Differentiation-related proteins of the broad bean rust fungus Uromyces viciae-fabae,as revealed by high resolution two-dimensional polyacrylamide gel electrophoresis

On artificial polyethylene membranes providing a thigmotropic signal, uredospores of the broad bean rust fungus Uromyces viciae-fabae differentiated a series of infection structures which in nature are necessary to invade the host tissue through the stomata. Within 24 h germ tubes, appressoria, substomatal vesicles, infection hyphae and haustorial mother cells were developed successively. Alterations in protein metabolism during infection structure differentiation of this obligate plant pathogen were analyzed in the absence of the host plant by high resolution two-dimensional polyacrylamide gel electrophoresis (2-DE) and silver staining. The norm pattern representing the 2-DE protein patterns of the whole developmental sequence of infection structures of U. viciae-fabae showed 733 spots. During infection structure differentiation 55 proteins were newly formed, altered in quantity, or disappeared. Major alterations in the protein pattern occurred during uredospore germination and when infection hyphae were formed. Uredospore germination was characterized by a decrease of acidic proteins and an increase mainly of proteins with isoelectric points ranging from weakly acidic to basic.Abbreviations 2-DE two-dimensional polyacrylamide gel electrophoresis - DAPI 4,6-diamino-phenylindol - kDa kilo Dalton - pl isoelectric point - PMSF phenylmethylsulfonyl fluoride - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis     

The effect of a foliar disease (rust) on the development of Gastrophysa viridula (Coleoptera: Chrysomelidae)

Abstract.

• 1 Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae) and the pathogenic rust fungus Uromyces rumicis (Schum.) Wint. both occur on leaves of Rumex crispus L. and R.obtusifolius L. Individual stages of beetle development, and egg laying, were compared on healthy and infected leaves of each plant species in the laboratory. Oviposition choice was investigated in the field and laboratory.
• 2 Beetles reared on infected leaves of each species had greater larval mortality and slower development than those reared on healthy leaves. Although larvae feeding on infected leaves consumed up to 2.5 times more dry weight than those reared on healthy leaves, they had a lower relative growth rate and pupated at a lower weight. These changes were consistent with the reduced nutritive quality of rust-infected Rumex leaves.
• 3 Fecundity of beetles reared on infected leaves of both species was considerably reduced. Eggs laid by beetles feeding on infected R.crispus leaves also had a reduced viability.
• 4 The beetle developed consistently poorer on healthy R.crispus than on healthy R.obtusifolius throughout its life-cycle. Differences in larval performance were greater between host species than between infected and healthy leaves.
• 5 Oviposition was similar on infected and healthy R.crispus in both the laboratory and field. However, adults consumed less, and laid fewer eggs on infected than on healthy R.obtusifolius. The pattern of egg laying on different aged leaves was affected by rust infection: a greater proportion of eggs was laid on the older, infected leaves, than on the equivalent aged leaves on the healthy plants. Few larvae survived from eggs laid on rusted leaves in the field.

     

豇豆单孢锈菌中病毒样颗粒中双链RNA的存在

从北京西郊清华园附近田间豇豆上采集的豇豆单孢锈菌(Uormyces vignal Barcl)夏孢子。萌发后提取双链RNA,电泳分析可测出300—8000碱基对的三组双链RNA。从萌发的孢子中通过差迷离心提取病毒样颗粒,可获得二种类型的病毒样颗粒,一种直径为35—40nm的等轴颗粒。另一种为长短不等的棒状颗粒,用提纯物提取核酸电泳分析与直接从孢子中提取的双链RNA有相同的核酸带,从而证明这些双链RNA存在于病毒样颗粒中。     

Phylogenetic analyses of <Emphasis Type="Italic">Uromyces viciae-fabae</Emphasis> and its varieties on <Emphasis Type="Italic">Vicia</Emphasis>, <Emphasis Type="Italic">Lathyrus</Emphasis>, and <Emphasis Type="Italic">Pisum</Emphasis> in Japan

A pea rust fungus, Uromyces viciae-fabae, has been classified into two varieties, var. viciae-fabae and var. orobi, based on differences in urediniospore wall thickness and putative host specificity in Japan. In principal component analyses, morphological features of urediniospores and teliospores of 94 rust specimens from Vicia, Lathyrus, and Pisum did not show definite host-specific morphological groups. In molecular analyses, 23 Uromyces specimens from Vicia, Lathyrus, and Pisum formed a single genetic clade based on D1/D2 and ITS regions. Four isolates of U. viciae-fabae from V. cracca and V. unijuga could infect and sporulate on P. sativum. These results suggest that U. viciae-fabae populations on different host plants are not biologically differentiated into groups that can be recognized as varieties.Contribution no. 184, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan     

Evaluation of Food Additives and Low-toxicity Compounds for the Control of Bean Rust and Wheat Leaf Rust

The efficacy of low‐toxicity chemicals as possible alternatives to synthetic fungicides for the control of Uromyces appendiculatus and Puccinia triticina was evaluated. A preliminary selection of food additives was performed through in vitro and in vivo preliminary screenings. The ED₅₀ and minimum inhibition concentration (MIC) values showed that most of the food additives used in this study were more toxic to U. appendiculatus than to P. triticina. Acetic acid, potassium carbonate, sodium carbonate and sodium molybdate were the food additives that were more toxic to the urediniospores of P. triticina. Selected compounds and concentrations were tested on bean and wheat plants grown in pots under controlled conditions. Acetic acid, ammonium bicarbonate, potassium acetate, potassium benzoate, potassium bicarbonate, potassium carbonate, sodium acetate and sodium citrate at 0.03, 0.09, 0.03, 0.006, 0.012, 0.012, 0.03 and 0.03 m , respectively, significantly reduced the disease severity of U. appendiculatus without causing any injury to bean leaves. Ammonium bicarbonate, potassium bicarbonate, sodium bicarbonate and sodium citrate at 0.12, 0.03, 0.12 and 0.03 m , respectively, were the most effective in reducing the disease severity caused by P. triticina without causing any injury to wheat leaves.     

Tête à tête inside a plant cell: establishing compatibility between plants and biotrophic fungi and oomycetes

'Compatibility' describes the complementary relationship between a plant species and an adapted pathogen species that underlies susceptibility and which ultimately results in disease. Owing to elaborate surveillance systems and defence mechanisms on the plant side and a common lack of adaptation of many microbial pathogens, resistance is the rule and compatibility the exception for most plant-microbe combinations. While there has been major scientific interest in 'resistance' in the past decade, which has revealed many of its underlying molecular components, the analysis of 'compatibility', although intimately intertwined with 'resistance', has not been pursued with a similar intensity. Various recent studies, however, provide a first glimpse of the pivotal players and potential molecular mechanisms essential for compatibility in both the plant and parasite partners. In this review we highlight these findings with a particular emphasis on obligate biotrophic and hemibiotrophic fungal and oomycete pathogens and discuss novel strategies that might help to uncover further the molecular principles underlying compatibility to these highly specialized pathogens.     

Genetic Variation Among and Within Uromyces Species Infecting Legumes

Genetic variation of 30 different Uromyces isolates collected on faba bean, lentil, common vetch, pea, chickpea, alfalfa, cowpea and lupin was studied. Random Amplified Polymorphic DNA markers were used showing clear differences among Uromyces species. Uromyces viciae-fabae isolates clustered according to the host, with a clear cluster including all U. viciae-fabae ex Vicia faba isolates. The U. viciae-fabae ex Lens culinaris isolate was the nearest to the cluster of U. viciae faba ex V. faba isolates, followed by U. pisi from Canada and U. viciae-fabae ex V. sativa . No association was found among molecular diversity and virulence or geographic origin within U. vicia-fabae ex V. faba isolates. Among the three U. pisi isolates considered, a great variability was observed and no grouping could be established. The most different isolate from the rest of species considered was U. striatus , followed by U. vignae . The two U. ciceris-arietini isolates clustered together and so did the two U. lupinicolus isolates.     

Effects of Angular Leaf Spot and Rust on Leaf Gas Exchange and Yield of Common Bean (Phaseolus Vulgaris)

Isolated and interactive effects of angular leaf spot (caused by Phaeoisariopsis griseola) and rust (caused by Uromyces appendiculatus) on leaf gas exchange and yield was studied in common bean (Phaseolus vulgaris L. cv. Carioca) plants. Gas exchange was measured on 37, 44, 51, and 58 d after planting using a portable photosynthesis system. The inoculation of plants with P. griseola (P), U. appendiculatus (U), and the combination of both pathogens (P+U) caused a significant reduction of net photosynthetic rate (P _N) and yield. The reduction of stomatal conductance (g _s), P _N, and yield was higher under P and combination of P+U than under U treatment. By effect of U, the reduction on yield was higher than the reductions on gas exchange parameters. On the treatment P+U, a reduction of 23 % in P _N and a correspondent reduction of 32 % in yield was observed. The interactive effects of the pathogens on yield could be explained in part by the decreases in g _s and in P _N of diseased bean leaves. The combined effect of both diseases on yield and gas exchange parameters suggests an antagonistic interaction.     

Gas Exchange and Emission of Chlorophyll Fluorescence during the Monocycle of Rust, Angular Leaf Spot and Anthracnose on Bean Leaves as a Function of their Trophic Characteristics

Measurements related to gas exchange and chlorophyll fluorescence emission were taken from healthy and diseased bean leaves with rust, angular leaf spot, and anthracnose during lesion development for each disease. The experiments were performed at different temperatures of plant incubation, and using two bean cultivars. The main effect of temperature of plant incubation was in disease development. There was no significant difference between cultivars in relation to disease development and in magnitude of physiological alterations when disease severity was the same for each cultivar. These diseases reduced the net photosynthetic rate and increased the dark respiration of infected leaves after the appearance of visible symptoms and the differences between healthy and diseased leaves increased with disease development. The transpiration rate and stomatal conductance were stable during the monocycle of rust, however, these two variables decreased in leaves with angular leaf spot and anthracnose beginning with symptom appearance and continuing until lesion development was complete. Carboxylation resistance was probably the main factor related to reduction of photosynthetic rate of the apparently healthy area of leaves with rust and angular leaf spot. Reduction of the intercellular concentration of CO₂, due to higher stomatal resistance, was probably the main factor for leaves with anthracnose. Chlorophyll fluorescence assessments suggested that there was no change in electron transport capacity and generation of ATP and NADPH in apparently healthy areas of diseased leaves, but decreases in chlorophyll fluorescence emission occurred on visibly lesioned areas for all diseases. Minimal fluorescence was remarkably reduced in leaves with angular leaf spot. Maximal fluorescence and optimal quantum yield of photosystem II of leaves were reduced for all three diseases. Bean rust, caused by a biotrophic pathogen, induced less damage to the regulation mechanisms of the physiological processes of the remaining green area of diseased leaves than did bean angular leaf spot or anthracnose, caused by hemibiotrophic pathogens. The magnitude of photosynthesis reduction can be related to the host–pathogen trophic relationships.