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PubMed2002

Repression of stress-responsive genes by FIERY2, a novel transcriptional regulator in Arabidopsis.

Low temperature, drought, and high salinity induce the expression of many plant genes. To understand the mechanisms for the transcriptional activation of these genes, we conducted a reporter gene-aided genetic screen in Arabidopsis. Seven allelic mutations in the FIERY2 (FRY2) locus result in significant increases in the expression of stress-responsive genes with the DRE/CRT (drought-responsive/C-repeat) cis element but non-DRE/CRT type stress-responsive genes were less affected. The specific regulation of DRE/CRT class of genes by FRY2 appears to be caused by repression of stress induction of the upstream CBF/DREB transcription factor genes. fry2 mutants show increased tolerance to salt stress and to abscisic acid during seed germination but are more sensitive to freezing damage at the seedling stage. FRY2/CPL1 encodes a novel transcriptional repressor harboring two double-stranded RNA-binding domains and a region homologous to the catalytic domain of RNA polymerase II C-terminal domain phosphatases found in yeast and in animals that regulate gene transcription. These data indicate that FRY2 is an important negative regulator of stress gene transcription and suggest that structured RNA may regulate hormone and stress responses in plants as it does in animals.

Abscisic Acid↗
PubMed1992

Contrasting leaf phenotypes control seasonal variation in water loss in a tropical forest shrub.

Psychotria marginata, a shrub common to humid tropical forests in Central America, produces leaves in two seasonal flushes with contrasting morphology and physiology. Leaf production is bimodal with a major peak at the beginning of the annual wet season and a secondary peak at the end of the wet season. Together these peaks account for 75-87% of annual leaf production. Leaves produced just prior to the dry season have higher specific mass and, during drought, have lower stomatal conductances and higher water-use efficiencies. Plants irrigated during two consecutive dry seasons continued to produce leaves with these morphological and physiological differences, indicating that this feature has been strongly canalized by some factor other than water availability in this highly predictable yet seasonal habitat. The bimodal leaf production results in acclimation to changing conditions through co-occurring leaves that lack the physiological plasticity usually associated with acclimation. Heterophylly of this form suggests that the moderate drought of the dry season has been a significant selective factor for understory plants.

Journal Article↗
PubMed1999

A highly conserved kinase is an essential component for stress tolerance in yeast and plant cells.

Osmotic stress (drought, salt stress) is a major limiting factor for crop productivity in the world. Because cellular responses to osmotic stress are thought to be conserved in eukaryotes and because yeast is much more amenable than plants to genetic research, a functional strategy has been performed to identify limiting steps in osmotolerance of plants based on the complementation of yeast with a plant library. A new plant cDNA that encodes a functional homologue of the yeast Dbf2 kinase enhances salt, drought, cold, and heat tolerance upon overexpression in yeast as well as in transgenic plant cells.

Amino Acid Sequence↗
PubMed2003

Fructans in crested wheatgrass leaves.

Crested wheatgrass is an important cool-season grass that has become naturalized in many semiarid regions of the western U.S. It provides ground cover and reduces soil erosion caused by water and wind. Additionally, crested wheatgrass produces important forage for livestock and wildlife on 6 to 8 million hectars of western rangeland. It is well adapted to semiarid cold desert regions because of its cool temperature growth and drought tolerance. Understanding the biosynthesis of fructans in crested wheatgrass is important because of their likely role in both cool temperature growth and drought tolerance. Recent research described a major gene (6-SFT) in crested wheatgrass that is involved in fructan biosynthesis. 1-kestotriose, the major DP3 fructan in crested wheatgrass, serves as the substrate for the two major DP4 fructans, 1&6-kestotetraose and 1,1-kestotetraose. The three major DP5 fructans are 1&6,1-kestopentaose, 1,1&6-kestopentaose and 1,1,1-kestopentaose. The major DP6 fructan is 1&6, 1&6-kestohexaose. We postulate that 1&6,1&6-kestohexaose is synthesized from the addition of a fructose to 1&6, 1-kestopentaose. This paper provides structures of the various DP 3, 4, 5 and 6 fructan types produced by crested wheatgrass and provides suggested biosynthetic pathways for all major fructan linkage types present.

Agropyron↗
PubMed2006

Women's input into household decisions and their nutritional status in three resource-constrained settings.

OBJECTIVE: To understand the role of women's input into household decisions as a possible factor contributing to women's undernutrition in settings where HIV/AIDS and drought have constrained household resources. DESIGN AND SETTING: Three cross-sectional surveys of non-pregnant women in partnerships without a birth in the last 3 months were analysed. Factors associated with chronic energy deficiency (CED), defined as body mass index of<18.5 kg m(-2), were assessed among 1920 women in Zimbabwe, 2870 women in Zambia and 6219 women in Malawi. RESULTS: Prevalence of CED was 4.2% in Zimbabwe, 13.5% in Zambia and 6.7% in Malawi. In Malawi, women with less input into decisions were more likely to have CED. After multivariable adjustment, each additional decision made by the partner increased the odds of CED in Malawi by 1.08 (95% confidence interval (CI) 1.02-1.15); each additional decision made by the woman decreased the odds of CED by 0.90 (95% CI 0.88-0.97). Malawian women with all the final say or with partners with no final say had significantly more CED than expected (odds ratio (OR)=2.88, 95% CI 1.42-5.83 and OR=1.64, 95% CI 1.06-2.52, respectively), and removing these points increased the magnitude and significance of the linear trends. In Zambia, the relationship was found for urban women only and no associations were found in Zimbabwe. CONCLUSIONS: Input into household decisions may be a key factor in the cycle of drought and CED. Women with both low input and CED may lose productive capacity, putting them at greater risk of food insecurity and potentially HIV/AIDS in high prevalence settings.

Adolescent↗
PubMed1977

Preliminary trials against Biomphalaria glabrata of a new molluscicide formulation: geletin granules containing Bayluscide wettable powder.

Tests were conducted with gelatin granules containing Bayluscide (niclosamide) w.p., 23-3% w/w a.i. Granules rendered a simulated field habitat (banana drain) lethal to Biomphalaria glabrata for 40 days when applied at a rate calculated to give 5 mg/1 in the water. At this dose, Bayluscide e.c. was effective for 8-12 days. Granules exposed to various combinations of natural or simulated tropical climatic factors for up to 56 days gave variable kills of snails, apparently unrelated to the factors tested. The rate at which the molluscicide was released from the granules was affected by climatic factors: high temperatures and low humidities slowed the rate, probably by hardening the granules; rainfall and high humidities accelerated the rate, probably by softening or disintegrating the granules. There was no apparent loss of molluscicidal activity in granules exposed for 56 days to various combinations of climatic factors. The results suggest that this formulation may be applied during droughts to temporary habitats when these are dry and accessible. The molluscicide would then be released at the unpredictable start of the next wet season and kill any snails which survive the drought by aestivation.

Animals↗
PubMed1990

Hydatid disease in the Turkana District of Kenya, VII: analysis of the infection pressure between definitive and intermediate hosts of Echinococcus granulosus, 1979-1988.

The rate of acquisition of Echinococcus granulosus and Taenia hydatigena was examined in dogs treated with praziquantel in northwestern Turkana District of Kenya. An attempt was also made to assess the effect of drought on the prevalence of E. granulosus. The infection pressure to dogs with the cestodes was shown to be high, and the prevalence returned to pretreatment levels within six months. The unreliability of arecoline purging in prevalence studies of dog cestodes is shown by mathematical contrast to the results of autopsy. Arecoline purge may underestimate the real prevalence by 10-fold. Dosing intervals in hydatid control programmes utilizing mass dog-purging to estimate re-infection rates should therefore take this factor into consideration. It is proposed that a mass dog-dosing schedule in Turkana, using praziquantel, should take into consideration the short prepatent period of E. granulosus, the financial constraints, and the slaughter practices in the area. During the prolonged droughts which occur approximately every 10 years, the programme will be adjusted accordingly to cater for the initial increase in infection intensity to dogs.

Animals↗
PubMed1989

A survey of the phosphorus and calcium contents of pastures and the serum inorganic phosphorus and calcium contents of cows on four Manawatu dairy farms.

Serum inorganic phosphorus (Pi) and calcium (Ca) concentrations were assessed in 20 cows on each of four Manawatu factory supply dairy farms. Blood was taken from each cow before calving and at six-week intervals during lactation. Bleeding coincided with herd testing. Herds of Friesian or Friesian X cows and Jersey or Jersey X cows were compared on adjacent farms on a Central Yellow-brown Sand and on adjacent farms on a Peat Loam overlying a Central Yellow-brown Earth soil. Pasture mass and composition were estimated to grazing height in the next two paddocks to be grazed in the rotation. Mean serum Pi concentration was higher in cows on sandy soils (1.55 mmol Pi/l than in cows on the peat loam (1.34 mmol Pi/l (P<0.001). Concentrations were highest before calving (1.69 mmol Pi/l) but fell to low levels at peak lactation (1.17mmol Pi/l when 70% of cows were below the minima of the 'normal range', and during the drought (1.29 mmol Pi/l. Pasture phosphorus (P) concentrations were adequate to support cow nutrition for lactation (>0.33% DM, ad lib. feeding) until the summer drought when low herbage mass would have restricted milk production. Serum Ca was adequate for lactating cows and changed little between months or between cows (mean 2.12 mmol Ca/l). No metabolic disorders relating to mineral deficiencies were observed. It appears that serum Pi in a high proportion of cows falls below the normal range during peak lactation without cows displaying clinical deficiency symptoms or a depression in butterfat production.

Journal Article↗
PubMed2005

Genotypic variability for carbon isotope discrimination in the mutant and improved lines of barley.

Drought tolerance is an important breeding objective in dry and semi-dry conditions. Carbon isotope discrimination (Delta) is a tool that may be used to improve water-use efficiency (WUE) as an indirect selection criterion. The study investigated the variability for Delta in improved F7 lines and their parents (three cultivars and two mutant lines), which were sampled randomly from an F6 nursery performing well under semi-dry conditions. In total, 40 entries were grown in sand culture, arranged in three-replicated randomized complete block designs in two sets of experiments in Antalya, Turkey. There were statistically significant differences (p<0.01) among genotypes in both sets of experiments for Delta, and Delta values range from 20.14 to 21.86. Low coefficient of variation (C.V.) values, i.e. 2 and 1.65 %, for both data sets revealed efficient control of experimental error for Delta and indicated little effect of environment. Consequently, broad-sense heritability estimates for Delta were 0.63 and 0.74. As Delta showed a considerably high heritability and consistency over the two sets of experiments and low C.V. values, it was concluded that this trait could be used in breeding programmes aimed at developing drought tolerance lines. The early heading mutant, M-K-88, and the cultivar selected from land race, Tokak 157-37, showed lowest Delta values, indicating that they had the best water-use efficiency. Low Delta values of these two genotypes were inheritable.

Carbon Isotopes↗
PubMed2005

Molecular cloning and characterization of a dehydration-inducible cDNA encoding a putative 9-cis-epoxycarotenoid dioxygenase in Arachis hygogaea L.

A rate-limiting step in abscisic acid (ABA) biosynthesis in plants is catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). Here we present the cloning, characterization of a cDNA from dehydrated peanut (Arachis hygogaea L.) leaves that encodes a putative NCED. The 2486-bp full-length cDNA (designated as AhNCED1), obtained by rapid amplification of cDNA ends (RACE), has an open reading frame of 601 amino acid residues and encodes a protein with a calculated molecular weight of 66.86 kDa and an isoelectric point of 8.39. Sequence analysis shows that the deduced amino acid sequence of AhNCED1 shares high identity with the reported NCED protein sequences. There is a 30-amino-acid chloroplast-targeting peptide at the N-terminus of the AhNCED1 protein predicted by iPSORT algorithm. Semi-quantification by duplex RT-PCR reveals that the expression of AhNCED1 is up-regulated by dehydration and that rehydration represses its expression. The organ specific expression pattern of AhNCED1 has been examined, which indicates its dominant expression in leaves and stems. Molecular analysis of the drought-inducible gene of peanut may be useful to investigate the response of agricultural crops to drought stress.

Amino Acid Sequence↗
PubMedDate not supplied

Vulnerability of waterborne diseases to climate change in Canada: a review.

This project addresses two important issues relevant to the health of Canadians: the risk of waterborne illness and the health impacts of global climate change. The Canadian health burden from waterborne illness is unknown, although it presumably accounts for a significant proportion of enteric illness. Recently, large outbreaks with severe consequences produced by E. coli O157:H7 and Cryptosporidium have alarmed Canadians and brought demands for political action. A concurrent need to understand the health impacts of global climate changes and to develop strategies to prevent or prepare for these has also been recognized. There is mounting evidence that weather is often a factor in triggering waterborne disease outbreaks. A recent study of precipitation and waterborne illness in the United States found that more than half the waterborne disease outbreaks in the United States during the last half century followed a period of extreme rainfall. Projections of international global climate change scenarios suggest that, under conditions of global warming most of Canada may expect longer summers, milder winters, increased summer drought, and more extreme precipitation. Excess precipitation, floods, high temperatures, and drought could affect the risk of waterborne illness in Canada. The existing scientific information regarding most weather-related adverse health impacts and on the impacts of global climate change on health in Canada is insufficient for informed decision making. The results of this project address this need through the investigation of the complex systemic interrelationships between disease incidence, weather parameters, and water quality and quantity, and by projecting the potential impact of global climate change on those relationships.

Animals↗
PubMed1999

Environmental imperatives reconsidered: demographic crises in western North America during the medieval climatic anomaly.

Review of late Holocene paleoenvironmental and cultural sequences from four regions of western North America show striking correlations between drought and changes in subsistence, population, exchange, health, and interpersonal violence during the Medieval Climatic Anomaly (A.D. 800-1350). While ultimate causality is difficult to identify in the archaeological record, synchrony of the environmental and cultural changes and the negative character of many human responses--increased interpersonal violence, deterioration of long-distance exchange relationships, and regional abandonments--suggest widespread demographic crises caused by decreased environmental productivity. The medieval droughts occurred at a unique juncture in the demographic history of western North America when unusually large populations of both hunter-gathers and agriculturalists had evolved highly intensified economies that put them in unprecedented ecological jeopardy. Long-term patterns in the archaeological record are inconsistent with the predicted outcomes of simple adaptation or continuous economic intensification, suggesting that in this instance environmental dynamics played a major role in cultural transformations across a wide expanse of western North America among groups with diverse subsistence strategies. These events suggest that environment should not be overlooked as a potential cause of prehistoric culture change.

Climate↗
PubMed1975

An ecological comparison of the two arid-zone kangaroos of Australia, and their anomalous prosperity since the introduction of ruminant stock to their environment.

This paper discusses the interactions between the large and medium-sized marsupials, the introduced ruminant domestic stock, and the environment in the arid zone of Australia. The grazing of sheep and cattle has produced suitable subclimax pastures which today favor two sympatric kangaroos but not the smaller bandicoots and wallabies. Tall grass tussocks used as shelter by the latter have been grazed down by the ruminants, and replaced by "marsupial lawns" or xeric spinifex, depending on locality, thereby improving the food supplies for the plains kangaroo and the hill kangaroo, respectively. It is argued, however, that even these smaller marsupials benefited originally from the new grazing regime. Patchy grazing of the grasslands probably created edge effects and other early seral changes which improved the food supplies while leaving adequate shelter. Continued grazing by increasingly large numbers of sheep and cattle ultimately and critically removed the shelter and, therefore, eliminated the bandicoots and wallabies. There is evidence that the plains kangaroo, though generally abundant at the present time, is vulnerable to competitive displacement by sheep, cattle, rabbits, and, in one region, by the hill kangaroo when it invades the plains. The plains kangaroo with its diet of green herbage is most threatened during droughts because the other herbivores have finer-grained diets. Like the bandicoots and wallabies the plains kangaroo in at least two localities appears to have first increased in numbers and then decreased. Sheep and cattle numbers have generally done the same. It is postulated, therefore, that there may not be two opposing response curves for the large and medium-sized marsupials to the ruminant invasion of the inland plains, but, in the long run, only one: an initial numerical increase and then decline. Only the time-scale is different, taking 50 years or more for the plains kangaroo, but perhaps half that time or less for the bandicoots and wallabies. The hill kangaroo may be the ultimate winner because it requires the least nitrogen, and the spinifex it eats during drought has spread as part of the subclimax created by ruminants.

Adaptation, Biological↗
PubMed2005

Endogenous nitrogen excretion by red kangaroos (Macropus rufus): effects of animal age and forage quality.

Red kangaroos (Macropus rufus) are large (>20 kg) herbivorous marsupials common to arid and semiarid Australia. The population dynamics of red kangaroos are linked with environmental factors, operating largely through juvenile survival. A crucial period is the young-at-foot (YAF) stage, when juveniles have permanently left the mother's pouch but still take milk from a teat in the pouch. Forage quantity and quality have been implicated in drought-related mortalities of juvenile kangaroos. Here we compared how forage quality affected nitrogen (N) intake and excretion by YAF, weaned, and mature, nonlactating female red kangaroos. On high-quality forage (chopped lucerne hay, Medicago sativa) low in neutral-detergent fiber (43%+/-1%) and high in N (2.9%+/-0.1%), YAF and weaned kangaroos had ideal growth rates and retained 460-570 mg dietary N kg(-0.75) d(-1). But on poor-quality forage (chopped oaten hay, Avena sativa) high in neutral-detergent fiber (64%+/-1%) and low in N (0.9%+/-0.1%), YAF and weaned kangaroos could not sustain growth and were in negative N balance at -103+/-26 mg and -57+/-31 mg N kg(-0.75) d(-1), respectively. Notably, the YAF kangaroos excreted 64% of their truly digestible N intake from forage as nondietary fecal N (NDFN). By weaning age, the situation had improved, but the juveniles still lost 40% of their truly digestible N intake as NDFN compared with only 30% by the mature females. Our findings support field observations that forage quality, and not just quantity, is a major factor affecting the mortality of juvenile red kangaroos during drought.

Aging↗
PubMed1978

Nutritional success in a semi-arid land: examination of Tswana agro-pastoralists of the eastern Kalahari, Botswana.

The cultural and environmental factors affecting the food quest and nutritional status of the Moshaweng Tlokwa, a Tswana agro-pastoral society occupying the semi-arid eastern Kalahari Desert of Botswana, are examined. Data are presented on methods of food procurement, storage, preparation, and preservation. Tlokwa diet is based on agriculture horticulture and animal husbandry but a surprising number of wild species are regularly used as food. This pattern is nutritionally protective and viewed by the author as a principal reason for Tlokwa dietary success in their semi-arid environment. Data are presented on food habits, dietary prohibitions, and characteristic diets of infants, children, adolescents, and adults. Many Tlokwa foods are encouraged or prohibited on the basis of the consumers age, sex, and social development. Such patterns reduce competition for dietary resources, assure a more equitable distribution of food, and sustain the nutritional quality of diet. During 1973 to 1975 the Tlokwa appeared healthy and well fed; heavy rain-fall had just broken a 7-year drought. Kwashiorkormarasmus, avitaminosis, or other classical signs of malnutrition were not observed. A trend towards bottle feeding was noted. Children and adolescents are rapidly losing their ability to identify edible wild food resources. The author concludes that the Tlokwa heretofore have coped satisfactorily with drought in their semi-arid territory and recommends continued diversification of their food quest. Diversity is viewed as essential if the Tlokwa are to maintain their nutritional well-being in coming decades.

Adolescent↗
PubMed2000

Phenotypic responses of wild barley to experimentally imposed water stress.

Responses to water stress within a population of wild barley from Tabigha, Israel, were examined. The population's distribution spans two soil types: Terra Rossa (TR) and Basalt (B). Seeds were collected from plants along a 100 m transect; 24 genotypes were sampled from TR and 28 from B. Due to different soil water-holding capacities, plants growing on TR naturally experience more intense drought than plants growing on B. In a glasshouse experiment, water was withheld from plants for two periods (10 d and 14 d) after flag leaf emergence. A total of 15 agronomic, morphological, developmental, and fertility related traits were examined by analysis of variance (ANOVA). Ten of these traits were significantly affected by the treatment. A high degree of phenotypic variation was found in the population with significant genotypextreatment and soil typextreatment interactions. Principal component analysis (PCA) was performed using combined control and stress treatment data sets. The first three principal components (pc) explained 88.8% of the variation existing in the population with pc1 (47.9%) comprising yield-related and morphological traits, pc2 (22.9%) developmental characteristics and pc3 (18.0%) fertility-related traits. The relative performance of individual genotypes was determined and water stress tolerant genotypes identified. TR genotypes were significantly less affected by the imposed water stress than B genotypes. Moreover, TR genotypes showed accelerated development under water deficit conditions. Data indicate that specific genotypes demonstrating differential responses may be useful for comparative physiological studies, and that TR genotypes exhibiting yield stability may have value for breeding barley better adapted to drought.

Adaptation, Physiological↗
PubMed2001

Hydraulic vulnerability, vessel refilling, and seasonal courses of stem water potential of Sorbus aucuparia L. and Sambucus nigra L.

Differences in the seasonal variation in stem water potential between the two shrub species Sorbus aucuparia and Sambucus nigra were related with their vulnerability to xylem cavitation. It was also demonstrated indirectly that the two species differ in the extent to which they reverse cavitation. Seasonal variation in stem water potential was investigated during three growing seasons with in situ stem psychrometers. Sorbus experienced wide water potential variations and reached a minimum of -4.2 MPa during drought. Under the same microclimatic conditions, Sambucus experienced consistent stem water potentials with a minimum of -1.7 MPa. The relationship between percentage loss in hydraulic conductivity (PLC) and water potential (hydraulic vulnerability curve) of the two species differed in shape: a flat curve with nearly total loss of conductivity at -6 MPa was found for SORBUS: Sambucus showed a steep vulnerability curve with 90% loss conductivity at -2.2 MPa. Thus, Sambucus is extremely vulnerable to cavitation, but Sorbus is an almost invulnerable species. This different cavitation resistance adjusted the ranges of field stem water potential that the species experienced. Finally, seasonal courses of naturally occurring (native) embolism were compared with calculated PLC courses. This comparison indicates that Sorbus did not refill embolized xylem vessels whereas Sambucus reversed embolism. It was concluded that species which are highly vulnerable to cavitation and drought-induced embolism need refilling of embolized vessels as well as isohydric water potential patterns as two strategies of survival.

Biological Transport↗
PubMed2002

Carbon isotope discrimination and bundle sheath leakiness in three C(4) subtypes grown under variable nitrogen, water and atmospheric CO(2) supply.

The changes in composition and productivity of semi-arid C(4) grassland, anticipated with rising atmospheric CO(2), will depend on soil water and nutrient availability. The interactive effects of soil resource limitation and elevated CO(2 )on these grasses, furthermore, may vary among C(4) biochemical subtypes (NADP-ME, NAD-ME, PCK) that differ in bundle sheath leakiness (Phi) responses to drought and nitrogen supply. To address C(4) subtype responses to soil resource gradients, the carbon isotope discrimination (Delta), bundle sheath leakiness (Phi), leaf gas exchange (A, g(s), c(i)/c(a)) and above-ground biomass accumulation were measured on three dominant grasses of semi-desert grassland in south-eastern Arizona. Bouteloua curtipendula (PCK), Aristida glabrata (NADP-ME) and the non-native Eragrostis lehmanniana (NAD-ME) were grown in controlled-environment chambers from seed under a complete, multi-factorial combination of present ambient (370 ppm) and elevated (690 ppm) CO(2) concentration and under high and low water and nitrogen supply. E. lehmanniana (NAD-ME) had the highest photosynthetic rate (A) and lowest Phi compared to the other two grasses when grown under low nitrogen and water availability. However, favourable water and nitrogen supply and elevated atmospheric CO(2) enhanced photosynthetic performance and above-ground biomass production of B. curtipendula (PCK) to a greater extent than in A. glabrata and E. lehmanniana. Contrary to pre vious studies, Phi and Delta in the NADP-ME subtype (A. glabrata) were most affected by changing environmental conditions compared to the other subtypes; deviations from the classic NADP-ME anatomy in Aristida could have accounted for this result. Overall, response of semi-arid grasslands to rising atmospheric CO(2) may depend more on species-specific responses to drought and nitrogen limitation than on general C(4) subtype responses.

Algorithms↗