Japanese Yam Research Articles

Effect of Yam (Dioscorea alata Compared to Dioscorea japonica) on Gastrointestinal Function and Antioxidant Activity in Mice

ABSTRACT: Effects of Chinese yam (Dioscorea alata) and Japanese yam (Dioscorea japonica) on gastrointestinal functions including intestinal microflora and intestinal enzymes' activities, as well as antioxidant protection against lipopolysaccharide (LPS)‐induced oxidative damage, in Balb/cA mice were examined. In part I, mice were fed yam‐supplemented diet for 4 or 8 wk, and killed with carbon dioxide. In part II, mice were fed yam‐supplemented diet for 4 wk, and followed by intraperitoneal LPS treatment (i.p. 4 mg/kg bodyweight). The intake of Chinese yam and Japanese yam significantly changed intestinal microflora, in which the colony numbers of Bifidobacterium and Lactobacillus were increased and the colony numbers of Clostridium perfringens were decreased (P < 0.05). The intake of both Chinese and Japanese yams also significantly elevated the activity of leucine aminopeptidase and lipase (P < 0.05), and the activities of sucrase and maltase were increased only in 20% yam‐treated groups (P < 0.05). The preintake of yam significantly alleviated subsequent LPS‐induced oxidative injury by decreasing lipid oxidation level and fibronectin production and elevating superoxide dismutase activity (P < 0.05). Both Chinese and Japanese yams contained dietary fibers, polyphenols, and flavonoids, which may contribute to the observed gastrointestinal function and antioxidant protection. These results suggest that both Chinese yam and Japanese yam were beneficial for intestinal health and oxidation prevention.

Konjak mosaic virus: the complete nucleotide sequence of the genomic RNA and its comparison with other potyviruses

Konjak mosaic virus (KoMV) belongs to the genus Potyvirus, family Potyviridae. The complete nucleotide sequence of KoMV F isolate (KoMV F) was determined. The genome is 9,544 nucleotides long excluding the 3' terminal poly A tail and encodes a typical potyviral 350-kDa polyprotein of 3,087 amino acids. Phylogenetic analysis using known potyvirus polyproteins shows that KoMV constitutes a branch with yam mosaic virus, close to another branch including Japanese yam mosaic virus, turnip mosaic virus, scallion mosaic virus and lettuce mosaic virus. The 3' terminal 1,842 nucleotides of a different isolate of KoMV, K-2, was also determined, covering the C-terminal 292 amino acids of the nuclear inclusion protein b (NIb), coat protein (CP), and the 3' untranslated region. The amino acid sequences of the KoMV F CP and the nucleotide sequences of the KoMV F 3' untranslated region showed 92.5 and 90.5% identity to the corresponding genes of K-2, 88.7-96.8 and 92.7-94.4% to those of Zantedeschia mosaic virus (ZaMV) isolates, 87.5-89.7% and 85.5-90.3% to those of Japanese hornwort mosaic virus (JHMV) isolates. These results showed that KoMV is a distinct potyvirus and that KoMV, ZaMV, and JHMV are members of the same potyvirus species. Considering that KoMV was the first of these to be described, ZaMV and JHMV may be considered isolates of KoMV.

Improvement of micropropagation of Japanese yam using liquid and gelled medium culture

Micropropagation of an elite cultivar of Dioscorea japonica Thunb. was improved. In an initiation culture, the fresh weight increased the most in 0.1% gellan gum medium to 633.0 mg, and then in 0.2% gellan gum medium to 204.3 mg, but the 0.1% gellan gum medium increased the number of hyperhydric individuals. For shoot proliferation, liquid medium was superior to solid medium in the number of nodes (6.9 and 2.1, respectively) and the fresh weight (283.4 and 51.9, respectively). 6-Benzylaminopurine (BA) at 0.44 μM increased the number of nodes to 7.0, shoots to 2.6, and the fresh weight to 336.0 mg. Linsmaier and Skoog (LS) medium at 40 mL was superior to 20 mL in producing more nodes (18.6 and 5.6, respectively), shoots (3.6 and 2.7, respectively) and fresh weight (783.0 and 278.0, respectively). Static culture increased the number of nodes and the fresh weight more compared with rotary culture. For rooting, agar and gellan gum media were superior to the liquid medium in rooting frequency, but the number of roots in these media was inferior to the liquid medium. Acclimated nursery plants showed no variation in main traits.

Interaction between Effects of Photoperiod and Plant Growth Regulators on the Development of Tubers and Inflorescences in Japanese Yams (Dioscorea japonica)

The interaction between 8- and 24-hr photoperiods and plant growth regulators (PGR) (gibberellin A3 (GA3) and uniconazole-P (Uni)) on the development of the main shoots, aerial tubers (bulbils) and new tubers (below ground), and inflorescences (spikes) in Japanese yam (Dioscorea japonica Thunb.) plants was examined. Within the same PGR treatment, the main shoots of plants grown under the 24-hr photoperiod (constant light, LD) were longer than those grown under the 8-hr photoperiod (SD) in all season; under LD and SD, the main shoots of the GA3-treated plants were the same size as shoots sprayed with water (control), whereas the main shoots of the Uni-treated plants were significantly shorter. Under LD, whereas the control and PGR-treated plants produced a negligible amount of aerial tubers, under SD, their development was severely inhibited by GA3 treatment. During the early growing period, the fresh weight of new tubers and that of the combined fresh weight of aerial and new tubers in plants grown under SD were heavier than those grown under LD. From the middle to the end of the growing period, the development of aerial and new tubers in plants grown under LD accelerated so that the difference between the final fresh weights of the combined fresh weight of aerial and new tubers in plants grown under SD and those grown under LD at harvest became small. Although, there was not such LD promoting effect of those growth as would be observed in D.opposita cv. Ichoimo and Nagaimo. Under SD, the new tubers development were significantly promoted by GA3 treatment because the inhibition of aerial tubers development by GA3 treatment promotes the diversion of photosynthates stored in shoots to growth of new tubers. Under SD, plants grown developed one flush of inflorescences in June, whereas those grown under LD developed a flush in June and again in August through October. We conclude that the GA3 and Uni had no significant effects on the ratio of plants that initiated flowers, the nodal position of the first and final spikes, and the total number of spikes per plant in both season of spikes development in the main shoots were not clear.

Structural Changes and Fate of Crystalloplastids during Growth of Calcium Oxalate Crystal Idioblasts in Japanese Yam (Dioscorea japonica Thunb.) Tubers

The structural changes of crystalloplastids during calcium oxalate crystal idioblasts growth in Japanese yam tubers were examined by transmission electron microscopy. Idioblasts developed in the cortex of tubers during the tubers developmentwere large and elliptic and contained many crystalloplastids. The crystalloplastids were shown to have novel morphological characterizations. The single or multiple obvious electron-translucent parts without membrane structures were formed in the crystalloplastids during the crystal formation. Coincidentally, the electron-dense parts containing plastid ribosomes and tubular membranes were formed at the periphery of crystalloplastids. During further progress of crystal formation, obvious electron-translucent parts enlarged and finally electron-dense parts disappeared, forming the crystalloplastids similar to small vacuoles and/or vesicles. The majority of such crystalloplastids entered and was incorporated into the central vacuoles of idioblasts during crystal formation. The plastids remaining in the cytoplasm of mature idioblasts were proplastid-like organelle. Thus, the fate of crystalloplastids with growth of idioblasts was shown in Japanese yam tubers. It was suggested that the incorporation of crystalloplastids into central vacuoles of the idioblasts was one of the processes of material transportation involved in calcium oxalate crystal formation.

Sequence diversity in the coat protein and 3?-untranslated region of Chinese yam necrotic mosaic virus RNA

Sixteen isolates of Chinese yam necrotic mosaic virus (ChYNMV) were collected from nine sites in Japan and one site in Korea, and 1098 nucleotides of the 3″-terminal of the genome were sequenced. Identity of the coat protein gene was 95.5%–99.7% among the isolates. Substitution in the deduced amino acids of the coat protein ranged from 0 to 7, mainly in the N-terminal region. The 3″-untranslated region consisted of 231 nucleotides, which had 96.5%–100% nucleotide identity among the isolates. Sequence diversity was considerably less in ChYNMV than in Yam mosaic virus or Japanese yam mosaic virus.

Detection of Japanese yam mosaic virus by RT-LAMP

Arapid and simple procedure is described to detect the genomic RNA molecule of Japanese yam mosaic potyvirus (JYMV). This method, named RT-LAMP, allows direct detection of RNA from infected plants without careful RNA extraction, rapid thermal cycling and gel electrophoresis. RT-LAMP was successfully applied to leaves, propagules and roots of Japanese yam infected with JYMV. One of the characteristics of the RT-LAMP method is its ability to synthesize an extremely large amount of DNA. Accordingly, a large amount of by-product, pyrophospate ion, is produced yielding a white precipitate of magnesium pyrophosphate in the reaction mixture. The presence or absence of this white precipitate allows easy detection of the amplification of JYMV genomic RNA without gel electrophoresis.

Morphological Studies on the Mobilization of Reserves in Japanese Yam (Dioscorea japonica Thunb.) Seed Tuber and Eddo (Colocasia esculenta Schott var. antiquorum Hubbard & Rehder) Seed Corm on and after Sprouting

We examined the mechanism of reserve mobilization in Japanese yam seed tubers and eddo seed corms on and after sprouting. The decomposition of starch in pith parenchyma cells of Japanese yam tubers and eddo corms progressed from the region distant from vascular bundles to that adjacent to vascular bundles. In eddo corms, the starch also decomposed from the proximal to the distal region adjacent to the sprout or regenerate plant body. In the yam tubers, the decomposition process was similar in the proximal, middle and distal regions. The first step in the reserve mobilization in pith parenchyma cells was the decomposition of the amyloplast envelope. Subsequently, starch granules decomposed. In Japanese yam tubers, the envelope and starch granules started to decompose from the peripheral regions of the amyloplasts. The observation of soluble polysaccharides, which was the decomposition product of starch granules, was made possible by the quick freezing-vacuum freeze-drying method. By this method, we demonstrated that the soluble polysaccharides in the parenchyma cells decomposed and decreased in density. In addition, the mucilage in the mucilage duct started to decompose and decreased in density from the proximal to the distal part of the corm and also from the periphery to the center of the duct. It was shown that not only starch mobilization but also mucilage mobilization mainly supported sprouting and the growth of the regenerate plant body during about the first half of the vegetative stage.

Effects of Using Virus Free Plants in the Chinese Yam (Dioscorea opposita Thunb.) Cultivation and Practical Method to Distinguish a Japanese Yam Mosaic Virus Plant.

To improve productivity in the cultivation of Chinese yam 'Tanba-yamanoimo' (Dioscorea opposita Thunb.), we investigated the effect of virus free plants on the yield of a high yielding variety 'Shintanmaru' at a commercial field in 1998, 1999 and 2000. The weights of rhizophore of the virus free clone obtained from shoot apex culture were significantly heavier than infected plants with Japanese yam mosaic virus. The rates of yield increase were 27% in 1998, 17% in 1999 and 23% in 2000. The infected plants with Japanese yam mosaic virus showed the disease symptoms as mosaic in leaf, leaf transformation, leaf miniaturizing, and a delay in sprouting and growth. They could be easily distinguished from the virus free plants by their appearance. The results of distinction by symptoms in appearance and by serum test were nearly the same, with few exceptions. Because the former method was simple and not costly, it was a more effective and practical way to obtain virus free plants in seed propagation.

日本のヤマノイモから検出されるｐｏｔｙｖｉｒｕｓ

Yam mild mosaic virus (YMMV) was detected by RT-PCR from Dioscorea alata plants infected with Japanese yam mosaic virus (JYMV). The infection with YMMV was further comfirmed by nucleotide sequencing of the 3'-terminal region of the virus. RT-PCR assay for 52 D. japonica, 39 D. opposita, 9 D. alata plants with virus-like symptoms indicated that YMMV and JYMV were detected, but Yam mosaic virus was not detected from yam plants in Japan.

Complete nucleotide sequence of the genomic RNA of a mild strain of Japanese yam mosaic potyvirus.

We determined the complete nucleotide sequence of a mild strain of Japanese yam mosaic potyvirus (JYMV-M) and compared it with the published sequence of severe strain of JYMV (JYMV-J1). The genomic RNA of JYMV-M is 9,760 nucleotides (nts) in length, excluding the poly (A) tail, and encodes a polyprotein of 3,132 amino acids. Among nine potential cleavage sites, only the P1 and NIa recognition sites (between 6K1 and CI) had different sequences from those of JYMV-J1. The data confirm the strain status of these two viruses with 91.1% sequence identity for the polyprotein and approximately 94-97% identities for HC, CI, NIa, NIb and CP. The most divergent products P1 and P3 had 62% and 90% sequence identities respectively.

First Report and Molecular Characterization of Yam mild mosaic virus in Dioscorea alata on the Island of Martinique.

Naturally infected Dioscorea alata plants showing mild mosaic were collected in 1998 on the island of Martinique in the Caribbean. Isolates were first screened by double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies raised against Yam mosaic virus (YMV) and antigen-coated plate ELISA with universal potyvirus monoclonal antibodies (Agdia, Elkhart, IN). A positive reaction was obtained only with the universal potyvirus antiserum. Immunocapture reverse-transcriptase polymerase chain reaction was performed for specific detection of Yam mild mosaic virus (YMMV [3]) and YMV. A product with the predicted size of 249 bp was obtained with YMMV primers. YMMV is a recently recognized distinct potyvirus infecting D. alata in West Africa and the South Pacific (2-4). It was originally described as Yam virus I and is synonymous with Dioscorea alata virus (4). To characterize the YMMV Martinique isolate, total RNA was extracted, and universal potyvirus degenerate primers (1) were used to amplify a 700-bp fragment that included the core and C-terminal region of the coat protein (CP) and 3' untranslated region (3'UTR). Sequence information generated (EMBL AJ250336) from the cloned fragment was compared with sequences of other yam potyviruses. Sequence comparisons of the partial CP (453 nt) showed a similarity of 94.6% (amino acids [aa]) with the YMMV isolate from Papua New Guinea (EMBL AB022424 [2]); 72.2% (aa) with the Japanese yam mosaic virus (JYMV) isolate (EMBL AB016500); and 67 to 73% (aa) with 27 YMV isolates. These sequences are most diverse in the 3'UTR, which showed a similarity of 72.8% with the YMMV Papua New Guinea isolate, 30% with the JYMV isolate, and 26% with the YMV isolates. These results confirm, as previously shown by S. Fuji et al. (2), that YMMV should be classified as a new potyvirus of yam. This is the first report of the natural occurrence of YMMV in the Caribbean.

ヤマノイモモザイクウイルス弱毒系統の選抜とその強毒系統に対する干渉効果

ヤマノイモモザイクウイルス弱毒系統の選抜とその強毒系統に対する干渉効果

Nucleotide sequence of coat protein gene of yam mild mosaic virus, isolated in Papua New Guinea.

We determined the 3'-termimus 1353 nucleotides (nts) in length excluding the poly (A) tail of yam mild mosaic potyvirus (YMMV) RNA. The sequence starts within a long open reading frame (ORF) 1209 nts and is followed by untranslated region (3'-UTR) of 144 nts. The coat protein (CP) contains 266 amino acids (aa) with molecular ratio (Mr) of approximately 30 kDa. The CP of YMMV differs substantially from yam mosaic virus (YMV), Japanese yam mosaic virus (JYMV) (57 and 61% of amino acid sequence identity) and other potyvirus species. This result suggests that YMMV should be classified as a new yam potyvirus.

Complete nucleotide sequence of the genomic RNA of a Japanese yam mosaic virus, a new potyvirus in Japan.

We determined the complete nucleotide sequence of a potyvirus purified from a Japanese yam plant. The genomic RNA of this virus is 9,757 nucleotides (nts) in length, excluding the 3'-terminal poly(A) tail. It contains a single open reading frame (ORF) encoding a polyprotein of 3130 amino acids (aa) with a calculated Mr of 356,793. The genomic organization of this potyvirus is similar to that of other members of the genus Potyvirus and nine potential cleavage sites for the viral proteinase were found by comparison of its sequence with those available for other potyviruses. The nucleotide sequence and genome characteristics show that this isolate is a new potyvirus species. Its polyprotein differs substantially from Yam mosaic virus (YMV) (50% amino acid sequence identity) and fourteen other potyvirus species examined (44-59% identity). Although this potyvirus has been classified as YMV, our results suggest that the potyvirus infectious to the Japanese yam plant in Japan is distinct from YMV. Therefore, we propose that the Japanese yam potyvirus should be designated as Japanese yam mosaic virus (JYMV).

イミュノキャプチャーＰＣＲによるイチョウイモ（Ｄｉｏｓｃｏｒｅａ ｏｐｐｏｓｉｔａ Ｔｈｕｎｂ．ｃｖ．ｉｃｈｏｉｍｏ）からのヤマノイモモザイクウイルス（ＪＹＭＶ）の検出とそのＰＣＲ‐ＲＦＬＰによる強毒株と弱毒株の判別

Detection of Japanese yam mosaic potyvirus (JYMV) in Chinese yam (Dioscorea opposita Thunb. cv. ichoimo) by the immunocapture polymerase chain reaction (IC-PCR) and differentiation of virulent and attenuated isolates using restriction fragment length polymorphism (RFLP) of IC-PCR products using Tsp 509 I were investigated. JYMV was detected by IC-PCR from diseased leaves, bulbils, tubers or diseased leaves frozen at -40°C for 6 months with a sensitivity of 108, 105, 106 and 107-fold dilutions, respectively. The sensitivity of IC-PCR for the detection of JYMV from diseased leaves was about 8000-fold over ELISA and 10, 000-fold over RT-PCR. PCR-RFLP revealed different banding patterns for the virulent and attenuated isolates of JYMV. This will be useful for distinguishing virulent and attenuated isolates from Chinese yam (cv. ichoimo).

Physicochemical Property of Huaishan (Rhizoma Dioscorea) and Matai (Eleocharis dulcis) Starches

The physicochemical properties of starch, the main component in tuberous root of Huaishan (Rhizoma Dioscorea) and corm of Matai (Eleocharis dulcis) was investigated and compared with those of a Japanese yam, “Yamanoimo” starch, and potato starch. Mean particle sizes of Huaishan and Matai starches were 24 ± 5 μm and 12 ± 5 μm, respectively. X-Ray diffraction pattern suggests that Huaishan starch was B-type or C-type just close to B-type and Matai starch was A-type or C-type just close to A-type. Apparently, the intermediate component (IntCom) of Huaishan starch, which was obtained by fractionation of the starch into amylose and amylopectin, may still contain amylose and amylopectin. IntCom of Matai starch has an intermediate nature between amylose and amylopectin. It is concluded that the amylopectin molecules of Huaishan starch contain a larger amount of longer branch-ed chains and those of Matai starch contain a larger amount of shorter branched chains. Amylograms of Matai and Huaishan starches suggest that the gelatinized starches are difficult to retrograde. Digestibility of Huaishan starch by an α-amylase was the highest among the tested starches.

Electron Microscopy of Plastid-Amyloplast System Involved in Starch Synthesis and Accumulation in Japanese Yam Tuber (Dioscorea japonica).

ヤマノイモ塊茎のプラスチド - アミロプラスト系におけるデンプンの蓄積過程とその微細構造的特徴を電子顕微鏡で観察した. 走査電子顕微鏡観察によると, プラスチドは肥大が進むにつれてストロマを局在させた突出部を形成した. 内部の大部分に単粒デンプンを含むアミロプラストは, この突出部に対して垂直方向に肥大伸長した. アミロプラストの肥大停止に伴い突出部は収縮した. 透過電子顕微鏡観察によると, 突出部に局在するストロマと接するデンプン粒の表面には, 溝あるいは凹みが認められた. また, ストロマとデンプン粒の間には低電子密度の部分が観察された. これらの観察から, ヤマノイモ塊茎のアミロプラストでは, デンプンの合成とデンプン粒の形成が突出部において限定的かつ集中的に行われていると推定した. また, ヤマノイモ塊茎のプラスチドとアミロプラスト中には, デンプン粒以外にも様々な構造物が認められた. 陥入した内膜系は, ストロマ中への同化産物の輸送に効率的な構造を有していた. プラスチドのストロマには限界膜をもつ高電子密度の含有体が認められ, デンプン粒の形成は常に含有体の近傍で行われていた. また, アミロプラストのストロマ内には限界膜のない結晶構造の含有体が認められ, これらの含有体には酵素タンパク質が存在すると考えられた. また, ストロマ内に認められた顆粒状の多糖類は, 糖の一時貯蔵形態と推定された.

Identification of Endogenous Gibberellins and Abscisic Acid from Dormant Bulbils ofDioscorea japonica(Japanese Yam)

Four gibberelJins (GAs), GA19, GA20, GA24, and GA53, were identified by gas chromatography-mass spectrometry (GC-MS) from the dormant bulbils of Dioscorea japonica Thunb. ex Murray (Japanese yam), suggesting that two biosynthetic pathways of GAs, early 13- and non-13-hydroxylation pathways, are operating in the bulbils. Abscisic acid was also identified by GC-MS.

Effects of combined treatments several antagonistic plants and D-D to root-knot nematodes on Japanese yam

Effects of combined treatments several antagonistic plants and D-D to root-knot nematodes on Japanese yam