Volume 2 Special Issue 1 2008
2008: International Year of the Potato
How to reference: Vinterhalter D, Zdravković-Korać S, Mitić N, Dragićević I, Cingel A, Raspor M, Ninković S (2008) Protocols for Agrobacterium-mediated Transformation of Potato. In: Benkeblia N, Tennant P (Eds) Potato I. Fruit, Vegetable and Cereal Science and Biotechnology 2 (Special Issue 1), 1-15
Noureddine Benkeblia, Paula Tennant
University of the West Indies, Jamaica
CONTENTS AND ABSTRACTS
Dragan Vinterhalter, Snežana Zdravković-Korać, Nevena Mitić, Ivana Dragićević, Aleksandar Cingel, Martin Raspor, Slavica Ninković (Serbia) Protocols for Agrobacterium-mediated Transformation of Potato (pp 1-15)
Invited Review: This review presents a collection of 27 studies dedicated to Agrobacterium-mediated transformation of potato. Studies were selected in order to present the gradual improvement of transformation techniques from early research to routine techniques used in many laboratories in everyday work. Some of the protocols were selected on the basis of their popularity and application in certain lines of transgene research. Apart from the more widely used A. tumefaciens there are protocols adjusted for A. rhizogenes-mediated transformation. Protocols for different explant types (shoots, leaves, tubers) are represented just as those elaborated specifically for the most important commercial cultivars like ‘Désirée’, ‘Bintje’, ‘Shepody’, ‘Kennebec’ and ‘Russet Burbank’. Emphasis in each protocol is placed on the growth response of explants exposed to various plant growth regulators and other substances and conditions which support shoot regeneration. Attention was also paid to protocols and treatments which may suppress the regeneration of aberrant, off-type plants.
Dragan Vinterhalter, Ivana Dragićević, Branka Vinterhalter (Serbia) Potato in Vitro Culture Techniques and Biotechnology (pp 16-45)
Invited Review: This review was prepared as a survey of key articles presenting development, achievements and interconnection of various lines of potato biotechnology research united through the common use of in vitro culture techniques. Starting with the early research on the induction and differentiation of callus tissues, review sequentially and chronologically presents the advance of various in vitro culture techniques and their practical applications in clonal propagation, germplasm storage, production of healthy virus-free plants and breeding. Main topics (sections) presented include: establishment and maintenance of callus, root and shoot cultures; variability in callus tissue and protoplast cultures; shoot differentiation and regeneration from various explant types and cultures, somatic embryogenesis and androgenesis; shoot and meristem tip cultures and their numerous applications; regulation of in vitro tuberization, microtubers dormancy and sprouting and systems for production of micro and minitubers. Finally, review outlines the gradual technique merging and shifting of research interest from cellular to molecular biology. This approach enables us to comprehend developmental processes in cells and tissues not only through the interaction of plant growth regulators and environmental factors but also through sequential activation and expression of regulatory genes.
Biao Wang, Zhenfang Yin, Chaohong Feng, Xiao Shi, Yupeng Li, Qiaochun Wang (China) Cryopreservation of Potato Shoot Tips (pp 46-53)
Invited Mini-Review: Potato is one of the most important staple crops in both developed and developing countries of the world. Potato genetic resources are a prerequisite for potato breeding in both conventional and genetic engineering programmes. Cryopreservation has long been considered an ideal means for the long-term conservation of plant genetic resources. This review provides comprehensive information on variously novel cryogenic techniques that have been developed since 1990. Factors affecting the success of cryopreservation of potato shoot tips are analyzed and discussed. Evidence of morphological and molecular analysis demonstrates that plants regenerated from cryopreserved shoot tips are genetically stable. Efficient elimination of potato viruses by cryotherapy of shoot tips provides an alternative method for virus elimination. Thus, the materials can be simultaneously prepared for virus elimination and long-term preservation. Routine application of cryopreservation of shoot tips for the long-term preservation of potato genetic resources has already started in Germany, Peru, Czech Republic and Korea. Species- and cultivar-specificity has to be taken into account for much wider application when cryo-protocols are to be developed. Fundamental studies on mechanisms by which potato shoot tips withstand freezing in liquid nitrogen would help solve this problem.
Noureddine Benkeblia (Jamaica), Alexios A. Alexopoulos, Harold C. Passam (Greece) Physiological and Biochemical Regulation of Dormancy and Sprouting in Potato Tuber (Solanum tuberosum L.) (pp 54-68)
Invited Review: At harvest, potato (Solanum tuberosum L.) tubers are in a dormant state and do not have the ability to sprout. After harvesting, tuber dormancy is released progressively. This release is accompanied by numerous physiological and biochemical changes, such as carbohydrate hydrolysis and the accumulation of saccharides, which are detrimental to the nutritional and processing qualities of potatoes. Endogenous hormones are thought to play a significant role in the regulation of tuber dormancy and in the onset of sprouting. This review aims to describe the involvement of all major classes of endogenous hormones in tuber dormancy, as well as the physiological and biochemical changes during these steps. Based on current scientific evidence, both abscisic acid (ABA) and ethylene are required for the induction of dormancy, however, only ABA plays a role in maintaining bud dormancy. Moreover, an increase in cytokinin sensitivity and content appear to be the principal factor leading to the release of dormancy. Changes in endogenous indole-3-acetic acid (IAA) and gibberellin (GA) content appear to be more closely related to the regulation of subsequent sprout growth. Physiological and biochemical changes during tuber dormancy and the termination of dormancy centre on carbohydrate levels and the activity of enzymes involved in carbohydrate metabolism. In particular, starch breakdown, accompanied by an increase in the concentration of sucrose and reducing sugars, appears to play an important role in the onset of sprouting of tuber buds. Many of these changes are initially observed in tissues in the region of the buds, but subsequent growth of the sprout significantly affects the metabolism of tissues in other regions of the tuber. The application of dormancy-breaking chemicals, such as bromoethane, or phytohormones (GA3), to potato tubers induces metabolic changes that lead to dormancy breakage. These changes differ between treatments and also from those occurring when dormancy is broken naturally.
Kyong-Hee Nam, Teruhiko Yoshihara (Japan) Bioorganic Chemistry of the Induction of Potato Tuber Formation: A Review (pp 69-81)
Invited Review: In the potato (Solanum tuberosum), tuberization is a complex developmental process, leading to the formation of a specialized storage organ by the differentiation of the underground stolon. Tuberization begins with the perception of environmental signals in the leaves. Under short day (SD) conditions and cool temperatures, potato plants produce tubers, while they remain in a vegetative stage under long day (LD) conditions or high temperatures. Environmental signals exercise influences on the control of potato tuberization via several plant hormones and other endogenous factors. Tuberonic acid glucoside (TAG) isolated from the leaves of potato plants is the proposed as specific tuber-inducing substance. Tuberonic acid (TA) and jasmonic acid (JA), which are closely related compounds to TAG, have also showed strong activities on tuber induction. The generation of TAG is associated with the linolenic acid (LA) cascade. In the LA cascade, JA is biosynthesized from 13(S)-hydroperoxylinolenic acid (HPOT), catalyzed by lipoxygenase (LOX) as an initial enzyme, and then JA is metabolized to TA and finally converted into TAG. In the present review, which is aimed at elucidating the mechanism of potato tuber induction by means of temperature and LOX derivatives, low temperature was favorable for tuber induction of potato, and LOX activity appeared high level at the initial stage of potato tuberization and was stimulated by low growing temperature. In addition, the high endogenous levels of JA, TA, and TAG were observed at low temperature suggesting that the increase in LOX, which is activated by low temperature, results in large amounts of endogenous JA, TA and TAG, which play a crucial role in potato tuber induction. On the other hand, inhibitory effect for tuber induction under unfavorable environmental conditions could be recovered partially by the treatment of theobroxide, an exogenous tuber-inducing compound.
Judit Dobránszki, Katalin Magyar-Tábori, Ildikó Hudák (Hungary) In Vitro Tuberization in Hormone-Free Systems on Solidified Medium and Dormancy of Potato Microtubers (pp 82-94)
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Invited Review: The use of in vitro tubers (microtubers) as the final products of potato micropropagation, in addition to or rather than in vitro plantlets has several advantages in seed tuber production. Moreover, microtubers are important in germplasm storage and they are used as experimental tools in basic research and in in vitro selection of agronomically important characters. Their reliable production has, therefore, been widely studied under different in vitro growing conditions, with varying efficacy regarding the number, size and weight of microtubers. Microtubers exhibit different periods of dormancy depending on the genotype and on the in vitro conditions during tuberization. Generally, the use of growth regulators for tuberization does not allow the maximal expression of the tuberization capacity that is determined by the genotype, and therefore, the production of microtubers in sufficient quantity and size. As a result, there are later problems in breaking tuber dormancy. Although the growth responses between in vitro and field-grown tubers are very similar, there is the possibility for the production of in vitro tubers without using growth regulators by modifying in vitro environmental factors, such as light, temperature and mineral nutrition, among others. This review discusses the results of in vitro potato tuberization performed in hormone-free systems on solidified medium, including the effects of environmental factors, composition of medium, genotype and explants. Furthermore, we assess the effects and post-effects of tuberization conditions on the dormancy and sprouting characteristics of microtubers originating from these hormone-free systems.
Caterina Agrimonti, Nelson Marmiroli (Italy) Gene Expression during Transition from Dormancy to Sprouting in Potato Tubers (pp 95-109)
Invited Review: This article reviews the knowledge on the genetic regulation during transition from dormancy to sprouting in potato tuber, to elucidate the molecular mechanisms underlying the physiological and cellular changes driving this complex developmental process. Extensive studies on gene expression were carried out with different tools: differential display, cDNA-AFLP, subtractive libraries, microarrays, quantitative Real Time PCR and proteomic analysis. A high proportion of sequences up- or down-regulated at the end of dormancy are still unknown or match with proteins in databases that have not yet been characterised. Other sequences encode genes involved in hormone metabolism and response, or are transcriptional factors, ribosomal and carrier proteins, or putative regulators of cell growth and division. At the end of dormancy, when the tuber enters in a source condition, a general decrease of synthesis of storage proteins and enzymes involved in biosynthetic metabolism has been observed, as well as modifications in the pattern of proteins associated to membranes. Studies conducted on transgenic plants suggest that phosphate and sucrose levels may play a crucial role in the sink-to-source transition during sprout growth, as well as the reactive oxygen species.
Xin Song, Manjula Bandara, Karen K. Tanino (Canada) Potato Dormancy Regulation: Use of Essential Oils for Sprout Suppression in Potato Storage (pp 110-117)
Invited Mini-Review: Sprout suppression is essential in assuring potato quality. Release of natural tuber dormancy is affected by production as well as storage environmental factors, cultivars and tuber metabolic activities. Plant growth regulators are also shown to play important roles in regulating tuber dormancy. In commercial storage, sprouting is primarily controlled by low temperature combined with chemical inhibitors, such as Chlorpropham (CIPC). However, increasing concerns regarding the safety and environmental impact of chemical residues have increased interest in investigating the potential of alternate sprout inhibitors as well as disease suppressors, including essential oils. Literature has shown carvone, a major component of caraway, dill and spearmint oils, can temporarily inhibit sprouting and long-term sprout inhibition can be achieved by repeated treatments. Carvone plays a role in enhancing degradation of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), a key enzyme that catalyzes the rate limiting reaction in the mevalonate pathway. Carvone and many essential oils exhibit great potential to be used for sprout suppression under commercial storage conditions for both consumption and seed potatoes.
Evgenij V. Mokshin, Alexander S. Lukatkin (Russia), Jaime A. Teixeira da Silva (Japan) Induction of Microtuberization for One-bud Potato Cuttings in Vitro (pp 118-124)
Original Research Paper: The patterns and features of in vitro microtuberization of three Solanum tuberosum L. cultivars, ‘Zhukovskij early’, ‘Nevskij’ and ‘Nikulinskij’ were investigated. The optimum concentration of carbon sources (sucrose, glucose and fructose, singly or in combination) to maximize microtuberization in explants consisting of a single axillary bud and leaf (i.e. one-bud cuttings) were established. ‘Zhukovskij early’ responded best to sucrose, ‘Nikulinskij’ to fructose and ‘Nevskij’ to glucose or any 2-carbon mixture, with the lowest tuberization percentage in any case being 88%. These results were for solid, agarized medium. ‘Nikulinskij’ was then selected, base don the agarized medium trials, as the model plant and similar experiments were conducted in liquid medium with surprising observations: The tuberization index could be increased by incorporating glucose or fructose in the medium for stolon formation, resulting in more tubers and by incorporating sucrose larger and heavier tubers could form.
Zoran Vujčić, Biljana Dojnov, Aleksandra Milovanović, Nataša Božić (Serbia) Purification and Properties of Major Leucyl Aminopeptidase from Solanum tuberosum Tubers (pp 125-130)
Short Communication: Zymogram analysis revealed three isoforms of leucyl aminopeptidase (LAP) using leucine-p-nitroanilide as a substrate in the crude extracts of different potato tuber cultivars. The major LAP isoform, detected in all analyzed potato cultivars, was also active using methionine-p-nitroanilide, alanine-p-nitroanilide and lysine-p-nitroanilide as a substrates. The major LAP from potato tuber was subsequently purified and characterized. Specific LAP activity increased 160-fold by purification of the crude extract. The purified enzyme had a pH optimum of 9.0 and temperature optimum of 40°C. LAP hydrolyzed leucine-p-nitroanilide with a KM of 0.048 mM and a Vmax of 31.56 mM /min. Among a number of inhibitors tested, the most efficient was 1,10-phenanthroline, while ethylene glycol tetraacetic acid (EGTA) stimulated LAP activity. Almost all divalent cations tested, significantly inhibited the enzyme activity. LAP, purified by gel-filtration on Superose 12-FPLC column, had molecular mass of 90 kDa and isoelectric point of 5.45. Sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed one band of 48 kDa. LAP from potato tubers displayed some novel properties among plant LAPs.
Takamitsu Utsukihara, C. Akira Horiuchi (Japan) Biotransformation of Some Compounds using Potato (pp 131-144)
Invited Mini-Review: Biocatalysts have been considered as suitable biochemical systems for the biotransformation of exogenous substrates. For the last 20 years plant cell cultures have been used for the biotransformation of compounds such as terpenoids and alkaloids. In the last decade, various examples of the reduction of ketones to chiral alcohols are reported using fungi or algae. It is known that various enzymes are included in some vegetables and catalyse the oxidation, reduction and hydrolysis of ester. In particular, potatoes contain the enzymes such as polyphenol oxidase (PPO), lypoxygenase (LOX), Solanum tuberosum epoxide hydrolase (StEH), hydroperoxide lyase (HPOlyase), reductase, and hydroxylase. Mironowicz (1998) first reported that the use of whole plant cells from potato and topinambur tubers for the hydrolysis of acetates results in the production of alcohols. Recently, the use of plant enzymatic systems and genetic manipulation approaches to biotransformation has steadily increasing over the past half decade. More recently, we reported that the biotransformation of camphorquinone, 1,2-cyclohexanedione and 2-methylcyclohexanone using various vegetables gives the corresponding alcohols as reduction products. Moreover, other studies have shown the studied oxidation of bisphenol A by polyphenol oxidase in vegetables. The availability of the enzymatic system using vegetables is low cost, with ease of work-up and eco-friendly system for all advantages. In this paper the reduction of various ketones, oxidation of some compounds and hydrolysis of ester with potatoes in vegetables are described.
Beata Szafranek, Janusz Szafranek (Poland) Volatiles of Solanum spp.: Analysis, Composition and Ecological Significance (pp 145-155)
Invited Review: A review of the analysis and composition of volatile organic compounds (VOCs) in Solanum plants of worldwide economic importance – potatoes, tomatoes and aubergines – is presented together with some general comments on this field of research. VOC blends consist of green leaf volatiles (C6 compounds), terpenoids, sesquiterpenoids and aromatics, among other compounds. Two types of sampling are generally applied in VOC trapping: headspace sampling, and direct methods such as extraction and distillation. The structural assignment of VOCs is based mostly on GC and GC-MS procedures: their possibilities and limitations are discussed. In addition to these methods, NMR spectra, which require preparative scale separations, are used for the identification of unknowns. VOCs in Solanum include volatiles emitted by potato and tomato foliage, the aroma of vegetables such as tomatoes, volatiles from cooked potatoes and cooked aubergine fruits, and volatiles from diseased potato tubers. Examples of natural VOC blends, as well as, those induced by insect feeding or infections are given. Comparison of the data on Solanum volatiles reveals compositional similarities and differences. Green leaf volatiles and b-caryophyllene are present in both potato and tomato foliage blends but in different concentrations; the minor components differ in their compositions in these two species. The ecological significance of potato foliage volatiles is briefly presented. Diseases are one of the major problems affecting potato storage. Monitoring of volatiles produced by diseased potatoes for the detection of infections in stored potatoes is described.