Homologies to the tomato endopolygalacturonase gene in the peach genome

Abstract. Peach endopolygalacturonase was isolated from the mesocarp tissue of soft ripe, freestone peach fruit, but was not detectable in mature pre-ripening fruit. It is a basic protein with a M_r of approximately 45000 Da, and cross-reacts with antibody to tomato endopolygalacturonase. Using a cDNA to the tomato enzyme as a probe, a fragment of peach genomic DNA was isolated which encoded about 50% of the peach enzyme. The nucleotide sequence of the fragment was determined and the amino acid sequence of part of the peach endopolygalacturonase peptide derived. Coding regions of the peach gene show extensive homology with related regions of the tomato gene. Introns are dissimilar. Endopolygalacturonase activity occurs in ripe 'freestone'peaches but not in the firmer 'clingstone'varieties. Hybridization studies identified a similar gene fragment in freestone, semi-freestone and clingstone peach varieties.     

Sensitive detection of mycoplasmalike organisms in field-collected and in vitro propagated plants of Brassica, Hydrangea and Chrysanthemum by polymerase chain reaction

A polymerase chain reaction (PCR) protocol, previously designed for amplification of a DNA fragment from aster yellows mycoplasmalike organism (MLO), was employed to investigate the detection of MLO DNA in field-collected and in vitro micropropagated plants. PCR with template DNA extracted from symptomatic, naturally-infected samples of Brassica, Chrysanthemum and Hydrangea, each yielded a DNA band corresponding to 1.0 Kbp. However, no DNA product was observed when either infected Ranunculus (with phyllody disease) or Gladiolus with (symptoms of ‘germs fins’) was used as source of template nucleic acid for PCR; further experiments indicated absence of target DNA in the case of Ranunculus and the presence of substances in Gladiolus which inhibited the PCR. The MLO-specific DNA was detected by PCR using less than 95 pg of total nucleic acid (equivalent to total nucleic acid from 1.9, ug tissue) in the case of field-collected Hydrangea and less than 11.4 pg of nucleic acid (equivalent to total nucleic acid from 19 ng of tissue) in the case of field-collected Brassica. The findings illustrate highly sensitive detection of MLOs in both field-grown and in vitro micropropagated infected plants.     

The Interplay Between Life History and Environmental Stochasticity: Implications for the Management of Exploited Lizard Populations

SYNOPSIS. The sustainable use of wild species by local peopleis emerging as an important conservation strategy. The premiseis the economic value of species will justify their own preservationas well as the habitats they occupy. However, the lack of naturalhistory and demographic information for the majority of speciesbeing exploited or with potential uses presents challengingproblems for implementing sustainable use programs. Each yearin Argentina and Paraguay, an average of 1.9 million tegu lizardsof the genus Tupinambis are exploited for their skins. In spiteof the importance of tegus as a resource, their biology is poorlyknown and their populations have never been managed. The lifehistory of Tupinambis, like that of other exploited lizards,is characterized by a relatively long life span, a large clutchsize, several years of growth before reproduction, and highmortality of hatchlings. Importantly, the mortality of young-of-the-yearand the proportion of females reproducing each year are bothprobably strongly influenced by interannual environmental variation.Whenthese parameters were randomized in life table projections tosimulate the effects of environmental stochasticity, the populationgrowth rate was highly sensitive to environmental fluctuations.Monte Carlo simulations of different harvest strategies showedthat estimates of population growth rates were overwhelminglyinfluenced by environmental variation and the number of yearsincluded in the growth rate estimate, even in the face of seeminglylarge changes in adult mortality that would result from populationmanagement. These results are both encouraging and cautionaryfor Tupinambis conservation. On the one hand these patternscan help explain how Tupinambis populations may have persistedin spite of high and variable harvest levels during many years,but conversely, stochastic effects make it difficult to evaluatethe effects of conservation measures. Size and sex can be determinedfrom harvested skins, and pilot studies suggest that analysesof the annual harvest can provide valuable information for evaluatinglong-term population trends.     

Subcellular Distribution of Inorganic Phosphate, and Levels of Nucleoside Triphosphate, in Mature Maize Roots at Low External Phosphate Concentrations: Measurements with 31P-NMR

Maize plants were grown in nutrient solution without phosphate,or in which inorganic phosphate (Pi) was maintained at nearlyconstant concentrations of 1 µM, 10µM or 0·5mM. In vivo ³¹P-NMR measurements showed that there was no discernibledifference in the cytoplasmic Pi content (µmol cm^–3root volume) of the mature roots of plants exposed to 1 µM,10µM or 0·5 mM external phosphate for up to 12d. However, the vacuolar Pi content of the mature roots variedabout 10-fold between these three groups. The cytoplasmic Pi content of roots receiving no external phosphatedecreased significantly after about 7 d total growth, and atabout this time the vacuolar pool of Pi became too small foraccurate measurement. The presence of 1 µM Pi in the nutrientsolution completely prevented this decline in cytoplasmic Pi,and there was some evidence that it also raised the Pi contentof the root vacuoles above the almost undetectable level foundin the totally P-starved roots. During the first 7–9 d of growth, the nucleoside triphosphatecontent of the mature roots was unaffected by the concentrationof phosphate in the nutrient solution. The results highlight the close control of cytoplasmic concentrationsof certain important phosphorus metabolites in roots growingin soil of normal agricultural fertility. Key words: Vacuole, cytoplasm, intracellular compartmentation, NTP, P-nutrition     

Comparative transmission of, and varietal reaction to, three isolates of rice tungro virus disease

Comparative transmission by leafhoppers of three tungro isolates obtained from the Philippines, India and Malaysia, and of an infectious clone of the Philippine isolate of rice tungro bacilliform virus (RTBV) by agroinoculation, was conducted on 12 rice cultivars. The symptoms, including height of inoculated plants were recorded and the efficiency of RTBV and rice tungro spherical virus (RTSV) transmission was determined by enzyme-linked immunosorbent assay. In most cases, the reduction of height and leaf symptoms of plants infected with RTBV and/or RTSV by the three isolates were similar in any given cultivar. On cultivar ASD 7 , the Malaysian isolate showed more severe yellow orange leaf discolouration symptoms than the Indian isolate which in turn had more severe leaf discolouration than the Philippine isolate. On the other hand, cultivars ASD 7 and Ptb 18 produced the most severe yellow orange leaf discolouration when agroinoculated with an infectious RTBV clone of the Philippine isolate. There was some variation in the transmission profile of the two tungro viruses among the three isolates. However, there was no one clear set of characteristics by which one could use cultivars to distinguish isolates. The amount of viral DNA in agroinfected plants of cultivars Utri merah, Balimau putih, Utri Rajapan and ARC 11554 was low, while the amount was high in cultivars TN1, ASD7, Ptb 18 and TKM 6. There was high correlation between the amount of viral coat protein by ELISA and viral nucleic acid by DNA hybridisation on 10 agroinoculated rice cultivars; this might indicate that similar proportions of the total RTBV DNA are encapsidated in each cultivar.