MEIOSIS IN THE OOMYCETES: I. A MICROSPECTROPHOTOMETRIC ANALYSIS OF NUCLEAR DEOXYRIBONUCLEIC ACID IN SAPROLEGNIA TERRESTRIS

摘要: A cytological and cytochemical examination of Saprolegnia terrestris Cookson was undertaken to resolve the conflict opinion regarding life cycle fungi in Saprolegniaceae, i.e., whether meiosis is zygotic or gametic. Microspectrophotometric analysis reveals that pre-divisional oogonial antheridial nuclei are 4C; a subsequent reduction division sex organs produces 1C male female gametes. These products coexist developing oospore presumably fuse produce diploid zygote. Analysis somatic hyphal shows 2C DNA content, with characteristic skew bimodal character indicative predominantly G1, some S-period G2 types. The evidence completely consistent gametic meiosis, predominant vegetative phase short haploid phase, refutes notion meiosis. Further ramifications work discussed along preliminary results related progress. THERE an increasing body indicating occurs during gametogenesis members Saprolegniales Peronosporales (Trow, 1895, 1899, 1904; Stevens, 1899; Sansome, 1961, 1963, 1965; Sansome Harris, 1962; Barksdale, 1966, 1968). Collectively this favor such interpretation. However, no report has been presented which is, itself, entirely convincing. occurrence first reported by Trow (1895, 1904) Stevens (1899). Two years later (1901) stated chromosome number improbable those he had studied. In next 50 numerous reports were made one mitotic rather than two divisions Oomycetes (see Schrader (1938) Ziegler (1953) claimed occurred germinating Saprolegniaceae. spite generally accepted view group fungi, question again raised through efforts (1961, 1965) Harris (1962). observations these investigators on gametangial several species may be summarized as follows: (1) successive occur associated nuclear size. (2) IReceived for publication 17 February 1969. Research supported Office General Research, University Georgia, Athens 30601. 2Present address: Division Sciences, Kirklani College, Clinton, N.Y. 13323. gametangia following second approximately four times undergoing division. (3) Chromosomal configurations loops present early anaphase figures. (4) Irregularities chromosomal behavior separation failure pairing. (5) Typical metaphase figures only gametangia. (6) Multiple associations more chromosomes (e.g., trivalents quadrivalents) occur. (7) bridge fragment occasionally nuclei. Clearly substantial. Nonetheless small, result photomicrographs support not Supporting her own contentions, (1963, aptly points out Ziegler's illustrations oogonia Achlya recurva show considerably larger supposed meiotic drawn at same magnification. doubt cast upon since zygote nucleus sectioned material clearly illustrated (p. 62Fig. 8, Fig. 24; p. 64: 34) being situated within ooplast (Moore Howard, 1968), vacuolar-like region oospore, organelle-containing cytoplasm. Mullins Raper (1965) genetic suggests ambisexualis Dictyuchus monosporus. pointed (1965), their also followed survival single product.