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     

Cotransformation and differential expression of introduced genes into potato (Solanum tuberosum L.) cv Bintje

Summary The Dutch potato cultivar Bintje has been transformed by Agrobacterium strain LBA1060KG, which contains two plasmids carrying three different DNAs (TL- and TR-DNA on the Agrobacterium rhizogenes plasmid and TKG-DNA on the pBI121 plasmid). Several transformed root clones were obtained after transformation of leaf, stem, and tuber segments, and plants were then regenerated from these root clones. The expression of the various marker genes [rol, opine, -glucuronidase (GUS), and neomycin phosphotransferase (NPTII)] was determined in several root clones and in regenerated plants. The selection of vigorously growing root clones was as efficient as selection for kanamycin resistance. In spite of the location of NPTII and GUS genes on the same T-DNA, 17% of the root clones did not show GUS activity. Nevertheless, Southern blot analysis showed that these root clones contained at least three copies of the GUS gene. Sixty-four per cent of the root clones contained opines. The expression of these genes, however, was negatively correlated with plant regeneration capacity and normal plant development. The differential expression of the marker genes in the transgenic potato tissues is discussed.     

cDNA cloning and expression of a potato (Solanum tuberosum) invertase

A cDNA clone encoding an invertase isoenzyme has been isolated from a potato leaf cDNA library. The deduced amino acid sequence shows significant similarities to previously characterised invertases. The highest degree of overall similarity, including the signal peptide sequence, is to carrot cell wall invertase, suggesting that the potato gene encodes an apoplastic enzyme. Expression of the gene, as determined by RT-PCR, is detected in stem and leaf tissue, and at lower levels in tuber, but is absent from roots.     

Protein profiling in potato (Solanum tuberosum L.) leaf tissues by differential centrifugation

Foliar diseases, such as late blight, result in serious threats to potato production. As such, potato leaf tissue becomes an important substrate to study biological processes, such as plant defense responses to infection. Nonetheless, the potato leaf proteome remains poorly characterized. Here, we report protein profiling of potato leaf tissues using a modified differential centrifugation approach to separate the leaf tissues into cell wall and cytoplasmic fractions. This method helps to increase the number of identified proteins, including targeted putative cell wall proteins. The method allowed for the identification of 1484 nonredundant potato leaf proteins, of which 364 and 447 were reproducibly identified proteins in the cell wall and cytoplasmic fractions, respectively. Reproducibly identified proteins corresponded to over 70% of proteins identified in each replicate. A diverse range of proteins was identified based on their theoretical pI values, molecular masses, functional classification, and biological processes. Such a protein extraction method is effective for the establishment of a highly qualified proteome profile.     

Chloroplast DNA evolution in potato (Solanum tuberosum L.)

Summary A deletion specific to chloroplast (ct) DNA of potato (Solanum tuberosum ssp. tuberosum) was determined by comparative sequence analysis. The deletion was 241 bp in size, and was not flanked by direct repeats. Five small, open reading frames were found in the corresponding regions of ctDNAs from wild potato (S. tuberosum ssp. andigena) and tomato (Lycopersicon esculentum). Comparison of the sequences of 1.35-kbp HaeIII ctDNA fragments from potato, tomato, and tobacco (Nicotiana tabacum) revealed the following: the locations of the 5 ends of both rubisco large subunit (rbcL) and ATPase beta subunit (atp) mRNAs were probably the same as those of spinach (Spinacia oleracea); the promoter regions of the two genes were highly conserved among the four species; and the 5 untranslated regions diverged at high rates. A phylogenetic tree for the three potato cultivars, one tomato cultivar, and one tobacco cultivar has been constructed by the maximum parsimony method from DNA sequence data, demonstrating that the rate of nucleotide substitution in potato ctDNA is much slower than that in tomato ctDNA. This fact might be due to the differences in the method of propagation between the two crops.     

In vitro microtuberization in potato (Solanum tuberosum L.) cultivars

Mechanism of microtuberization in three elite cultivars kufri badhsha (KB), kufri chandramukhi (KCM) and kufri jawahar (KJ) of potato was studied. Sprouts of all the three cultivars were used to obtain in vitro shoot cultures. MS medium supplemented with chlorocholine chloride was found to be most suitable for all the cultivars. Maximum tuberization was obtained under incubation conditions of continuous darkness at 20 degrees +/- 1 degrees C. The highest number of micro-tubers per plant basis was produced under continuous darkness and KCM recorded the highest yield of micro-tubers and was found significantly superior to KJ and KB.     

Pectolytic enzymes produced byRhizoctonia bataticola in culture andRhizoctonia-infected tissues of potato tubers (Solanum tuberosum L.)

Rhizoctonia bataticola produced both polygalcturonase (PG) and pectin-methyl-esterase (PME) in vitro and in vivo, the former releasing more reducing materials in reaction mixtures. Extracts of healthy tissues ofSolanum tuberosum contained PME but no PG. Salt extraction of healthy and diseased tissues increased the amount of PME obtained. The activity of PME produced in vivo increased after dialysis and addition of salt to reaction mixtures whereas the PME produced in vitro was neither affected by dialysis nor influenced by addition of salt to the preparations. Enzyme filtrates from culture andRhizoctonia-infected tissues induced rot symptoms onto sterilized pealed healthy tubers ofS. tuberosum whereas the extracts from healthy tissues did not.     

Cold-induced sweetening development in Indian potato (Solanum tuberosum L.) varieties

Developing cold sweetening resistant processing varieties is one of the frontal areas of research all over the world. In India, first potato processing variety was released in the year 1998 and till 2005 three varieties have been developed. But, there is no information available regarding sugar accumulation response of Indian varieties to low temperature storage. Therefore, it is imperative to generate basic information on cold sweetening development in Indian processing varieties for the use of potato breeders. Development of cold-induced sweetening and its relation to phenolic content of the tuber was studied in three Indian potato varieties viz., Kufri Chipsona-1, Kufri Chipsona-3 and Kufri Jyoti. The reducing sugars decreased in initial phase of storage, followed by continuous increase to unacceptably higher levels after around two weeks of storage. The increase in reducing sugar contents took place subsequent to increase in sucrose content. The changes in phenol content were not in a fixed trend. The degree or number of folds increase in reducing sugar content was relatively less in Kufri Jyoti which contained highest phenol content among the three varieties investigated. It is suggested that development of processing varieties with higher anti-oxidant content and lower invertase activity may provide better cold-induced sweetening resistance.     

Carbon isotope discrimination in irrigated and droughted potato (Solanum tuberosum L.)

Carbon isotope discrimination (Δ) was measured in irrigated and droughted potato. Under irrigation, Δ in leaflets at given nodes increased (P < 0.001) between 21 and 63 d after emergence (DAE), which was attributed to increasing stomatal conductance (g_s) during leaf expansion. The effect of leaf position on Δ was non-significant in mature leaves. Under drought, Δ decreased (P < 0.001) in successive leaves up the stem, reflecting changes in g_s and water stress. At each node Δ remained constant or decreased, suggesting that effects of water stress were greater than changes with leaf expansion. There were significant differences in Δ between cultivars in both treatments, and in the progressive decrease in Δ up the stem under drought. Differences in Δ between cultivars were consistent with differences in stomatal control of leaf water status following water stress. Values for Δ in tubers were consistently lower than in stem and leaf, and decreased more rapidly. Differences in Δ between cultivars did not reflect dry matter production in either treatment, and differences in water use were non-significant between cultivars under drought. So, plants can achieve similar dry matter production through different growth strategies when irrigated or droughted, and Δ does not provide a simple, indirect method of selecting for dry matter production under water stress.     

Expression of bacterial cellulase genes in transgenic alfalfa (Medicago sativa L.), potato (Solanum tuberosum L.) and tobacco (Nicotiana tabacum L.)

The genes encoding thermostable cellulases E2 and E3 of Thermomonospora fusca were expressed in plants under the control of the constitutive, hybrid Mac promoter. For both E2 and E3, the genes were modified so as to remove the sequence encoding the bacterial leader peptide. Western blot analysis indicated that expression levels of recombinant cellulase in tobacco lines ranged up to about 0.1% (E2) and 0.02% of soluble protein (E3). No phenotypic effect of cellulase expression was noted. Recombinant E2 expressed in either tobacco or alfalfa was active and retained heat stability. These findings are an important first step in the development of crop plants as a production system for cellulases.     

Interspecific somatic hybrids between wild potato Solanum acaule Bitt. and anther-derived dihaploid potato (Solanum tuberosum L.)

Solanum acaule Bitt. is a disomic tetraploid (4x) wild potato species which is resistant to several potato diseases. Introgression of disease resistance and abiotic stress tolerance to the tetrasomic tetraploid (4x) cultivated potato (S. tuberosum L.) gene pool via crossing has been limited due to the difference in the endosperm balance number. In the present study, protoplast fusion was applied to produce hexaploid (6x) somatic hybrids between the parental lines, tetraploid (4x) S. acaule and two anther-derived dihaploid (2x) lines of S. tuberosum cv. White Lady. One callus (0.4%) of a total of 229 calli obtained regenerated into shoots in the fusion combination S. acaule (+) White Lady 15.dh.8.2.2. All the regenerated shoots were confirmed to be interspecific somatic hybrids using species-specific RAPD markers. In another fusion combination, S. acaule (+) White Lady 7.dh.23.1.1, fifteen calli (5%) regenerated into a total of sixteen shoots from 289 calli. All the analysed somatic hybrids between S. acaule and S. tuberosum were hexaploid. The mean DNA content (2C value) of the combination S. acaule (+) White Lady 15.dh.8.2.2 somatic hybrids (4.55 pg), was approximately the sum (4.69 pg) of the DNA contents of the parental lines, S. acaule (2.95 pg) and S. tuberosum (1.74 pg). In the greenhouse, the two somatic hybrids analysed were normal in their morphological characteristics and more vigorous than their parental lines. Most of the morphological characteristics were closer to the tetraploid S. acaule than to the dihaploid S. tuberosum. The interspecific somatic hybrids are currently being tested for frost tolerance and glycoalkaloid composition. Received: 19 January 1998 / Revision received: 27 March 1998 / Accepted: 20 April 1998     

Differentiation of potato (Solanum tuberosum L.) plants from cultured leaf protoplasts

Through induction of totipotent stage in cultured cells plants were regenerated from protoplast derived callus colonies of potato. Growing of the plants in vitro with optimal aeration and pretreatment of the leaves in dark and cold prior to protoplast isolation has improved the protoplast yield and frequency of cell division. Protoplasts of four potato genotypes have started to divide within 2-5 days after plating them into culture medium containing 2,4-D (0.2 mg/l); ZEA (0.5 mg/l); and NAA (1 mg/l) as growth regulators. Embedding of the cells into agarose proved to be favourable to avoid cell browning and to increase colony formation. The series of hormone treatments based on complex action of NAA and BAP promoting colony growth and greening, ZEA and IAA inducing shoot redifferentiation, and GA3 plus NAA supporting shoot elongation and rooting, finally resulted in high frequency of plant regeneration from microcolonies.     

Induction of alcohol dehydrogenase in explants of potato tuber (Solanum tuberosum L.)

Plant Cell Reports - During callus formation a huge increase in alcoholdehydrogenase activity was observed in potato tuber tissue discs. Callus formation was no prerequisite for this increase;...     

Effect of photoperiod on in vitro tuberization of potato (Solanum tuberosum L.)

Single-node cuttings of potato cultivars Jemseg, Katahdin, Russet Burbank and Superior were cultured on a multiplication medium containing MS salts and no growth regulators. Cultures were exposed to 8 h (SD) and 16 h (LD) photoperiodic regimes. The subsequent plantlets were excised and single node cuttings from each photoperiodic regime were placed under SD or LD on a second medium containing growth regulators which promoted tuberization. Production of microtubers was strongly influenced by genotype and by photoperiodic treatments. Superior produced stunted plantlets and some microtubers under SD conditions in the multiplication medium. The number of microtubers formed by Jemseg was not influenced by photoperiod. However, Katahdin and Russet Burbank formed fewer microtubers under LD-LD conditions compared to LD-SD, SD-SD and SD-LD regimes. Compared with the other regimes, LD-SD photoperiod generally promoted microtuber formation with larger diameters and significantly (p<0.05) greater fresh weight. The intensity of the tuberization stimulus was affected by daylength, and this was characterized by microtubers with secondary tubers, the growth of more than one axillary microtuber, and microtubers subtended by stolons. The maturity group of the potato cultivars and photoperiodic regime in vitro strongly influenced the production of microtubers. These results can be employed to adapt light regimes for multiplication and tuberization to the specific requirements for cultivars from different maturity groups, and thus increase the efficiency of potato multiplication protocols.     

Metabolite profiling of potato (Solanum tuberosum L.) tubers during wound-induced suberization

Suberin is a specific cell wall-associated biopolymer characterized by the deposition of both a poly(phenolic) domain (SPPD) associated with the cell wall, and a poly(aliphatic) domain (SPAD) thought to be deposited between the cell wall and plasma membrane. In planta, suberin functions to prevent plants from desiccation and pathogen attack. Although the chemical identity of the monomeric components of the SPPD and SPAD are well known, their concerted biosynthesis and assembly into the suberin macromolecule is poorly understood. To expand our knowledge of suberin biosynthesis, a GC/MS-based metabolite profiling study was conducted, using wound healing potato (Solanum tuberosum L.) tubers as a model system. A time series of both non-polar and polar metabolite profiles were created, yielding a broad-based, dynamic picture of wound-induced metabolism, including suberization. Principal component analysis revealed a separation of metabolite profiles according to different suberization stages, with clear temporal differences emerging in the non-polar and polar profiles. In the non-polar profiles, suberin-associated aliphatics contributed the most to cluster formation, while a broader range of metabolites (including organic acids, sugars, amino acids and phenylpropanoids) influenced cluster formation amongst polar profiles. Pair-wise correlation analysis revealed strong correlations between known suberin-associated compounds, as well as between suberin-associated compounds and several un-identified metabolites in the profiles. These data may help to identify additional, as yet unknown metabolites associated with suberization process.     

Protein kinase activity in different stages of potato (Solanum tuberosum L.) microtuberization

In vitro culture was used to study morphogenetic aspects of the tuberization process under controlled conditions in potato (Solanum tuberosum L.) plants. This paper accurately defines four stages of tuber development and their correlation to external morphological characteristics and histological structures. Protein kinase activity, assayed in each stage using Historic HAS as substrate, was differentially expressed during the tuberization process. Phosphorylation was maximum in the first stages of tuber formation. The incorporation of [³²PO₄ ^–1] to endogenous peptides containing serine/threonine amino acidic residues followed the same pattern that the protein kinase activity did.Abbreviations EDTA Ethylenediaminetetraacetic acid - EGTA ethylenebis (oxyethylenenitrilo) tetraacetic acid - MOPS 4-morpholine-propanesulfonic acid     

Comparative proteomic analysis of cold-induced sweetening in potato (Solanum tuberosum L.) tuber

Cold-induced sweetening is one of the major factors limiting the quality of fried potato products. To understand the mechanisms of protein regulation for cold-induced sweetening in potato tubers, a comparative proteomic approach was used to analyse the differentially expressed proteins both during control (25 °C, 30 days) and cold treatment (4 °C, 30 days) using two-dimensional gel electrophoresis. Quantitative image analyses indicated that there were 25 protein spots with their intensities significantly altered more than twofold. Of these proteins, 9 were up-regulated, 13 were down-regulated, 2 were absent, and 1 was induced in the cold-stored tubers. The MALDI-TOF/TOF MS analyses led to the identification of differentially expressed proteins that are involved in several processes and might work cooperatively to maintain metabolic homeostasis in tubers during low-temperature storage. The preponderance of metabolic proteins reflects the inhibition of starch re-synthesis and the accumulation of sugars in carbon fluxes, linking starch–sugar conversion. The respiration-related proteins suggest the transfer of respiratory activity from aerobic respiration to anaerobic respiration in the cold-stored tubers. The proteins associated with defence appear to protect the tuber cells from low-temperature stress. Some heat shock proteins that act as chaperones also displayed a differential expression pattern, suggesting a potentially important role in cold-stored tubers, although their exact contribution remains to be investigated. The proposed hypothetical model might explain the interaction of these differentially expressed proteins that are associated with cold-induced sweetening in tubers.     

Inheritance of three electrophoretically determined protein bands in potato (Solanum tuberosum L.)

Summary A modified polyacrylamide gel electrophoresis technique is employed to resolve proteins for use as biochemical gene markers in potato. Dominant, duplicate dominant and complementary gene action are three modes of inheritance that adequately explain the segregation of three respective protein bands in two generations of crossing within diploid Phureja X haploid Tuberosum families.Scientific Journal Seires Article 10,171 of the Minnesota Agricultural Experiment Station