SUMMARY
Alternaria species are mainly saprophytic fungi However, some species have acquired pathogenic capacities collectively causing disease over a broad host range This review summarizes the knowledge on pathogenic strategies employed by the fungus to plunder the host Furthermore, strategies employed by potential host plants in order to ward off an attack are discussed

Taxonomy:Alternaria spp kingdom Fungi, subkingdom Eumycotera, phylum Fungi Imperfecti (a non-phylogenetic or artificial phylum of fungi without known sexual stages whose members may or may not be related; taxonomy does not reflect relationships), form class Hypomycetes, Form order Moniliales, form family Dematiaceae, genus Alternaria Some species of Alternaria are the asexual anamorph of the ascomycete Pleospora while others are speculated to be anamorphs of Leptosphaeria

Host Range: Most Alternaria species are common saprophytes that derive energy as a result of cellulytic activity and are found in a variety of habitats as ubiquitous agents of decay Some species are plant pathogens that cause a range of economically important diseases like stem cancer, leaf blight or leaf spot on a large variety of crops Latent infections can occur and result in post-harvest diseases or damping-off in case of infected seed

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Alternaria spp.: from general saprophyte to specific parasite.

The Bond-Valence Method: An Empirical Approach to Chemical Structure and Bonding

Host-selective toxins, a group of structurally complex and chemically diverse metabolites produced by plant pathogenic strains of certain fungal species, function as essential determinants of pathogenicity or virulence. Investigations into the molecular and biochemical responses to these disease determinants reveal responses typically associated with host defense and incompatibility induced by avirulence determinants. The characteristic responses that unify these disparate disease phenotypes are numerous, yet the evidence implicating a causal relationship of these responses, whether induced by host-selective toxins or avirulence factors, in determining the consequences of the host-pathogen interaction is equivocal. This review summarizes some examples of the action of host-selective toxins to illustrate the similarity in responses with those to avirulence determinants.

HOST-SELECTIVE TOXINS AND AVIRULENCE DETERMINANTS: What's in a Name?*

Microfungi of the genus Alternaria are ubiquitous pathogens and saprophytes. Many species of the genus Alternaria commonly cause spoilage of various food crops in the field or post-harvest decay. Due to their growth even at low temperatures, they are also responsible for spoilage of these commodities during refrigerated transport and storage. Several Alternaria species are known producers of toxic secondary metabolites - Alternaria mycotoxins. A. alternata produces a number of mycotoxins, including alternariol, alternariol monomethyl ether, altenuene, altertoxins I, II, III, tenuazonic acid and other less toxic metabolites. Tenuazonic acid is toxic to several animal species, e.g. mice, chicken, dogs. Alternariol, alternariol monomethyl ether, altenuene and altertoxin I are not very acutely toxic. There are several reports on the mutagenicity and genotoxicity of alternariol, and alternariol monomethyl ether. Alternariol has been identified as a topoisomerase I and II poison which might contribute to the impairment of DNA integrity in human colon carcinoma cells. Analytical methods to determine Alternaria toxins are largely based on procedures, involving cleanup by solvent partitioning or solid phase extraction, followed by chromatographic separation techniques, in combination with ultraviolet, fluorescence, electrochemical and mass spectroscopic detection. A large number of Alternaria metabolites has been reported to occur naturally in food commodities (e.g. fruit, vegetables, cereals and oil plants). Alternariol, alternariol monomethyl ether and tenuazonic acid were frequently detected in apples, apple products, mandarins, olives, pepper, red pepper, tomatoes, tomato products, oilseed rape meal, sunflower seeds, sorghum, wheat and edible oils. Alternariol and alternariol monomethyl ether were detected in citrus fruit, Japanese pears, prune nectar, raspberries, red currant, carrots, barley and oats. Alternariol monomethyl ether and tenuazonic acid were detected in melon. Natural occurrence of alternariol has been reported in apple juice, cranberry juice, grape juice, prune nectar, raspberry juice, red wine and lentils.

Alternaria mycotoxins: an overview of chemical characterization, producers, toxicity, analysis and occurrence in foodstuffs

We thank the Spanish Ministerio de Ciencia e Innovacion (Grant Nos. CTQ2007-65218 and Consolider Ingenio 2010-CSD-2007-00006 and CTQ2011-24165), the Generalitat Valenciana (Grant No. PROMETEO/2009/039 and FEDER), and the University of Alicante for generous and continuous financial support.

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Diastereoselective allylation of carbonyl compounds and imines: application to the synthesis of natural products.

Two host-specific phytotoxic metabolites, AK-toxin I and II, were isolated from a culture broth of Alternaria alternata Japanese pear pathotype, the fungus causing black spot disease of susceptible Japanese pear cultivars. From chemical, spectral and X-ray crystallographic data, AK-toxin I was characterized as 8-(2′S, 3′S)-2′-acetylamino-3′-methyl-3′-phenyl-propionyloxy]-(8R,9S)-9,10-epoxy-9-methyl-deca-(2E,4Z,6E)-trienoic acid. The structure of AK-toxin II was also assigned to be 3′-demethyl derivative of AK-toxin I by comparing the spectral data with those of AK-toxin I.

Isolation and Structures of AK-Toxin I and II, Host-specific Phytotoxic Metabolites Produced by Alternaria alternata Japanese Pear Pathotype

The crystal structure of aspirin has been redetermined by X-ray diffraction analysis at room temperature. The lattice energy, the eleastic constants and the structure parameters corresponding to the equilibrium of a model potential of aspirin crystal have been calculated by taking account of the non-rigidity of the molecule and applying the condition of vanishing stress. The model potential consists of the exp-6 type dispersion and exchange repulsion terms, the Lippincott type hydrogen bond stretching terms and the electrostatic interaction terms between fixed atomic charges. The atomic coordinates of the calculated structure agree well with those determined crystallographically.

Structure redetermination and packing analysis of aspirin crystal.

The structure (I) of a new alkaloid, stemofoline isolated from the stems and leaves of Stemona japonica has been determined by X-ray crystallographic analysis of its hydrobromide monohydrate.

The crystal structure of a new alkaloid, stemofoline, from Stemona japonica

Acutumine and acutumidine, chlorine containing alkaloids with a novel skeleton (1): X-ray analysis of acutumine.

Structures of acutumine (XXXVIIa) and acutumidine (XXXVIIb), isolated from Menispermum dauricum DC. and Sinomenium acutum REHD. et WILS. (Menispermaceae), were investigated. On the basis of a series of degradative and spectroscopic evidences, their structures including absolute stereochemistry are assigned to the formula XXXVIIa and XXXVIIb, respectively, which are in good agreement with the result obtained from the X-ray analyses of acutumine and acetylacutumine. Apparently, these alkaloids represent a new class of alkaloids with a novel skeleton and also provide rare examples of chlorine-containing alkaloids.

Studies on the Alkaloids of Menispermaceous Plants. CCLIX. Alkaloids of Menispermum dauricum DC. (Suppl. 7). Structures of Acutumine and Acutumidine, Chlorine-Containing Alkaloids with a Novel Skeleton

Kenji Osaki

Papers

Isolation and Structures of AK-Toxin I and II, Host-specific Phytotoxic Metabolites Produced by Alternaria alternata Japanese Pear Pathotype

Structure redetermination and packing analysis of aspirin crystal.

The crystal structure of a new alkaloid, stemofoline, from Stemona japonica

Acutumine and acutumidine, chlorine containing alkaloids with a novel skeleton (1): X-ray analysis of acutumine.

Studies on the Alkaloids of Menispermaceous Plants. CCLIX. Alkaloids of Menispermum dauricum DC. (Suppl. 7). Structures of Acutumine and Acutumidine, Chlorine-Containing Alkaloids with a Novel Skeleton