Phenylpropanoid compounds encompass a wide range of structural classes and biological functions. Limiting discussion to stress-induced phenylpropanoids eliminates few of the structural classes, because many compounds thst are constitutive in one plant species or tissue can be induced by various stresses in another species or in another tissue of the same plant (Beggs et al., 1987; Christie et al., 1994).

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Stress-Induced Phenylpropanoid Metabolism.

The role of flavonoids as the major red, blue, and purple pigments in plants has gained these secondary products a great deal of attention over the years. From the first description of acid and base effects on plant pigments by Robert Boyle in 1664 to the characterization of structural and

Flavonoid Biosynthesis. A Colorful Model for Genetics, Biochemistry, Cell Biology, and Biotechnology

The aim of this review was to survey all fungal pathologists with an association with the journal Molecular Plant Pathology and ask them to nominate which fungal pathogens they would place in a 'Top 10' based on scientific/economic importance. The survey generated 495 votes from the international community, and resulted in the generation of a Top 10 fungal plant pathogen list for Molecular Plant Pathology. The Top 10 list includes, in rank order, (1) Magnaporthe oryzae; (2) Botrytis cinerea; (3) Puccinia spp.; (4) Fusarium graminearum; (5) Fusarium oxysporum; (6) Blumeria graminis; (7) Mycosphaerella graminicola; (8) Colletotrichum spp.; (9) Ustilago maydis; (10) Melampsora lini, with honourable mentions for fungi just missing out on the Top 10, including Phakopsora pachyrhizi and Rhizoctonia solani. This article presents a short resume of each fungus in the Top 10 list and its importance, with the intent of initiating discussion and debate amongst the plant mycology community, as well as laying down a bench-mark. It will be interesting to see in future years how perceptions change and what fungi will comprise any future Top 10.

/pdf/the-top-10-fungal-pathogens-in-molecular-plant-pathology-4nidxj1xqt.pdf

The Top 10 fungal pathogens in molecular plant pathology

Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds.

Fungal laccases - occurrence and properties.

Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Sorghum produces phytoalexins that are 3-deoxyanthocyanidin flavonoids. The compounds inhibit the growth of phytopathogenic fungi in vitro. The phytoalexins appear to be synthesized in subcellular inclusions within a host epidermal cell that is about to be penetrated by a fungus. This site-restricted synthesis suggests that the phytoalexin response occurs initially in the first cells that come under fungal attack and is not simply a response of cells that surround the original infection site.

https://science.sciencemag.org/content/sci/248/4963/1637.full.pdf

Synthesis of Phytoalexins in Sorghum as a Site-Specific Response to Fungal Ingress

Phenylalanine ammonia-lyase (E.C. 4.3.1.5) (PAL) and hydroxycinnamate:CoA ligase (E.C. 6.2.1.12) activities were measured in extracts from maize mesocotyls resistant and susceptible to Helminthosporium maydis and resistant to H. carbonum . CoA ligase activity increased in response to infection with H. maydis in both the resistant and susceptible cultivars. Activity began to increase between 6 and 9 h after inoculation and in the resistant cultivar continued to increase throughout a 48-h period. In susceptible cultivars activity ceased to increase at approximately 12 h after inoculation. The results demonstrate that the increase in CoA ligase activity is detectable as early as the onset of penetration by the fungus. No significant change in PAL activity was observed in either resistant or susceptible combinations with H. maydis , suggesting that PAL and CoA ligase are not coordinately regulated in interactions involving this fungus. Neither enzyme was found to change as a result of inoculation of any cultivar with H. carbonum .

Phenylalanine ammonia-lyase and hydroxycinnamate: CoA ligase in maize mesocotyls inoculated with Helminthosporium maydis or Helminthosporium carbonum

The Biology of Corn Anthracnose: Knowledge to Exploit for Improved Management.

Accumulation of 3-deoxyanthocyanidin phytoalexins and resistance to Colletotrichum sublineolum in sorghum

Sorghum (Sorghum bicolor L. Moench) accumulates the anthocyanin cyanidin 3-dimalonyl glucoside in etiolated mesocotyls in response to light. Inoculation with the nonpathogenic fungus Cochliobolus heterostrophus drastically reduced the light-induced accumulation of anthocyanin by repressing the transcription of the anthocyanin biosynthesis genes encoding flavanone 3-hydroxylase, dihydroflavonol 4-reductase, and anthocyanidin synthase. In contrast to these repression effects, fungal inoculation resulted in the synthesis of the four known 3-deoxyanthocyanidin phytoalexins and a corresponding activation of genes encoding the key branch-point enzymes in the phenylpropanoid pathway, phenylalanine ammonia-lyase and chalcone synthase. In addition, a gene encoding the pathogenesis-related protein PR-10 was strongly induced in response to inoculation. The accumulation of phytoalexins leveled off by 48 h after inoculation and was accompanied by a more rapid increase in the rate of anthocyanin accumulation. The results suggest that the plant represses less essential metabolic activities such as anthocyanin synthesis as a means of compensating for the immediate biochemical and physiological needs for the defense response.

Ralph L. Nicholson

Papers

Synthesis of Phytoalexins in Sorghum as a Site-Specific Response to Fungal Ingress

Phenylalanine ammonia-lyase and hydroxycinnamate: CoA ligase in maize mesocotyls inoculated with Helminthosporium maydis or Helminthosporium carbonum

The Biology of Corn Anthracnose: Knowledge to Exploit for Improved Management.

Accumulation of 3-deoxyanthocyanidin phytoalexins and resistance to Colletotrichum sublineolum in sorghum

Reduction of light-induced anthocyanin accumulation in inoculated sorghum mesocotyls : Implications for a compensatory role in the defense response