Wall-Less Prokaryotes of Plants

Abstract

The first mention of an association between wall-less prokaryotes and plants was published by Doi et al (53) in Japanese in 1967 in a work entitled, "Mycoplasma or PLT:group-like microorganisms found in the phloem ele ments of plants infected with mulberry dwarf, potato witches' broom, aster yellows, or paulownia witches' broom."J Similar microorganisms had been seen at about the same time in rice infected with yellow dwarf disease (121). When plants containing the newly discovered microorganisms were given tetracycline treatments, symptom remission occurred as long as the antibiotic application lasted, and the observed microorganisms disappeared temporarily from the phloem of these plants (76,121). Penicillin treatments had no effect. These results have been amply confirmed (108, 153). Because mycoplasmas were known to be sensitive to tetracycline but not penicillin, whereas the PLT agents were affected by both of these antibiotics (7, 75; see also 50), the microorganisms found by the Japanese workers were considered mycoplasma like and not chlamydiae-like and have been called mycoplasma-like organisms (MLOs).2 Similar MLOs have since been found to be associated with more than 100 diseases in plants (103).Mycoplasmas and permanent (irreversible) L-variants (161) of bacteria have 'PLT refers to psittacosis-lymphogranuloma-trachoma; the agents of these diseases are the Chlamydiae, a group of obligate intracellular parasites with a Gram-negative type of cell envelope.2The trivial lenn mycoplasma in the phrase MLO is used as a synonym for mollicute and does not imply the genus Mycoplasma. The name mollicute was first proposed in 1967 (59).

Chromosomal Gene Transfer in Spiroplasma citri

“…SPIROPLASMA CITRI IS A HELICAL mollicute, pathogenic for citrus trees (1). Mollicutes are mainly characterized by absence of cell wall and by a small sized genome (2).…”

Antibodies in plant science

“…Of the phloem-restricted endocellular pathogens: spiroplasmas, mycoplasma (MLO) and bacteria-like organisms (BLO), only the spirolplasmas can be grown in culture. Bove (1984) and others using antisera specific for a number of spiroplasmas have been able to detect and differentiate the organisms into various serogroups. It is very difficult, however, to raise antisera specific to mycoplasma-like organisms, partially because they are obligate pathogens, but also because they are only present in small numbers in infected plants.…”

DNA probes in detection of spiroplasmas and mycoplasma-like organisms in plants and insects

“…Over 200 economically important plant diseases transmitted by insects, mostly leafhoppers, have been ascribed to MLOs. However, despite numerous attempts, none of the MLOs associated with plant diseases has been cultivated in vitro [1].…”