Isolation and sequence analysis of the genomic DNA fragment encoding an aspartic proteinase inhibitor homologue from potato (Solanum tuberosum L.)

A genomic DNA clone encoding an aspartic proteinase inhibitor of potato was isolated from a lambda EMBL3 phage library using the aspartic proteinase inhibitor cDNA as a hybridization probe. The gene has all characteristic sequences normally found in eucaryotic genes. Typical CAAT and TATA box sequences were found in the 5-upstream region. In this part are also two putative regulatory AGGA box sequences located. In the genomic sequence there are no intron sequences interrupting the coding region. An open reading frame of the gene encodes a precursor protein of 217 amino acids which shows high percent identity with the aspartic proteinase inhibitor cDNA.     

The use of DNA markers to estimate the extent and nature of genetic variability in Solatium tuberosum cultivars

High levels of DNA polymorphism were detected in 27 Solanum tuberosum cultivars examined. Combinations of at least two c-DNA clones have been identified which in conjunction with EcoRI allow important UK potato cultivars to be characterised by their molecular profiles. The widely grown North American cultivar Russett Burbank was also successfully fingerprinted. Estimates of genetic diversity based on restriction fragment length polymorphism (RFLP) data indicate the important role that wild potato species and exotic germplasm have played in the development of the cultivars studied. A graphical method for simultaneously highlighting similarities and differences between genotypes for individual hybridising fragments is presented. This approach is particularly useful in identifying and recording fragments which are unique to certain genotypes. Two potato cultivars: Fiona and Morag produce unique RFLP profiles when digested with EcoRI and EcoRV and probed with a flax ribosomal DNA sequence. Both Fiona and Morag possess incomplete or partial (quantitative) type resistance to G. pallida which was transferred from S. vernei. The preferential transmission of the r-DN A fragments from S. vernei may indicate that this locus is associated with genetic factors controlling resistance to G. pallida.     

Incidence and Distinguishing Characteristics of Meloidogyne chitwoodi and M. hapla in Potato from the Northwestern United States

From September 1980 to June 1981, a survey was conducted in the major potato growing regions of northern California, Idaho, Nevada, Oregon. and Washington to determine the distribution of Meloidogyne chitwoodi and other Meloidogyne spp. Meloidogyne chitwoodi and M. hapla were the only root-knot nematode species detected parasitizing potato in all the states surveyed. Meloidogyne chitwoodi occurred alone in 83% of the samples and M. hapla in 11%, with 6% of all samples containing both species. The greater incidence of M. chitwoodi, as compared to M. hapla, may be due to the cool growing season encountered in 1980 (which favored M. chitwoodi but not M. hapla) and to the increased acreage of small grains (which are good hosts for M. chitwoodi but not M. hapla) planted in rotation with potato. Differentiation between these two species can be determined by a differential host test, perineal patterns of mature females, and shape of the tail tip amt of the tail hypodermal terminus of L₂ juveniles.     

Purification and some properties of polyphenol oxidase from the yam tubers, Dioscorea bulbifera

In a comparison of the polyphenol oxidase activity of various species of yam tubers the greatest enzyme activity was found in D. bulbifera. The enzyme was purified from acetone powder extracts of this plant. Ammonium sulphate fractionation, followed by ion exchange chromatography and gel filtration gave 22-fold purification. The final product gave a single band on polyacrylamide disc gel electrophoresis. The purified enzyme showed activity towards catechol, pyrogallol and dl-β-3,4-dihydroxyphenylalanine (dl-DOPA) and had a MW 115000 ± 2000. It was characterized by response to various inhibitors. β-Mercaptoethanol, dithioerythritol, l-cysteine, sodium metabisulphite and KCN inhibited strongly.     

Biochemical mechanism for the inhibition of phenylalanine ammonia-lyase induction in the absence of oxygen in potato tuber tissue

Induction of phenylalanine ammonia-lyase (PAL) in excised potato parenchyma tissue in the presence of light displayed a rigid requirement for oxygen. A     

Description and SEM Observations of Meloidogyne chitwoodi n. sp. (Meloidogynidae), a Root-knot Nematode on Potato in the Pacific Northwest

Meloidogyne chitwoodi n. sp. is described and illustrated from potato (Solanum tuberosum) originally collected from Quincy, Washington, USA. This new species resembles M. hapla, but its perineal pattern is basically round to oval with distinctive and broken, curled, or twisted striae around and above the anal area. The vulva is in a sunken area devoid of striae. Vesicles or vesicle-like structures are present in the median bulb of females. The larva tail, being short and blunt with a hyaline tail terminal having little or no taper to its rounded terminus, is distinctively different from M. hapla. SEM observations revealed the nature of the perineal pattern and details of the head of larvae and males, and showed the spicules to have dentate tips ventrally. Hosts for M. chitwoodi n. sp. include potato, tomato, corn, and wheat but not strawberry, pepper, or peanut. The latter three crops are excellent hosts for M. hapla. The known distribntion of this new root-knot species presently involves certain areas of Idaho, Washington, and Oregon. The common name "Columbia root-knot nematode" is proposed for M. chitwoodi n. sp.     

Chymotrypsin inhibitor from potatoes: interaction with target enzymes

The interactions of chymotrypsin, subtilisin and trypsin with a low MW proteinase inhibitor from potatoes were investigated. The K_i value calculated for the binding of inhibitor to chymotrypsin was 1.6 ± 0.9 × 10^?10M, while the second-order rate constant for association was 6 × 10⁵ M^?1/sec. Although binding was not observed to chymotrypsin which had been treated with diisopropyl fluorophosphate or with l-tosylamide-2-phenylethyl chloromethyl ketone, the 3-methylhistidine-57 derivative bound inhibitor with a K_i value of 9.6 × 10^?9 M. The inhibitor also exhibited a tight association with subtilisin (K_i < 4 × 10^?9 M). In contrast, little inhibition of trypsin was observed, and this was believed to be due to low levels of a contaminant in our preparations. No evidence for reactive site cleavage was observed after incubation of the inhibitor with catalytic amounts of chymotrypsin or subtilisin at acid pH.     

Two phytoalexin glycosides from potato tubers infected with Phoma

Four coumarins and seven isoprenoid compounds have been identified in potato tubers infected with Phoma exigua var. foveata. Among these were the 7-O-β-D-glucopyranoside of 7-hydroxy-6,8-dimethoxycoumarin (isofraxidin) and the sesquiterpene 2-(11,12-dihydroxy-11-methylethyl)-6,10-dimethyl-spiro[4,5]dec-6-en-8-one and its 12-O-β-D-glucopyranoside, which apparently have not been previously identified in potato tubers. At least two diastereoisomers of the latter glucoside were present. Analysis of eight fluorescent compounds in different parts of infected potatoes was performed by an improved HPLC technique.     

Carbohydrate metabolism during cold-induced sweetening of potato tubers

The aim of this work was to discover the effects of lowering the temperature from 25° to 2° on the metabolism of glucose [U-¹⁴C] by tubers of Solanum tuberosum. Isotope was applied to tubers via a 50-μl hole made with a capillary pipette. Tubers were incubated for 2 hr, the pulse; then the glucose- [U-¹⁴C] was replaced with glucose, and incubation was continued for 18 hr, the chase. The detailed distribution of ¹⁴C was determined at the end of the pulse and at the end of the chase at 2°, and compared with those found at 25°. Lowering the temperature reduced the proportion of metabolized ¹⁴C that entered the respiratory pathways. At 2°, but not at 25°, hexose phosphates were the most heavily labelled fraction after the pulse: during the chase at 2° much of this label was metabolized to sucrose. We conclude that lowering the temperature preferentially restricts glycolysis and diverts hexose phosphates to sucrose. We suggest that this is an important cause of cold-inducing sweetening of the tubers and is due to cold-lability of key glycolytic enzymes.