A proteomic analysis of storage stress responses in Ipomoea batatas (L.) Lam. tuberous root

During post-harvest storage, tuberous roots of sweet potato (Ipomoea batatas L. Lam.) usually undergo a biotic and abiotic stress influencing protein expression pattern and substance contents. This research compared the change of total proteins and carbohydrate content in tuberous roots of sweet potato during the storage period. The result of the two-dimensional electrophoresis analysis demonstrated that there were 25 differentially expressed proteins between day 0 and day 75 during the storage. Among these proteins, 11 proteins were down-regulated and the other 14 were up-regulated. The results from MALDI-TOF-TOF/MS analyses and mascot database searching showed that 11 of the 25 differentially expressed proteins were identified as store-stress regulated proteins. It was also found that the proteins involved in the energy metabolism and the stress-response were drastically up-regulated, whereas those in biomacromolecule synthesis were markedly down-regulated. Meanwhile, under the experimental conditions, the content of the starch and the cellulose was decreased by more than a quarter and the amylase activity was increased moderately.     

Role of calonyctin on free sugars in relation to starch accumulation in developing sweet potatoes

Calonyctin, a natural plant growth regulator extracted from the leaves of Calonyction aculeatum (L.) House, can promote crop growth and increase crop yield. The specific reasons for this response are unknown. This study was conducted to determine the effect of calonyctin treatment on the free sugars of sweet potato [Ipomoea batatas (L.) Lam.] as related to starch accumulation. The sweet potatoes were grown in the field in 1992, treated by foliar spray with Calonyctin concentrations of 0 (control) and 0.1 activity unit (CTSP) at 20 days after planting (DAP) at the rate of 190 liters of diluted solution/ha., and sampled periodically to determine free sugars. The response of sweet potato to calonyctin was first detected at 40 days after treatment (on 60 DAP). Data indicated that calonyctin treatment significantly increased starch synthesis in storage roots, decreased the fluctuation tendency of total sugar level during the growth period, and kept the sugar level relatively constant with a gradual rise regardless of variations in weather. The level of the reducing sugars in CTSP leaves was higher at 60 and 160 DAP and lower at 100, 120, and 140 DAP. During rainy days (100 DAP), the reducing sugars in CTSP storage roots remained at a lower level when those in controls reached high levels. The sucrose content in CTSP leaves was 40–138% greater than that in controls except at 80 and 120 DAP, and the ratio of sucrose to total nonreducing sugars remained at 100% in CTSP leaves even on rainy and cool days and above 96% in CTSP storage roots except on cool days (140 and 160 DAP), suggesting that calonyctin treatment promoted the synthesis and transfer of sucrose and supplied abundant sugar precursors for starch accumulation in storage roots.Abbreviations DAP days after planting - CTSP calonyctin-treated sweet potato with 0.1 activity unit     

Analysis of the feed-forward effects of sink activity on the photosynthetic source-sink balance in single-rooted sweet potato leaves. I. Activation of RuBPcase through the development of sinks

Single-rooted sweet potato leaves having a petiole with a fragment of stem allocated exceptionally large amounts of photosynthates to tuberous roots, the only major storage organ, throughout an experimental period of 50 d. The increase in photosynthetic activity for CO(2) fixation depended exclusively on the development of sink activity due to the growth of tuberous roots. Thus this model expressed a remarkable feed-forward effect on the photosynthetic source-sink balance. The level of ribulose-1,5-bisphosphate carboxylase (RuBPcase) protein in the leaves increased continuously during the period. The lowered initial as well as total activity of RuBPcase observed at the start of the experiment was raised with the cancellation of the sink-limited state due to the development of tuberous roots. The maximum activity determined after removing some inhibitor(s) from the enzyme by treating the leaf extract with SO(4)(2-) was much greater than the total activity and remained approximately constant throughout the experimental period. The clear decrease in the difference between maximum and total activities with the development of tuberous roots might reflect the reactivation of RuBPcase due to the removal of some inhibitor(s) from the enzyme through the cancellation of the sink-limited state.     

Mycorrhizal differences between genuine roots and tuberous roots of adult plants ofSpiranthes sinensis var.amoena (Orchidaceae)

Genuine roots ofSpiranthes sinensis var.amoena were infected with the mycorrhizal fungusRhizoctonia repens immediately after root formation in autumn. Infection by the mycorrhizal fungus extended, reaching a maximum the following early summer. The amount of living mycorrhizal fungus in the genuine roots dramatically declined in the flowering season, and then the roots decomposed. Tuberous roots were formed in spring. Mycorrhizas were limited to local infections and did not spread along the roots. The infection level of living mycorrhizal fungus in the tuberous roots was less than in the genuine roots throughout the year. The amount of dead fungal coils in the tuberous roots increased as the tuberous roots aged. The mycorrhizal characteritics of tuberous roots ofS. sinensis var.amoena were totally different from those of genuine roots although the tuberous roots morphologically resembled the genuine roots. Contribution No. 96, Laboratories of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba.     

Absence of amylose in sweet potato [Ipomoea batatas (L.) Lam.] following the introduction of granule-bound starch synthase I cDNA

The full-length sense cDNA for sweet potato granule-bound starch synthase I (GBSSI) driven by the CaMV 35S promoter was introduced into the sweet potato by Agrobacterium tumefaciens-mediated transformation. Out of the 26 transgenic plants obtained, one plant showed the absence of amylose in the tuberous root as determined by the iodine colorimetric method. Electrophoresis analysis failed to detect the GBSSI protein, suggesting that gene silencing of the GBSSI gene occurred in the transgenic sweet potato plant. These results demonstrate that starch composition in the tuberous root of sweet potato can be altered by genetic transformation.     

Purification and some properties of starch branching enzyme (Q-enzyme) from tuberous root of sweet potato

The pattern of isoforms of starch branching enzyme II or Q-enzyme II in the tuberous root of sweet potato was distinct from those of other organs; altogether 7 isoforms of QEII were contained in the sweet potato plant. The QEIIf isoform, one of the two major QEII isoforms in the tuberous root, was purified to homogeneity by using a variety of HPLC columns. The purified QEIIf was a monomeric protein with a molecular mass of about 85 kDa. Western blot analysis showed that the polyclonal antibodies raised against the purified QEIIf was significantly reactive to the rice endosperm QEI, but not to the rice endosperm QEIIa. Furthermore, the sweet potato QEIIf reacted with the antiserum raised against the rice endosperm QEI, but not with that against the rice endosperm QEIIa. The results suggest that the sweet potato QEIIf is more similar to the rice endosperm QEI than to the rice endosperm QEIIa.     

Molecular cloning and nucleotide sequence of cDNA for sporamin,the major soluble protein of sweet potato tuberous roots

Summary Sporamin accounts for more than 80% of the total soluble proteins of tuberous roots of sweet potato, but very little, if any, in other tissues of the same plant. In vitro translation of RNA fractions from the tuberous roots in wheat germ extract and subsequent immunoprecipitation with the antibody to sporamin indicated that this protein is synthesized by membrane-bound polysomes as a precursor 4 000 daltons larger than the mature protein. A cDNA expression library was constructed from the total poly(A)⁺ RNA from the tuberous roots by a vector-primer method, and an essentially full-length cDNA clone for the sporamin mRNA was selected by direct immunological screening of the colonies. Northern blot analysis showed that sporamin mRNA is approximately 950 nucleotides in length and is specifically present in tuberous roots and very little, if any, in leaves, petioles and non-tuberous roots. Nucleotide sequence of the cDNA predicts a 37 amino acid extension in the precursor at the amino-terminus of the mature protein.     

Use of Ipomoea trifida germ plasm for sweet potato improvement. 3. Development of 4x interspecific hybrids between Ipomoea batatas (L.) Lam. (2n=6x=90) and I. trifida (H.B.K) G. Don. (2n=2x=30) as storage-root initiators for wild species

Summary More than 28,000 pollinations were carried out between 5 Ipomoea batatas and 41 diploid I. trifida accessions of diverse origins to obtain 4x interspecific hybrids. From the resultant 730 seeds, 248 plants were finally obtained. Ploidy level determination of the progeny showed unexpected results: 52 individuals were hexaploid, 5 were pentaploid, 190 were tetraploid, as expected, and one was not determined. The existence of 5x and 6x progenies from 6x x 2x crosses not only confirmed the presence of 2n gametes but also their successful function in gene flow between ploidy levels and polyploidization within this genus. The progeny and their cultivated parents were planted in an observation field. The cultivated parents produced 0.49 kg/plant or less. Most 4x progenies did not produce storage roots or had very poor yields; nonetheless, and despite their cultivated parents' poor yields, 8 genotypes yielded between 0.81 and 1.50 kg/plant.A new scheme, using the 4x interspecific hybrids, is proposed for evaluating 2x and 4x wild accessions of the section Batatas to which the sweet potato belongs. Other possible uses of the 4x hybrids in breeding and genetics of the sweet potato are also discussed.     

发根农杆菌介导药用甘薯西蒙1号的遗传转化

用发根农杆菌A4分别感染药用甘薯西蒙1号的叶片、茎切段、叶柄等外植体,诱导出毛状根,并对毛状根进行了离体培养.采用L9(34)正交设计法优化甘薯西蒙1号的毛状根诱导条件;PCR扩增检测转化毛状根;用高效液相色谱仪检测了毛状根中咖啡酸的含量.结果表明:转化中茎切段是最合适的外植体,最佳感染时间20 min,共培养最佳时间为2天;PCR扩增检测表明发根农杆菌Ri质粒的T-DNA片段已整合进植物的基因组中;经高效液相色谱仪证实毛状根中含有咖啡酸,含量为0.03792 mg/g.     

甘薯叶片超氧化物歧化酶基因克隆及测序

以甘薯（Ｉｐｏｍｏｅａｂａｔａｔａｓ（Ｌ．）Ｐｏｉｒ）叶为材料提取植物总ＲＮＡ,经反转录后,利用多聚酶链式反应技术,扩增并克隆超氧化物歧化酶基因的ｃＤＮＡ,并进行测序分析。该序列全长４８２ｂｐ,其读码框编码１５２个氨基酸,与国外文献报道的甘薯块根ＳＯＤ基因的ｃＤＮＡ序列相比,具有９９％的同源性。