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A higher concentration of H2O2 was detected in the sense transgenic potato plant (SS4) with the lily chCu,ZnSOD sequence, whereas higher levels of O2(-) was detected in the antisense transgenic plant (SA1) than the WT plant. The elongation growth in SA1 was significantly inhibited by treatment with diphenyleneiodonium, an inhibitor of O2(-) generation, and promoted in the SS4 on treatment with herbicide methyl viologen, a generator of apoplastic O2(-) . Higher concentrations of GAs were detected during plant growth and the early stage of tuberization in SA1. Complete recovery of the above elongation growth and microtuberization pattern in transgenic plants following treatment of GA(3) or an inhibitor of gibberellin synthesis, paclobutrazol, indicate that these changes were mainly caused by active GA levels. In conclusion, a specific ROS (O2(-) ) acts as a signal transducer via GA biosynthetic pathways for the regulation of plant growth and tuber development of potato.

Background: Jasmonates are ubiquitously occurring lipid-derived compounds with signal functions in plant responses to abiotic and biotic stresses, as well as in plant growth and development. Jasmonic acid and its various metabolites are members of the oxylipin family. Many of them alter gene expression positively or negatively in a regulatory network with synergistic and antagonistic effects in relation to other plant hormones such as salicylate, auxin, ethylene and abscisic acid., Scope: This review summarizes biosynthesis and signal transduction of jasmonates with emphasis on new findings in relation to enzymes, their crystal structure, new compounds detected in the oxylipin and jasmonate families, and newly found functions., Conclusions: Crystal structure of enzymes in jasmonate biosynthesis, increasing number of jasmonate metabolites and newly identified components of the jasmonate signal-transduction pathway, including specifically acting transcription factors, have led to new insights into jasmonate action, but its receptor(s) is/are still missing, in contrast to all other plant hormones.

Solanum tuberosum is a frost-sensitive species incapable of cold acclimation. A brief exposure to frost can significantly reduce its yields, while hard frosts can completely destroy entire crops. Thus, gains in freezing tolerance of even a few degrees would be of considerable benefit relative to frost damage. The S. tuberosum cv. Umatilla was transformed with three Arabidopsis CBF genes (AtCBF1-3) driven by either a constitutive CaMV35S or a stress-inducible Arabidopsis rd29A promoter. AtCBF1 and AtCBF3 over-expression via the 35S promoter increased freezing tolerance about 2 degrees C, whereas AtCBF2 over-expression failed to increase freezing tolerance. Transgenic plants of AtCBF1 and AtCBF3 driven by the rd29A promoter reached the same level of freezing tolerance as the 35S versions within a few hours of exposure to low but non-freezing temperatures. Constitutive expression of AtCBF genes was associated with negative phenotypes, including smaller leaves, stunted plants, delayed flowering, and reduction or lack of tuber production. While imparting the same degree of freezing tolerance, control of AtCBF expression via the stress-inducible promoter ameliorated these negative phenotypic effects and restored tuber production to levels similar to wild-type plants. These results suggest that use of a stress-inducible promoter to direct CBF transgene expression can yield significant gains in freezing tolerance without negatively impacting agronomically important traits in potato.

We have examined the changes in carbohydrate metabolism in food yam (Dioscorea esculenta (Lour.) Burk.) tubers and in an economically important spice cum medicinal plant turmeric (Curcuma longa L.) rhizomes under storage. Both specimens showed varied levels of dormancy and sprouting appeared at the end of dormant period. Harvested, fully matured tubers of yam and rhizomes of turmeric were stored in wooden boxes under the conditions of 28+/-2 degrees C temperature and 65-75% relative humidity (RH) in dark. The starch, sugars, enzymes of starch degradation, respiration, glycolysis, tricarboxylic acid (TCA) cycle and oxidative pentose phosphate pathway (PPP) were studied during 1-70 days after harvest (DAH). This investigation revealed that, the starch degradation and the enzymes involved, viz. alpha-amylases and starch phosphorylase showed a lower level of activity during early period of dormancy, while sugar content and enzymes of carbohydrate metabolism increased rapidly during sprouting. The isoenzymic profiles of alpha-amylases showed marked variations in these two phases. The key enzymes of glycolysis, TCA cycle and PPP, viz. aldolase, succinic dehydrogenase, malic dehydrogenase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were increased even before the visible appearance of sprouting and their activities were at their maximum during sprouting. Based of the observations the dormancy period may be distinctly divided into peak period of rest and presprouting period.

Objective: To study the effects of salicylic acid of different concentration (SA) on the growth of Pinellia ternate., Method: SA of different concentration was sprayed to the plant as it grew about 15 cm high. Plant height, total chlorophyll content, activity of SOD, MAD content, photosynthesis speed, intercellular CO2 concentration, the transpiration speed and the leaf temperature were measured after 3 times spray., Result: When 0.5 mmol x L(-1) SA was sprayed, the intercellular CO2 concentration, activity of SOD and photosynthesis speed were increased, while leaf temperature and MDA content were decreased., Conclusion: SA at the concentration of 0.5 mmol x L (-1) was suitable for the growth of P. ternate. It obviously decreased sprout tumble and increased the fresh weight of tuber and the alkaloid content.

Partitioning of carbon dominates intracellular fluxes in both photosynthetic and heterotrophic plant tissues, and has vast influence on both plant growth and development. Recently, much progress has been made in elucidating the structures of the biosynthetic and degradative pathways that link the major and minor pools of soluble carbohydrates to cellular polymers such as starch, heteroglycans and fructans. In most cases, the regulatory properties of these pathways have been elucidated and the enzymes involved have been investigated using reverse genetics approaches. Although many of the results from these approaches were merely confirmatory, several of them were highly unexpected. The challenge ahead is to achieve better understanding of metabolic regulation at the network level in order to develop more rational strategies for metabolic engineering.

Objective: To investigate lipid components of high-yielded Pinellia ternata rhizomes growing in the west of Hubei province., Methods: To determine the lipid chemical components in Pinellia ternata rhizomes with GC-MS method and NIST atlas., Results: Ten components have been found: palmitic acid (I), 9,12-octadecadienoic acid (II), pyrrolidine,1-(1-oxo-7,10-hexadecadienyl) (III), alpha-monpalmitin (IV), 1,3,12-nonadecatriene (V), campesterol (VI), stigmasta-5,22-dien-3-ol (VII), beta-sitosterol (VIII), stigmasta-5,24-dien-3-ol (IX), cycloartenol (X)., Conclusion: The relative contents of five kinds of phytosterol: campesterol 28.96%, stigmasta-5,22-dien-3-ol 9.24%, beta-sitosterol 50.77%, stigmasta-5,24-dien-3-ol 4.74%, cycloartenol 6.25%. Component II, III, V, VI, IX are the first time reported in Pinellia ternata.

Objective: To compare the quality of cultivated Chinese yam (Dioscorea polystachya Turcz.) from Yunnan (Kunming yam) and Henan (Tiegum yam) by determining the content of dry substance in fresh sample and the contents of water extracts, ethanol extracts, starch, protein, crude-fat and polysaccharide in dry sample., Method: The above-mentioned indexes were determined by methods of air desiccation, cold-immersing, hot-immersing, iodine-blue coloration, half Micro-Kjeldahl, Soxhlet extraction and spectrophotometric method respectively., Result: In fresh sample, the content of dry substance of Kunming yam is a little lower than Tiegun yam; in dry sample, all indexes of Kunming yam are higher than or approach to those of Tiegun yam except the content of crude-fat. Especially the content of polysaccharide in Kunming yam is 64% higher than that of Tiegun yam., Conclusion: Kunming yam, with high quality, high yield and good taste, deserves paying close attention as a good variety.

The ability of triadimefon (TDM), a triazolic fungicide, to alter the biochemical constituents and thereby minimizing the days required for sprouting in white yam (Dioscorea rotundata Poir.) tubers during storage under (30+/-2) degrees C in the dark, was studied. TDM at 20 mg/L was given to tubers by dipping the tubers in treatment solution containing 20 mg/L TDM on 10, 25 and 40 d after storage (DAS). Starch, sugars, protein, amino acid contents as well as protease and alpha-amylase activities were estimated on 15, 30 and 45 DAS from two physiological regions viz., apical and basal regions of the tubers. In normal conditions (control) sprouting occurred on 70 to 80 DAS. The starch content decreased, while protein, amino acid, sugar contents and protease and alpha-amylase activities were increased due to TDM treatment and led to early sprouting.

The aim of this investigation is introducing the use of continuous and semi-continuous bioreactors and their functions at shoot multiplication and microtuberization of potato. The study shows that the explants have several nodes and when they are suspended continuously under the liquid culture medium, the shoot micropropagations and microtuberization was inhibited. The surfaces of the explants were formed callus and subsequently, they were died. However, in the semicontinuous bioreactor, with the periodical pumping of the nutritional medium the explants aren't continuously suspended under the nutritional solution. The shoot micropropagation, the leaf growth and, the root formation are suitable. In the microtuber inductive medium, the numerous of the tubers are induced. They were sessile tubers. The dormancy of the tubers are long-term, spourting after 3-4 months in the room conditions.

The main aim of this investigation is the understanding of how microtubers are formed out of auxiliary buds in induced conditions. In the induced buds, meristematical cells with high cytoplasmic and nuclear stain ability expand deeper into the inner sections of the buds, comparing with non-induced buds, which the area is restricted to the apical regions. The first sign of microtuberization is the increase in size of cortical parenchyma cells in lower section and also increase in mitosis divisions in inner sections of the meristems. Most of the growth rates occur in the induced medium along the length and the width of the cells. It is also considered that the diametric growth of the tubers and the base of the leaves on the tubers begin their radial growth. The cortical parenchyma cells begin forming amidon grains during their vacuolar extension at extending the internodes much earlier than pith parenchyma cells. The extension of cells in sub-apical region plays an important role in the longitudinal growth of tubers. In the first stages, the growth of tubers results from the change in the dimensions of cortical and pith parenchyma cells, due to the reproduction of apical meristem and later, mainly from the growth of the productive tissue in the pith parenchyma. Longitudinal growth is initially grater than the growth in diameter; however with shift in the position of vacuoles and their arrangement across rather than along the tubers, the growth pattern begins to change and lateral growth catches on and exceeds longitudinal growth. In fully grown tubers, pith parenchyma cells are larger than the cells in cortical parenchyma.

We have achieved the symbiotic cultivation of an apparently achlorophyllous orchid, Epipogium roseum Lindl., with a mycorrhizal fungus isolated from an underground organ of this orchid. Although the seed germination rate was extremely low, subsequent growth from protocorm to flowering was induced in a medium containing volcanic soils and sawdust. Stolons elongated from each protocorm, and rhizomes were formed at certain intervals on the stolons. Some of the rhizomes developed into a coralloid form, and tubers were formed from the coralloid rhizomes. The coralloid rhizomes degenerated concurrently with maturation of the tubers. Six months after seed sowing, around 80 tubers were produced from a single protocorm. An inflorescence appeared from each of the large tubers, and the process to flowering was observed in one of these. Consequently, the developmental processes from seed to flowering in E. roseum was clearly revealed in this study.

Somatic hybrids of potato with a cultivated relative, Solanum stenotomum also called Solanum tuberosum Stenotomum group, were evaluated for their physiological and agronomical characteristics as well as the stability of the introgressed resistance to bacterial wilt, caused by Ralstonia solanacearum, after a long-term in vitro conservation for more than 5 years. Analysis of photosynthesis showed that the PEPC/Rubisco ratio remained lower than 0.5 for all vitroplants of potato and the somatic hybrids, except for the relative species. This indicates that the carbon metabolism is heterotrophic (ratio>1) for S. stenotomum, and autotrophic for potato and the somatic hybrids (ratio<1). In both in vitro and greenhouse conditions, potato and the somatic hybrids produced few bigger tubers, while many small tubers were obtained from the relative. The hybrid tubers were morphologically intermediate. The starch content of hybrid tubers was much lower than that of potato, but similar to that of the relative species. Interestingly, the level of bacterial resistance, introgressed from S. stenotomum into potato, was shown to be very stable and remained as high as that of the relative after a long-term period of in vitro conservation.

Rhizome fragments (referred to as "fragments") and tubers of Equisetum arvense L. were cultured in order to investigate their competence with respect to vegetative reproduction. The starch concentration of the fragments was lower than that of the tubers, but the initial growth of new individuals from these fragments was superior to that from tubers obtained from the same dry mass. This superior growth was due to the large number of buds (grown from nodes) and aerial shoots on the fragments. The competence for vegetative reproduction depended on the relationship between the stored starch and the number of buds.

Nymphaea and Nuphar (Nymphaeaceae) share an extra-axillary mode of floral inception in the shoot apical meristem (SAM). Some leaf sites along the ontogenetic spiral are occupied by floral primordia lacking a subtending bract. This pattern of flower initiation in leaf sites is repeated inside branching flowers of Nymphaea prolifera (Central and South America). Instead of fertile flowers this species usually produces sterile tuberiferous flowers that act as vegetative propagules. N. prolifera changes the meristem identity from reproductive to vegetative or vice versa repeatedly. Each branching flower first produces some perianth-like leaves, then it switches back to the vegetative meristem identity of the SAM with the formation of foliage leaves and another set of branching flowers. This process is repeated up to three times giving rise to more than 100 vegetative propagules. The developmental morphology of the branching flowers of N. prolifera is described using both microtome sections and scanning electron microscopy.

Despite the long history of breeding potatoes resistant to Phytophthora infestans, this oomycete is still economically the most important pathogen of potato worldwide. The correlation of high levels of resistance to late blight with a long vegetation period is one of the bottlenecks for progress in breeding resistant cultivars of various maturity types. Solanum phureja was identified as a source of effective late blight resistance, which was transferred to the cultivated gene pool by interspecific crosses with dihaploids of Solanum tuberosum. A novel major resistance locus, Rpi-phu1, derived most likely from S. phureja and conferring broad-spectrum resistance to late blight, was mapped to potato chromosome IX, 6.4 cM proximal to the marker GP94. Rpi-phu1 was highly effective in detached leaflet, tuber slice and whole tuber tests during 5 years of quantitative phenotypic assessment. The resistance did not show significant correlation with vegetation period length. Our findings provide a well-characterized new source of resistance for breeding early and resistant-to-P. infestans potatoes.

Objective: To study the effects of potassium salts on direct induction of microtubers from different explants in Pinellia ternata., Method: Leaves, petioles and tubers were cut and cultured on the medium with different kinds of potassium salts and plant growth regulators., Result and Conclusion: Low concentration of potassium salts, which were lower than 4.02 mmol x L(-1), could promote the microtuber formation in vitro. While high concentration of potassium salts, which were more than 12.06 mmol x L(-1), inhibited the formation of microtubers.

A number of parameters linked to the selection of potato tubers were evaluated with regard to their potential to influence acrylamide formation in French fries. The formation of acrylamide, which is a potential human carcinogen, can be minimized for a big extent by the selection of an appropriate tuber. This study focused on the following selection criteria: variety as influenced by storage time and soil type, underwater weight, and tuber size. A total of 16 varieties were compared, concerning their potential for acrylamide formation. From that survey, certain varieties, such as Tebina and Quincy, could be appointed as unsuitable for frying. The differences in the potential of acrylamide formation between the varieties could mainly be explained by the reducing sugar content of the potato (R2 = 0.82, n = 96). The investigated type of soil and storage time at 8 degrees C appeared to have a minor influence on the acrylamide formation during frying. On the other hand, the tuber size of the potato did contribute in a significant manner to the acrylamide formation. Smaller tubers were more susceptible to acrylamide formation and should be avoided in the frying process. The last selection parameter, the underwater weight, appeared to be of minor importance in the acrylamide formation. On the basis of these simple selection criteria, it is possible to make a first screening of potatoes to reduce the acrylamide formation during frying.

Modification of tuber carbohydrate metabolism by the tuber-specific expression of a yeast invertase targeted to the cytosol or apoplast has previously been demonstrated to have diverse effects on tuber growth and metabolism. In the current study, we generated plants exhibiting tuber-specific expression of the same enzyme targeted to the vacuole. Enzymatic analysis of the carbohydrate levels of the tuber revealed dramatic decreases in sucrose content coupled with large increases in the levels of glucose and hexose phosphates, but unaltered starch content in the transformants. Analysis of the key enzyme of glycolysis suggests that this pathway is down-regulated in the transformants. Despite these changes in metabolite pools and enzyme activity, few consistent changes could be observed in the estimated metabolic fluxes following incubation of isolated tuber discs in labelled glucose. The analysis of the relative levels of a wide range of metabolites using a gas chromatography-mass spectrometry (GC-MS)-based metabolite profiling method revealed large changes in the levels of fructose and decreases in a range of other sugars, but very few changes in the contents of organic and amino acids. This metabolic profile is remarkably consistent with that obtained following expression of the invertase in the apoplastic compartment, providing circumstantial evidence for the endocytotic trafficking of sugars within potato tuber parenchyma. Finally, the results of this study are compared with those from other plant species and the relative roles of the vacuolar isoform of the enzyme are contrasted.

Potato tubers were engineered to express a bacterial gene encoding 1-deoxy-D-xylulose 5-phosphate synthase (DXS) in order to investigate the effects of perturbation of isoprenoid biosynthesis. Twenty-four independent transgenic lines out of 38 generated produced tubers with significantly elongated shape that also exhibited an early tuber sprouting phenotype. Expression analysis of nine transgenic lines (four exhibiting the phenotype and five showing a wild-type phenotype) demonstrated that the phenotype was strongly associated with dxs expression. At harvest, apical bud growth had already commenced in dxs-expressing tubers whereas in control lines no bud growth was evident until dormancy was released after 56-70 d of storage. The initial phase of bud growth in dxs tubers was followed by a lag period of approximately 56 d, before further elongation of the developing sprouts could be detected. Thus dxs expression results in the separation of distinct phases in the dormancy and sprouting processes. In order to account for the sprouting phenotype, the levels of plastid-derived isoprenoid growth regulators were measured in transgenic and control tubers. The major difference measured was an increase in the level of trans-zeatin riboside in tubers at harvest expressing dxs. Additionally, compared with controls, in some dxs-expressing lines, tuber carotenoid content increased approximately 2-fold, with most of the increase accounted for by a 6-7-fold increase in phytoene.

The length of potato tuber dormancy depends on both the genotype and the environmental conditions during growth and storage. Abscisic acid (ABA) has been shown to play a critical role in tuber dormancy control but the mechanisms regulating ABA content during dormancy, as well as the sites of ABA synthesis, and catabolism are unknown. Recently, a temporal correlation between changes in ABA content and certain ABA biosynthetic and catabolic genes has been reported in stored field tubers during physiological dormancy progression. However, the protracted length of natural dormancy progression complicated interpretation of these data. To address this issue, in this study the synthetic dormancy-terminating agent bromoethane (BE) was used to induce rapid and highly synchronous sprouting of dormant tubers. The endogenous ABA content of tuber meristems increased 2-fold 24 h after BE treatment and then declined dramatically. By 7 d post-treatment, meristem ABA content had declined by >80%. Exogenous [(3)H]ABA was readily metabolized by isolated meristems to phaseic and dihydrophaseic acids. BE treatment resulted in an almost 2-fold increase in the rate of ABA metabolism. A differential expression of both the StNCED and StCYP707A gene family members in meristems of BE-treated tubers is consistent with a regulatory role for StNCED2 and the StCYP707A1 and StCYP707A2 genes. The present results show that the changes in ABA content observed during tuber dormancy progression are the result of a dynamic equilibrium of ABA biosynthesis and degradation that increasingly favours catabolism as dormancy progresses.

The aim of this work was to evaluate the influence of elevating the cytosolic activity of phosphoglucomutase (PGM; EC 5.4.2.2) on photosynthesis, growth and heterotrophic metabolism. Here we describe the generation of novel transgenic plants expressing an Escherichia coli phosphoglucomutase (EcPGM) under the control of the 35S promoter. These lines were characterised by an accumulation of leaf sucrose, despite displaying no alterations in photosynthetic carbon partitioning, and a reduced tuber starch content. Determinations of the levels of a wide range of other metabolites revealed dramatic reductions in maltose and other sugars in leaves of the transformants, as well as a modification of the pattern of organic and amino acid content in tubers of these lines. Intriguingly, the transgenics also displayed a dramatically delayed rate of sprouting and significantly enhanced rate of respiration, however, it is important to note that the severity of these traits did not always correlate with the level of transgene expression. These results are discussed in the context of current understanding of the control of respiration and the breaking of tuber dormancy.

A novel potato micro-tuber-inducing compound was isolated from the culture broth of Lasiodiplodia theobromae Shimokita 2. The structure of the isolated compound was determined as (3R,6S)-6-hydroxylasiodiplodin by means of spectroscopic analyses, the modified Mosher method, and chemical conversion. The compound showed potato micro-tuber-inducing activity at a concentration of 10(-4) M, using the culture of single-node segments of potato stems in vitro.

Pyrimidine nucleotides are of general importance for many aspects of cell function, but their role in the regulation of biosynthetic processes is still unclear. In this study, we investigate the influence of a decreased expression of UMP synthase (UMPS), a key enzyme in the pathway of de novo pyrimidine synthesis, on biosynthetic processes in growing potato (Solanum tuberosum) tubers. Transgenic plants were generated expressing UMPS in the antisense orientation under the control of the tuber-specific patatin promoter. Lines were selected with markedly decreased expression of UMPS in the tubers. Decreased expression of UMPS restricted the use of externally supplied orotate for de novo pyrimidine synthesis in tuber tissue, whereas the uridine-salvaging pathway was stimulated. This shift in the pathways of UMP synthesis was accompanied by increased levels of tuber uridine nucleotides, increased fluxes of [(14)C]sucrose to starch and cell wall synthesis, and increased amounts of starch and cell wall components in the tubers, whereas there were no changes in uridine nucleotide levels in leaves. Decreased expression of UMPS in tubers led to an increase in transcript levels of carbamoylphosphate synthase, uridine kinase, and uracil phosphoribosyltransferase, the latter two encoding enzymes in the pyrimidine salvage pathways. Thus, the results show that antisense inhibition of the de novo pathway of pyrimidine synthesis leads to a compensatory stimulation of the less energy-consuming salvage pathways, probably via increased expression and activity of uridine kinase and uracil phosphoribosyltransferase. This results in increased uridine nucleotide pool levels in tubers and improved biosynthetic performance.

A plant growth regulator, theobroxide, which produces potato tubers under noninduced long-day conditions, was synthesized in four steps from dihydrotoluene.

Constitutive antisense inhibition of the cytosolic isoform of phosphoglucomutase in the potato (Solanum tuberosum L.) results in restriction of photosynthesis, growth inhibition and modified tuber morphology, and a severe restriction of tuber starch synthesis. Here we describe the consequences of the tuber-specific expression of an Escherichia coli phosphoglucomutase in the cytosol. Analysis of [14C]glucose metabolism by tuber discs isolated from wild type and transformants revealed that the rates of sucrose and starch synthesis were unaltered but that the rate of glycolysis was depressed in the transgenics. The transformant tubers also contained dramatically reduced amino acid content and significantly higher levels of ADP, but were characterized by elevated levels of Krebs cycle intermediates and an unaltered rate of respiration. In addition to these metabolic consequences of the overexpression of the E. coli enzyme, we observed morphological changes in tubers, with the transformants having a smaller number of larger tubers which exhibited delayed rates of sprouting with respect to the wild type. These results are discussed with respect to current models of the regulation of central plant metabolism and tuber dormancy.

Objective: To study the effects of different factors on direct induction of microtubers. These factors included plant growth substances, casein hydrolysate (CH), active carbon (AC), polyethylene glycol (PEG 4000), sucrose and glucose., Method: Using the orthogonal design method., Result and Conclusion: The optimal media to directly induce microtubers from leaves were MS + MET 0.5 mg x L(-1) + 6-BA 0.5 mg x L(-1) + sucrose 3% and MS+ 6-BA 0.5 mg x L(-1) + IAA 0.5 mg x L(-1) + sucrose 3%. Optimal media to directly induce microtubers from tubers were MS + 6-BA 1.0 mg x L(-1) + PEG 5% + sucrose 5% and MS+ CH 500 mg x L(-1) + MET 0.5 mg x L(-1) + 6-BA 0.5 mg x L(-1) + AC 0.5% + sucrose 5%. Media suitable for plantlet growth were MS + 6-BA 0.5 mg x L(-1) + IAA 0.5 mg x L(-1) + AC 0.5% + sucrose 5% and MS + MET 0.5 mg x L(-1) + 6-BA 0.5 mg x L(-1) + sucrose 3%.

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.

The effect of selenium (Se) treatments on potato growth and Se, soluble sugar, and starch accumulation was investigated. Potato plants were cultivated in quartz sand without or with sodium selenate (0, 0.075, 0.3 mg Se kg(-1) sand). In young potato plants, Se treatment resulted in higher starch concentrations in upper leaves. The tuber yield of Se-treated potato plants was higher and composed of relatively few but large tubers. At harvest, the starch concentration in tubers did not differ significantly between treatments. The higher Se addition (0.3 mg Se kg(-1)) may have delayed the aging of stolons and roots, which was observed as high concentrations of soluble sugar and starch. Together with the earlier results showing elevated starch concentration in Se-treated lettuce, the findings of this research justify the conclusion that Se has positive effects also on potato carbohydrate accumulation and possibly on yield formation.

Iodine-saturated atmosphere was found to inhibit the sprouting of potato (Solanum tuberosum L.) tubers. The iodine concentration in tuber tissues increased as a function of exposure length, and the onset of inhibition of sprouting was found to depend on tubers genotype. During the time-course of the treatment, the transcription of polyphenol oxidases (EC 1.10.3.1 and EC 1.14.18.1) was undetectable in tuber peel, whereas in bud tissues featured an increase, followed by a decrease occurring simultaneously with the suppression of sprouting. The treatment of tubers with iodine strongly affected the expression of polyphenol oxidases at the transcriptional level. Polyphenol oxidase activity in buds poorly reflected the corresponding level of transcription; similarly, little differences were found among the enzyme isoforms expressed in buds as a function of length of exposure to iodine. These findings suggest that the induction of polyphenol oxidases mRNAs transcription could probe the inhibition of sprouting by iodine.

Many gram-negative bacteria employ N-acylhomoserine lactones (AHL) to regulate diverse physiological processes in concert with cell population density (quorum sensing [QS]). In the plant pathogen Erwinia carotovora, the AHL synthesized via the carI/expI genes are responsible for regulating the production of secreted plant cell wall-degrading exoenzymes and the antibiotic carbapen-3-em carboxylic acid. We have previously shown that targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in planta of the cognate AHL signaling molecules N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL), which in turn, were able to complement a carI-QS mutant. In the present study, we demonstrate that transgenic potato plants containing the yenI gene are also able to express AHL and that the presence and level of these AHL in the plant increases susceptibility to infection by E. carotovora. Susceptibility is further affected by both the bacterial level and the plant tissue under investigation.

Objective: To determine the alkaloids content of Pinellia ternate in different growing time for finding out the best harvest time., Methods: The alkaloid was extracted by chloroform from Pinellia ternate and tested at 417 nm with the spectroscopy by acid dye. The result was analyzed in One-Way ANOVA., Results: The calibration curve of alkaloid was linear( r = 0.9989). The recovery rate was perfect (100.1%). The alkaloids content in different growing time had very significant difference ( F = 12.789, P < 0.01)., Conclusion: This method is simple and quick. The alkaloids content in whole seedling stage is higher than that in other growing stages, while the mean total alkaloids output per plant is the highest in intensive seedling-downfallen stage which is considered as the best harvest time.

Virus induced gene silencing (VIGS) is increasingly used to generate transient loss-of-function assays and has potential as a powerful reverse-genetics tool in functional genomic programs as a more rapid alternative to stable transformation. A previously described potato virus X (PVX) VIGS vector has been shown to trigger silencing in the permissive host Nicotiana benthamiana. This paper demonstrates that a PVX-based VIGS vector is also effective in triggering a VIGS response in both diploid and cultivated tetraploid Solanum species. We show that systemic silencing of a phytoene desaturase gene is observed and maintained throughout the foliar tissues of potato plants and was also observed in tubers. Here we report that VIGS can be triggered and sustained on in vitro micropropagated tetraploid potato for several cycles and on in vitro generated microtubers. This approach will facilitate large-scale functional analysis of potato expressed sequence tags and provide a noninvasive reverse-genetic approach to study mechanisms involved in tuber and microtuber development.

Companion cell-specific expression of a cytosolic invertase from yeast ( Saccharomyces cerevisiae) was used as a tool to synthesise oligosaccharides in the sieve element/companion cell complex and study whether oligosaccharides could be transported in the phloem of an apoplastically loading species. Potato ( Solanum tuberosum L.) plants expressing the invertase under the control of the Agrobacterium tumefaciens rolC promoter produced the trisaccharide 6-kestose in leaves, which was transported via the phloem and accumulated in tubers of transgenic plants. In graft experiments with rolC invertase plants as scion and wild-type rootstocks, 6-kestose accumulated in tubers to levels comparable to sucrose. This shows that long-distance transport of oligosaccharides is possible in apoplastically loading plants, which normally transport only sucrose. The additional transport route for assimilates neither led to elevated photosynthetic activity nor to increased tuber yield. Enhanced sucrose turnover in companion cells caused large amounts of glucose and fructose to be exuded from leaf petioles, and elevated levels of sucrose were detected in phloem exudates. While the latter indicates a higher capacity for sucrose loading into the phloem due to increased metabolic activity of companion cells, the massive release of hexoses catalysed by the invertase seemed to interfere with assimilate delivery to sink organs.

Previous spaceflight reports attribute changes in plant ultrastructure to microgravity, but it was thought that the changes might result from growth in uncontrolled environments during spaceflight. To test this possibility, potato explants were examined (a leaf, axillary bud, and small stem segment) grown in the ASTROCULTURETM plant growth unit, which provided a controlled environment. During the 16 d flight of space shuttle Columbia (STS-73), the axillary bud of each explant developed into a mature tuber. Upon return to Earth, tuber slices were examined by transmission electron microscopy. Results showed that the cell ultrastructure of flight-grown tubers could not be distinguished from that of tuber cells grown in the same growth unit on the ground. No differences were observed in cellular features such as protein crystals, plastids with starch grains, mitochondria, rough ER, or plasmodesmata. Cell wall structure, including underlying microtubules, was typical of ground-grown plants. Because cell walls of tubers formed in space were not required to provide support against the force due to gravity, it was hypothesized that these walls might exhibit differences in wall components as compared with walls formed in Earth-grown tubers. Wall components were immunolocalized at the TEM level using monoclonal antibodies JIM 5 and JIM 7, which recognize epitopes of pectins, molecules thought to contribute to wall rigidity and cell adhesion. No difference in presence, abundance or distribution of these pectin epitopes was seen between space- and Earth-grown tubers. This evidence indicates that for the parameters studied, microgravity does not affect the cellular structure of plants grown under controlled environmental conditions.

Using the yeast (Saccharomyces cerevisiae) two-hybrid system and a potato (Solanum tuberosum) KNOX protein, designated POTH1, as bait, we have identified seven distinct interacting proteins from a stolon library of potato. All seven cDNAs are members of the BEL1-like family of transcription factors. Among these proteins, there are at least four regions of high sequence conservation including the homeodomain, the proline-tyrosine-proline three-amino acid loop extension, the SKY box, and a 120-amino acid region upstream from the homeodomain. Through deletion analysis, we identified a protein-binding domain present in the carboxy end of the KNOX domain of POTH1. The protein-binding domain in the BEL1 protein is located in the amino-terminal one-half of the 120-residue conserved region of the BELs. RNA-blot analysis showed differential patterns of RNA accumulation for the BELs in various potato organs. The level of StBEL5 mRNA increased in response to a short-day photoperiod in both leaves and stolons. Similar to sense mutants of POTH1, transgenic lines that overexpressed StBEL5 exhibited enhanced tuber formation even under noninductive conditions. Unlike POTH1 sense lines, however, these BEL lines did not exhibit the extreme leaf and stem morphology characteristic of KNOX overexpressers and displayed a more rapid rate of growth than control plants. Both StBEL5 and POTH1 sense lines exhibited an increase in cytokinin levels in shoot tips. StBEL5 lines also exhibited a decrease in the levels of GA 20-oxidase1 mRNA in stolon tips from long-day plants. Our results demonstrate an interaction between KNOX and BEL1-like transcription factors of potato that may potentially regulate processes of development.

Potato MADS box 1 (POTM1) is a member of the SQUAMOSA-like family of plant MADS box genes isolated from an early stage tuber cDNA library. The RNA of POTM1 is most abundant in vegetative meristems of potato (Solanum tuberosum), accumulating specifically in the tunica and corpus layers of the meristem, the procambium, the lamina of new leaves, and newly formed axillary meristems. Transgenic lines with reduced levels of POTM1 mRNA exhibited decreased apical dominance accompanied by a compact growth habit and a reduction in leaf size. Suppression lines produced truncated shoot clusters from stem buds and, in a model system, exhibited enhanced axillary bud growth instead of producing a tuber. This enhanced axillary bud growth was not the result of increased axillary bud formation. Tuber yields were reduced and rooting of cuttings was strongly inhibited in POTM1 suppression lines. Both starch accumulation and the activation of cell division occurred in specific regions of the vegetative meristems of the POTM1 transgenic lines. Cytokinin levels in axillary buds of a transgenic suppression line increased 2- to 3-fold. These results imply that POTM1 mediates the control of axillary bud development by regulating cell growth in vegetative meristems.

Plants adjust their sink-organ growth rates, development and distribution of dry matter in response to whole-plant photosynthate status. To advance understanding of these processes, potato (Solanum tuberosum L.) plants were subjected to CO(2) and light flux treatments, and early tuber growth was assessed. Atmospheric CO(2) (700 or 350 micro mol mol(-1)) and light flux (shade and control illumination) treatments were imposed at two growth stages: tuber initiation (TI) and tuber bulking (TB). Elevated CO(2) increased accumulation of total net biomass when imposed at both stages, and increased tuber growth rate by about 36 %, but did not increase the number of tubers. Elevated CO(2) increased the number of cells in tubers at both TI and TB stages, whereas shade substantially decreased the number of cells at both stages. Generally, treatments did not affect cell volume or the proportion of nuclei endoreduplicating (repeated nuclear DNA replication in the absence of cell division), but the shade treatment led to a decrease in cell volume at TB and a decrease in endoreduplication at TI. Elevated CO(2) increased, and shade decreased, glucose concentration and soluble invertase activity in the cambial zones at both TI and TB, whereas sucrose concentration and activities of glucokinase, fructokinase, cell-wall-bound invertase and thymidine kinase were unaffected. Modulation of tuber cell division was responsible for much of the growth response to whole-plant photosynthate status, and treatments affected cambial-zone glucose and soluble invertase in a pattern suggesting involvement of a glucose signalling pathway.

The major purpose of these experiments were to investigate growth of potato storage organs and starch synthesis in minitubers at slow horizontal clinorotation (2 rpm), which partly mimics microgravity, and a secondary goal was to study the activity and localization of phosphorylase (EC 2.4.1.1) in storage parenchyma under these conditions. Miniplants of Solanum tuberosum L. (cv Adreta) were grown in culture for 30 days for both the vertical control and the horizontal clinorotation. During long-term clinorotation, an acceleration of minituber formation, and an increase of amyloplast number and size in storage parenchyma cells, as well as increased starch content, was observed in the minitubers. The differences among cytochemical reaction intensity, activity of phosphorylase, and carbohydrate content in storage parenchyma cells of minitubers grown in a horizontal clinostat were established by electron-cytochemical and biochemical methods. It is shown that high phosphorylase activity is correlated with increased starch content during extended clinorotation. The results demonstrate the increase in carbohydrate metabolism and possible accelerated growth of storage organs under the influence of microgravity, as mimicked by clinorotation; therefore, clinorotation can be used as a basis for future studies on mechanisms of starch synthesis under microgravity., (c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.)

Starch represents the most important carbohydrate used for food and feed purposes. With the aim of increasing starch content, we decided to modulate the adenylate pool by changing the activity of the plastidial adenylate kinase in transgenic potato plants. As a result, we observed a substantial increase in the level of adenylates and, most importantly, an increase in the level of starch to 60% above that found in wild-type plants. In addition, concentrations of several amino acids were increased by a factor of 2-4. These results are particularly striking because this genetic manipulation also results in an increased tuber yield. The modulation of the plastidial adenylate kinase activity in transgenic plants therefore represents a potentially very useful strategy for increasing formation of major storage compounds in heterotrophic tissues of higher plants.

An on-line laser micrometer system was applied to measurement of diurnal change in potato (Solanum tuberosum L.) tuber growth. Diameters of the potato tuber were scanned by moving a laser micrometer along the longitudinal axis of the tuber at constant speed, and tuber volume was evaluated as an aggregate of thin discs. A single potato tuber, without competitive sink tubers in the plant, was grown in controlled air at 20 degrees C and 80% RH, and tuber volume was measured at 30 min intervals. During the growth experiment, the potato tuber increased in size without any inhibitory effect of periodical laser beam irradiation. Greatest expansion generally occurred during the early night, and transient contraction of the tuber occurred at the beginning of the light period.