of interspecific crosses in breeding is an important strategy in improving the genetic base of the modern cultivated potato, Solanum tuberosum L. Until now, it has normally been interspecific Solanum hybrids that have been morphologically and cytologically characterized. However, little is known about the genomic changes that may occur in the hybrid nucleus owing to the combination of genomes of different origin. We have observed novel AFLP bands in Solanum tuberosum x Solanum kurtzianum diploid hybrids; 40 novel fragments were detected out of 138 AFLP fragments analyzed. No cytological abnormalities were observed in the hybrids; however, we found DNA methylation changes that could be the cause of the observed genomic instabilities. Of 277 MSAP fragments analyzed, 14% showed methylation patterns that differed between the parental species and the hybrids. We also observed frequent methylation changes in the BC1 progeny. Variation patterns among F1 and BC1 plants suggest that some methylation changes occurred at random. The changes observed may have implications for potato breeding as an additional source of variability.     

Mitochondrial DNA rearrangements in somatic hybrids of Solanum tuberosum and Solanum brevidens

Summary Thirty somatic hybrids between Solanum tuberosum and Solanum brevidens were analysed for mitochondrial and chloroplast genome rearrangements. In all cases, the chloroplast genomes were inherited from one of the parental protoplast populations. No chloroplast DNA alterations were evident but a range of mitochondrial DNA alterations, from zero to extensive intra- and inter-molecular recombinations, were found. Such recombinations involved specific recombination hot spots in the mitochondrial genome. Not all hybrids regenerated from a common callus possessed identical mitochondrial genomes, suggesting that sorting out of mitochondrial populations in the callus may have been incomplete at the plant regeneration stage. Sorting out of organelles in planta was not observed.     

马铃薯NOA基因的克隆及序列分析(英文)

以马铃薯(Solanum tuberosum)为实验材料,利用电子克隆和RACE技术,从马铃薯中克隆出NOA(nitric oxide associated factor)基因,命名为StNOA1,测序结果表明,其cDNA序列长度为1 929 bp,此片段包含一个长为1 632 bp的完整编码框.氨基酸序列比对分析表明,StNOA1与烟草(Nicotiana benthamiana),葡萄(Vitis vinifera),蓖麻(Ricinus communis),水稻(Oryza sativa),玉米(Zea mays)以及拟南芥(Arabidopsis thaliana)均有很高的同源性 (89.44%～63.56%).同AtNOA1一样,StNOA1也具有保守的GTP结合区.从结构分析结果推测,StNOA1和AtNOA1在功能上有一定的相关性,其也可能通过调节内源NO的释放参与到植物生长、发育、抗逆等过程中.     

Sugar metabolism in developing tubers of Solanum tuberosum

Regulation of the sugar content of the developing tubers of three varieties (King Edward, Maris Bard, Pentland Javelin) of Solanum tuberosum was investigated. Sucrose, glucose, fructose, UDP-glucose and fructose-2,6-bispbosphate were measured during tuber development as were the maximum catalytic activities of acid invertase, alkaline invertase, sucrose synthase, α-glucan phosphorylase, hexokinase, phospbofructokinase and pyrophosphate: fructose 6-phosphate 1-phosphotransferase [PFK(PPi)]. Sucrose was the dominant sugar and there was less fructose than glucose; the amounts of all three per gram fresh weight fell during tuber development. The activity of hexokinase per gram fresh weight declined during development but those of the other enzymes listed did not alter significantly. No change in the amounts of fructose-2,6-bisphosphate or UDP-glucose per gram fresh weight were found. The above measurements suggest that much of the sucrose translocated to the developing tuber is metabolized via sucrose syntbase to UDP-glucose that is converted to glucose 1-phosphate by UDP-glucose pyrophosphorylase using pyrophosphate generated by PFK (PPi).     

Microtuberization in potato (Solanum tuberosum L.)

Twenty-two genotypes of potato (Solanum tuberosum L.) were induced to form microtubers under six in vitro culture conditions. Cultures maintained under a short photoperiod (10 h of 6–12 μmol m^–2 s^–1) and low temperatures (day 20°±2°C and night 18°±2°C) had both a higher yield (255 mg/plantlet) and a greater number (2/plantlet) of microtubers than those maintained under long days (16 h of 38–50 μmol m^–2 s^–1) combined with high temperatures (day 28°±2°C and night 25°±2°C) (yield 207 mg/plantlet; microtuber number, 0.9/plantlet), over a wide range of genotypes. After the plantlets had been cultured under long days for an initial period of 60 days, continuous darkness advanced microtuberization by 2–3 months in various genotypes. Under short-day and low-temperature conditions the addition of 6-benzylaminopurine increased microtuber yield from 255 mg/plantlet to 645 mg/plantlet and average microtuber weight from 115 mg to 364 mg. A similar pattern was observed under conditions of long days and high temperature, and continuous darkness and low-temperature. Microtubers produced under light had a greater number of eyes (maximum average: 5.96/microtuber) than those produced in the dark (maximum average: 3.50/plantlet). The genotype × cultural conditions interactions were significant indicating the importance of developing genotype-specific protocols to maximize microtuberization. Received: 17 September 1997 / Revision received: 12 December 1997 / Accepted: 1 January 1998     

Leaf Expansion in the Potato, Solanum tuberosum

The effects of a number of manipulative treatments together with the application of the growth hormones IAA and GA on leaf expansion in the potato, variety Majestic, were investigated. It was found that removal of the apex and its surrounding non-expanded leaves resulted in an increase in both the rate and the extent of expansion of Ihe remaining upper leaves on the system. Application of IAA and GA to decapitated shoots showed that the rate of leaf expansion was decreased by IAA both alone and in combination with GA, whereas it was increased by GA treatment. Further investigations indicated that the response of a leaf to GA treatment was determined by the area and position of the leaf al the time of treatment and also by the number of expanding leaves on the system. It is postulated that this is due, at least in part, to competition for some factor or factors, which could be nutrients, within the system.     

RFLP analysis and linkage mapping in Solanum tuberosum

Summary A morphologically and agronomically heterogeneous collection of 38 diploid potato lines was analysed for restriction fragment length polymorphisms (RFLPs) with 168 potato probes, including random genomic and cDNA sequences as well as characterized potato genes of known function. The use of four cutter restriction enzymes and a fragment separation range from 250 to 2,000 bases on denaturing polyacrylamide gels allowed the detection of RFLPs of a few nucleotides. With this system, 90% of all probes tested showed useful polymorphism, and 95% of those were polymorphic with two or all three enzymes used. On the average, 80% of the probes were informative in all pairwise comparisons of the 38 lines with a minimum of 49% and a maximum of 95%. The percentage of heterozygosity was determined relative to each other for each line and indicated that direct segregation analysis in F1 populations should be feasible for most combinations. From a backcross involving one pair of the 38 lines, a RFLP linkage map with 141 loci was constructed, covering 690 cMorgan of the Solanum tuberosum genome.