2. Phylum Dictyosteliomycota.pdf

2: Kingdom Protista - Phylum Dictyosteliomycota I. PHYLA OF SLIME MOLDS 1. Plasmodiophoromycota - endoparasitic slime molds 2. Dictyosteliomycota - cellular slime molds 3. Acrasiomycota - cellular slime molds 4. Myxomycota - plasmodial slime molds In some...

2: Kingdom Protista - Phylum Dictyosteliomycota I. PHYLA OF SLIME MOLDS 1. Plasmodiophoromycota - endoparasitic slime molds 2. Dictyosteliomycota - cellular slime molds 3. Acrasiomycota - cellular slime molds 4. Myxomycota - plasmodial slime molds In some literature, Dictyosteliomycota and Myxomycota = Amoebozoa, Plasmodiophoromycota = Cercozoa, and Acrasiomycota = Percolozoa. II. CELLULAR SLIME MOLDS  An organism that produces a trophic stage that lacks a cell wall  Phagotrophic – ability to engulf large food particulate inside cells  Trophic stages: [both lack CW, engulf food, and can multiply]  amoebae - uninucleate; aggregates  plasmodia - multinucleate A. Dictyosteliomycota (dictyostelids)  Pseudoplasmodium (non-feeding stage), also called grex or slug, is 1. Characteristics formed of 10- to 50,000 individual  Habitat: soil amoebae encased in cellulose sheath  about 3 genera, 150 species  Slug migrate in response to  First discovered in 1869 by Oskar Brefeld temperature, light, relative humidity  Dictyostelium discoideum isolated by Kenneth Raper (1935)  model organism for study of: cytokinesis, signaling, chemotaxis, phagocytosis, motility, cell sorting, cell type determination 2. Representative Genera a. Dictyostelium (discoideum)  unbranched or laterally branched fruiting bodies  free-living  forms uninucleate haploid myxamoebae with filose (filamentous) pseudopodia emerging from spores  Myxamoebae aggregate in response to chemical signal (acrasin; cAMP)  Aggregating amoebae adhere end-to- end PPTH 104. General Mycology 1st Semester 2425 | ipluna b. Polysphondilium - fruiting bodies consist of b. Sexual stage repetitive whorls of regularly spaced side  Heterothallic mating: fusion of cells branches that are of opposite mating types c. Acytostelium - forms acellular fruiting body resulting to the formation of a stalks macrocyst.  Macrocyst: multi-walled; 3. Life Cycle development begins with the a. Vegetative stage formation of a zygote which ingest  Myxamoeba stage the surrounding myxamoebae as it  free-living amoebae increases in size  unicellular form c. Asexual / social cycle  vegetative growth by mitotic division  Aggregation, mound, slug and culmination PPTH 104. General Mycology 1st Semester 2425 | ipluna  Note: Species in the cellular slime mold group are microscopic during most stages of their life cycle, when they exist as haploid (having one copy of each chromosome in the nucleus ), single-celled amoebae. 4. Structures Formed throughout their Life Cycle a. Aggregation - group formation through f. Culmination - stalk cells form a cellulose production of periodic cAMP pulses, which are framework on which the spore mass is lifted in detected, amplified and relayed by the the air surrounding myxamoebae. g. Sorocarp - a mature fruiting body; contains a b. Stream formation - attraction of cellular stalk and a mass of spores at the tip. myxamoebae to form a group h. Sorophore - stalk of the fruiting body which c. Mound - non-differentiated slug is made up of distinct cells d. Slug/Pseudoplasmodium - structure formed i. Sorus - apex of the stalk; has no peridium or after aggregation; typically consists of about wall enclosing the spores; enveloped in a drop 100, 000 cells; component amoebae retains of mucus individuality; role in migration e. Mexican hat - forms after the slug settles to one spot; posterior end spreads out and anterior end raised in the air PPTH 104. General Mycology 1st Semester 2425 | ipluna  B. Acrasiomycota (acrasids) 1. Characteristics  Habitat: dead plant parts, tree bark, dung  Aggregation of myxamoebae does not and soil involve cAMP  3 families, 5 genera, 15 species  No migration of pseudoplasmodium  Primarily associated with plant materials  All cells of sorocarp able to germinate  Lobose pseudopodia on myxamoebae  No known sexual reproduction  Biflagellate cells in some taxa 2. Life Cycle III. OTHER PHYLA A. Plasmodiophoromycota 1. Characteristics  46 species in 16 genera  endoparasitic slime molds  Trophic stage formed inside host cells  Obligate endoparasites of aquatic and terrestrial plants, algae and fungi  Cause abnormal enlargement of host cells (hypertrophy) /  abnormal multiplication of cells (hyperplasia)  may also cause stunting PPTH 104. General Mycology 1st Semester 2425 | ipluna  2. Life Cycle  Plasmodium develops in host cell with cruciform nuclear divisions  Cruciform nuclear divisions - unique type of nuclear division to produce a multinucleate protoplast or plasmodium  Intracellular plasmodium develops into either multilobed sporangium (mitotic process) or cystosorus (meiosis)  Zoospores or cysts released from host cell 3. Disease Cycle PPTH 104. General Mycology 1st Semester 2425 | ipluna  4. Representative Genera a. Plasmodiophora brassicae  described by M. Woronin (1877)  causes club root of crucifers  up to 10% of crucifer acreage worldwide is infested b. Spongosphora subterranea  causes potato powdery scab  potatoes become unmarketable due to the scabbed appearance  water-soaked lesions appear on foliage c. Polymyxa betae  Obligate parasite of root tissue  Host: Chenopodiaceae (including sugar beet)  Does not normally cause symptoms or disease of crops  Stunting or yellowing of leaves occur where the plants are particularly challenged (e.g. flooded)  Economic importance is as vector of rhizomania disease in sugar beets  Beet Necrotic Yellow Vein Virus (BNYVV) - transmitted in a persistent manner by P. betae. - not adsorbed to the exterior of the fungus but internalized - Experiments: 1. Infectivity of viriliferous zoospores and cystosori remained after treatment with antiserum, mild acid, or base which would be expected to inactivate externally bound virus. 2. The virus can be acquired and transmitted by several stages of the plasmophorid cycle: zoospore transmission, cystosori transmission PPTH 104. General Mycology 1st Semester 2425 | ipluna