Isolation of a Specific Potato Tuber-Inducing Substance from Potato Leaves

Potato tuberization is induced by an unidentified "tuberizationstimulus" which is produced in the leaves. Recently, we confirmedthe occurrence of two acidic substances in the leaves whichappear to be the stimulus (Koda and Okazawa 1988). We reporthere the isolation of one of the substances from potato leaves.The molecular weight of the substance is 388. The substanceis active in inducing tuberization in vitro at a concentrationof 0.01 mg- liter^-11 (ca. 3 ? 10^-8 M). (Received April 15, 1988; Accepted June 28, 1988)     

Chemotherapeutical Elimination of Potato Virus X from Potato Stem Cuttings

Potato virus X was completely eliminated from all infected potato stem cuttings grown in nutrient media containing 0.02 or 0.03 % 2,4-dioxohexahydro-1,3,5-triazine (DHT). When DHT was added to the media in concentrations of 0.01 and 0.005% the efficiency by which the virus was eliminated differed between the varieties tested. The method is less time-consuming than the generally used meristem (axillary-) tip culture in combination with chemo- or thermotherapy.     

Potato phosphorylase isoenzymes

Potato phosphorylase isoenzymes were separated by gel electrophoresis, and DEAE-Sephadex chromatography. Electrofocusing experiments showed a heterogeneity in isolelectric point. Molecular weights and Stokes-radii were estimated using Sephadex G200. The adsorption on glycogen of two low molecular weight forms, probably dimers, was investigated by means of gel electrophoresis. The dissociation constants were 5 × 10⁻⁵ and 2 × 10⁻³% glycogen.     

Detection of Potato Tuber-Inducing Activity in Potato Leaves and Old Tubers

Potato tuberization is induced under short days but substancewhich triggers it is still unknown. Tuber-inducing activitywas detected in leaves and old tubers using single-node stemsegment culture in vitro as a bioassay method. The activityin leaves increased under short days, but remained almost constantunder long days. It was also found in physiologically old tubers.Anion exchange chromatography of the ethanol extract gave aneluate that exhibited strong tuber-inducing activity. Partialpurification revealed the presence of two kinds of active substances,one of which seemed to be a glycoside of the other. These substancesappear to be different from known plant hormones. (Received October 19, 1987; Accepted June 9, 1988)     

Biochemical Effects of Gamma Radiation on Potato and Sweet Potato Tissues

Relationship between the chemical constituents of tobacco leaves and the gaseous constituents of cigarette smoke from which K value¹⁾ was computed was discussed and the following presuppositions were demonstrated to be correct.

1. Fibrous substances in tobacco leaves are the main precursors of acetaldehyde, propionaldehyde, acrolein, acetone, methylethylketone, diacetyl, methanol, furan, an unknown compound, No. 6 and an unknown compound, No. 16 in cigarette smoke.

2. Sugars in tobacco leaves are the main precursors of 2-methylfuran and 2,5-dimethyl- furan in cigarette smoke.

3. Resinous substances in tobacco leaves are the main precursors of isoprene and an unknown compound, No. 2 in cigarette smoke.

     

Expression of Potato Virus Y Coat Protein Gene in Transgenic Potato

Potato virus Y (PVY) N coat protein (CP) coding sequence was cloned into a plant expression vector pMON316 under the CaMV 35S promoter. Leaf discs of potato (Solanum tuberosum) were used to Agrobacterium-mediated gene transfer. A large number of regenerated putative transgenic plants were obtained based on kanamycin resistance. Using total DNA purified from transgenic plants as templates and two oligonucleotides synthesized from 5' and 3' of the PVY coat protein gene as primers, the authors carried out polymerase chain reaction (PCR) to check the presence of this gene and obtained a 0. 8 kb specific DNA fragment after 35 cycles of amplification. Southern blot indicated that the PCR product was indeed PVY CP gene which had been integrated into the potato genome. Enzyme-linked immunosorbent assay (ELISA) of our transgenic plants showed that CP gene was expressed in at least some transgenic potato plants.     

马铃薯卷叶病毒基因间隔区转化的马铃薯抗病性研究

将本室合成、克隆的马铃薯卷叶病毒（ＰｏｔａｔｏＬｅａｆｒｏｌＶｉｒｕｓ,ＰＬＲＶ）中国分离株的基因间隔区（ｉｎｔｅｒｇｅｎｉｃｓｅｑｕｅｎｃｅ,ＩＳ）双链ｃＤＮＡ以正、反向两种方式分别构建于转化载体ｐＲＯＫ２中,通过致瘤农杆菌介导,以马铃薯叶圆片为转化材料,转化马铃薯栽培品种Ｄｅｓｉｒｅ,获得了转基因植株。卡那霉素抗性分析和ＰＣＲ检测目的基因,证明ＰＬＲＶＩＳ双链ｃＤＮＡ已经整合到转基因马铃薯的染色体基因组中。将转基因植株移栽网棚用蚜虫接种ＰＬＲＶ,观察症状并用酶联免疫吸附测定（ＥＬＩＳＡ）检测转基因植株中ＰＬＲＶ含量。结果表明,表达ＰＬＲＶＩＳ正意和反意ＲＮＡ的转基因植株,接种病毒后表现无症状或症状轻微,ＰＬＲＶ平均滴度均较未转基因对照植株低。表达正意ＲＮＡ的转基因植株ＰＬＲＶ滴度降低４３％～７２％,表达反意ＲＮＡ的转基因植株ＰＬＲＶ滴度降低７２％～８６％,由此可见,表达ＰＬＲＶＩＳ反意ＲＮＡ的转基因马铃薯对ＰＬＲＶ抗性较强。     

马铃薯卷叶病毒基因间隔区转化的马铃薯抗病性研究

将本室合成、克隆的马铃薯卷叶病毒(Potato Leafroll Virus, PLRV)中国分离株的基因间隔区(intergenic sequence, IS)双链cDNA以正、反向两种方式分别构建于转化载体pROK2中,通过致瘤农杆菌介导,以马铃薯叶圆片为转化材料,转化马铃薯栽培品种Desiree,获得了转基因植株.卡那霉素抗性分析和PCR检测目的基因,证明PLRV IS双链cDNA已经整合到转基因马铃薯的染色体基因组中.将转基因植株移栽网棚用蚜虫接种PLRV,观察症状并用酶联免疫吸附测定(ELISA)检测转基因植株中PLRV含量.结果表明,表达PLRV IS正意和反意RNA的转基因植株,接种病毒后表现无症状或症状轻微,PLRV平均滴度均较未转基因对照植株低.表达正意RNA的转基因植株PLRV滴度降低43%～72%,表达反意RNA的转基因植株PLRV滴度降低72%～86%,由此可见,表达PLRV IS反意RNA的转基因马铃薯对PLRV抗性较强.     

Somatic Hybridization of Dihaploid Potato Protoplasts as a Tool for Potato Breeding*

Using electrofusion of protoplasts from different dihaploid potato breeding clones, 308 somatic hybrids, i.e. 16.7% of the totally regenerated plants, were obtained. The results indicate that factors such as ‘combining ability’ strongly influence hybrid formation in these intraspecific fusion experiments. Hybrid identification was predominantly carried out by isoenzyme analysis of the peroxidases and/or esterases in polyacrylamide-gradient gel electrophoresis. Further confirmation of the hybrid character was obtained by scoring phenotypic markers (petal colour, stem anthocyanin production, tuber characteristics, etc.) and, in some combinations, by evaluating tolerance against the herbicide metribuzin and nematode resistance against Globodera rostochiensis (Ro 1). The successful inheritance of metribuzin tolerance and nematode resistance confirm that monogenic dominant inherited traits are combined in the hybrids.     

马铃薯Y病毒蚜传辅助因子促进马铃薯X病毒长距离运输

采用PCR和定点突变法,对马铃薯Y病毒中国株系（Chyinese strain of potato Ypotyvirus,PVY-C)蚜传辅助成分（helper component proteinase,HC-Pro)基因中心区域的CCCT基序和PTK基序进行定点改造,获得了4种突变体。然后将突变体砍降到植物表达载体pBin438中,所得到的重组体通过根癌土壤杆菌（Agrobacterium tumefaciens(Smith et Townsend)Conn）介导法转了烟草（Nicotiana tabacum L.cv.K326).Southern blotting和Western blotting分析表明4种突变体已经成功整合到烟草的基因组中,并在蛋白水平上得到了表达。马铃薯X病毒（potato X potexvirus,PVX)对转基因烟草的攻毒实验表明,4种突变体均使PVY－C HYC－Prog严重丧失了促进PVX病毒粒子在寄主体内积累和提高PVX致病性的功能,说明CCCT、PTK基序为PVY－C HYC－Pro介导PVX／PVY协生作用所必需。同时证明了HC-Pro具有增强PVX在寄主体内长距离运输的功能。     

Functionally Homologous Host Components Recognize Potato Virus X in Gomphrena globosa and Potato

All known isolates of potato virus X (PVX), with the exception of a South American isolate PVXHB, induce an extreme resistance response on potato carrying the Rx gene and elicit the production of necrotic lesions on Gomphrena globosa: PVXHB establishes systemic infection on Rx genotypes of potato and infects the inoculated leaf of G. globosa without lesion formation. Previously, we have shown that the Rx-mediated resistance is affected by a feature of the coat protein that depends on the presence of a threonine residue at position 121 in the coat protein of PVXCP4 and that the resistance is an induced response expressed in protoplasts of potato with the Rx genotype. In this study, we provide evidence, based on the analysis of PVXCP4/PVXHB hybrids, that the elicitation of lesions on G. globosa also requires the presence of a threonine residue at position 121 of the viral coat protein. The lesion-forming phenotype was not associated with the ability of the viral isolate to accumulate in the infected plant. We therefore propose that there is a homologous component of both potato carrying Rx and G. globosa that interacts with a feature of the PVX coat protein and, following the interaction, activates an induced response in the plant cell.     

Isolation, Crystallization, and Partial Identification of Potato Factor II from Potato Tubers

The isolation, crystallization, and partial identification of potato factor II, a stimulator from the chemically neutral fraction of potato extract, is described. The compound was originally found to stimulate elongation of dwarf peas grown under red light, a gibberellin bioassay. It melts between 137° and 139°. In paper chromatography it migrates to R_F 0.62 in isopropyl alcohol: ammonium hydroxide: H₂O (10:1:1, v/v). Based on infrared and NMR data, it does not contain a lactone ring and possibly possesses an amide radical and an OH⁻ group, as well as many methylene radicals. Potato factor II may be similar to certain of the fatty acid derivatives previously reported to stimulate growth of excised sections, but it is unique in that it stimulates growth of intact plants. This effect points to the need for completely separating neutral from acid gibberellin-like substances when the latter are assayed on dwarf peas.