Fungal sex hormones

Fungal sex hormones

1. SEX HORMONES IN FUNGI KKR1116 1

2. SEX HORMONES IN FUNGI The presence of sex hormones in dioecious species of Achlya was first reported in 1881 by De Bary . In 1908, Kaufmann supported the contention of De Bary on the basis of his observations on Saprolegnia hypogyna . HORMONES are the chemical substance that are produced in one part of an organism and moves to another part by diffusion, where it can induce specific response. The hormones are produced by cells, that have profound morphogenetic effects on other cells of the same species or closely related species. KKR1116 2

3. They regulate the temporal and spatial coordination which leads to the sexual pairing and fusion of nuclei. The hormones are released from their site of synthesis and by diffusion they define the cells that will be involved in the sexual interactions. They are produced in very small quantities. KKR1116 3

4. Although known as sex hormones when discovered first, These organic substances are actually called as sex pheromones. They are the chemicals produced by one partner to elicit a sexual response in the other. DEFINITION AND TERMINOLOGY: Van Den Ende (1967), defined sexual hormone as a diffusible substance playing a specific role in the sexual reproduction of the organism that produces it. KKR1116 4

5. Machlis (1972) coined the following terms : EROTACTINS : Is a sexual hormone which attracts motile gametes EROTROPIN : It is a sex hormone that induces chemotrophic growth of sexual structures. EROGENS : Is the sex hormone that controls the induction and differentiation of sexual structures. However, the sex hormone may perform more than one function. As in Achlya , the hormone that controls development of sexual structures also determines the direction of the sex organs. KKR1116 5

6. Although a large number of sex hormones have been reported, only a few have been chemically characterized and extensively studied. Some important hormones are: SIRENIN ANTHERIDIOL OOGONIAL TRISPORIC ACID YEAST D FACTOR ( Sirenin - from Allomyces : It is a sperm attractant.) (Both Antheridiol and Oogonial i nduces differentiation of sex organs and also functions as chemotactic agents). KKR1116 6

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8. SIRENIN Sirenin was the first fungal sex hormone to have its structure determined. In Allomyces ( Blastocladiales , Chytridiomycetes ), sexual reproduction requires the fusion between uniflagellate motile male and female gametes where the male gametes are smaller than the female gametes. Machlis (1958, 1966) and his collaborators showed that the male gametes are attracted to female gametangia due to the production of an attractant. Sirenin is produced by both the female gametangia and the female gametes, which is released into the water. KKR1116 8

9. The male gametes, under the influence of this hormone, surrounds the female gametangia. Pairing of the male and female gametes results in the formation of diploid motile zygotes. The adhesive contact which leads to plasmogamy is blocked if BORIC ACID is added (specific surface polysaccharides may be involved). Sirenin is active at very low concentrations, which is less than 10 -10 g ml -1 , but it does not affect the diploid gametes. KKR1116 9

10. ISOLATION AND CHEMICAL CHARACTERIZATION: Isolation is from interspecific female hybrids of Alomyces macrogynous and Allomyces arbuscula. Structure: Oxygenated sesquiterpene maybe species specific Two forms: D and L (biologically effective). Empirical Formula: C 15  H  24 O 2 Molecular weight: 236 KKR1116 10

11. BIOASSAY OF SIRENIN: Test solution with cellophane base in test tube is taken and immersed in vessel containing water and male gametes. The clustering of male gametes around cellophane base indicates the presence of sirenin . KKR1116 11

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13. CHEMOTAXIS IN Allomyces : 5 types of motile cells are formed: Haploid zoospores Diploid zoospores Male gametes: Which shows r esponse to sirenin , im mmediately after fertilization they stop responding and the resulting zygote shows positive chemotactic response towards amino acids. Female gametes The zygotes 2 Zoospores and Zygotes shows no respose to the hormone but they are attracted towards amino acid. KKR1116 13

14. ANTHERIDIOL & OOGONIAL (HORMONE B) The definite proof that sexual hormones occur in Achlya was published by Raper in a series of papers that appeared between 1939-1952. (Sexual Hormones in Achlya VI. The Hormones of the A-Complex * John R. Raper ) Raper worked with unisexual (dioecious) species Achlya ambisexuals and Achlya bisexualis . He found that the vegetative female filament secreted hormone A which induced Antheridiol in male. KKR1116 14

15. Hormone A is a mixture of four hormones: two secreted by the female hyphae (A 2 & A) and the two produced by the male hyphae (A 1 & A 3 ). Later the male hyphae produced hormone B which induced the development of Oogonia in the female. The Oogonial hyphae releases hormone C. This hormone helps in the fusion of antheridia to the oogonia. KKR1116 15

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17. Antheridiol Antheridiol is an hormone which elicits following responses: Induction of antheridiol hyphae Chemotropic stimulation of male hyphae to produce hormone B Delimitation of antheridia KKR1116 17

18. CHEMICAL NATURE AND STRUCTURE: Isolated in crystalline form by McMorris and Barksdale (1967). Structure was proposed by Arsenault et la (1969). It is a steroid hormone which is active at concentration down to 10 -10 M.   BIOASSAY OF ATHERIDIOL: Test sample should induce formation of antheridial hyphae in pure male Achlya ambisexualis in absence of female isolate. KKR1116 18

19. B . Oogonial The hormone is synthesized by male hyphae of Achlya ambisexualis which happens only in the presence of antheridiol . Barksdale et al (1974) reported that some hermaphrodite strains produce oogonial without stimulus of antheridiol . KKR1116 19

20. Oogonial-1, R= [CH 3 ] 2 -CHO=O Oogonial-2, R= CH 3 CH 2 C=O McMorris and his co-workers (1975) isolated 2 crystalline compounds from Achlya heterosexualis , which possess hormone-B activity named as oogonial-1 and oogonial-2. Oogonial is a crystalline steroid with molecular weight 500. The hormone stimulates the development of oogonium on female hyphae. KKR1116 20

21. TRISPORIC ACID It has been found to play active role in sexual reproduction of several members of the order Mucorales such as; Mucor mucedo , Blakeslea trispora and Phycomyces blakesleeanus . Sexual interactions involve mutual stimulation for zygospore formation. DISCOVERY: Though the concept of sex hormone in Mucorales was developed in 1924 by Burgeff , it was only in 1956 that Burgeff could isolate a sex hormone in a cell free extract and this sex hormone was named as Trisporic Acid. KKR1116 21

22. For a long time, this acid was known as a metabolite associated with carotenogenesis . Trisporic acid is an unsaturated & oxygenated form of trimethyl cyclo-hexane. KKR1116 22

23. Empirical Formula: C 15  H  26 O 4 Molecular Formula: 306 So far three kinds of trisporic acid have been identified: Trisporic acid A: shows only 1% of activity, perhaps due to lack of functional group in side chain. 2 . Trisporic acid B: 15% activity. 3. Trisporic acid C: 80% activity (plays a major role). KKR1116 23

24. PRODUCTION OF TRISPORIC ACID BY Mucorales : In the heterothallic mycelia, trisporic acid B & C stimulate the development of zygophores . This hormone is synthesized only when the mycelia of (+) & (-) strains grow in a normal continuous diffusible medium. The hormone which is synthesized in the (-) strain induces the development of Progametangium in (-) strain and viceversa . The zygophores of (+) & (-) strain are attracted towards each other due to chemotropic response of a volatile substance which also promotes the synthesis of trisporic acid in 2 opposite mating types. KKR1116 24

25. ZYGOTROPISM: It is a process in which the zygophores of (+) and (-) strain are attracted towards each other due to chemotropic response of a volatile substance, suggested by Banbury (1954) and Plempel (1960-1963), which also promotes the synthesis of trisporic acid in two opposite mating types (Gooday, 1973). KKR1116 25

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27. YEAST α- FACTOR   The presence and the involvement of some hormone in the sexual reproduction of Saccharomyces cerevisiae was discovered by Levi in the year 1950. In this fungus, the haploid cells are of two mating types; a and α . Which conjugate to form diploid cells. When two such cells are in close proximity, budding is initiated and the cells elongate towards each other.   In 1956, Levi showed that the α- haploid cells produce a diffusible chemical which induces the formation of copulatory process by compatible a -cells, due to which it stops their growth and reproduction by budding. Instead, these a -cells swell in size and form gaint cells of various shapes. KKR1116 27

28. The α -factor acts only on a -cells and has no effect on α -cells. The α -factor is reported to inhibit DNA replication in the a -cells. CHEMICAL STRUCTURE: Duntze (1970-1973) isolated the α -factor in pure form. It is peptide complexed with copper ions and has molecular weight of 1400. BIOASSAY: The test should induce the formation of copulatory processes specifically in a -cells and transforms into giant cells. KKR1116 28

29. Two haploid yeast of opposite mating types secrete pheromones, grow projections and mate. KKR1116 29

30. REFERENCES Fungus - Sexual reproduction | Britannica biochemj00633-0138.pdf (nih.gov) 1461.full.pdf (plantcell.org) CHAPTER 21 (uncw.edu) Sexual Hormones in Achlya (nih.gov) Botany for Degree Students (FUNGI) by B R VASHISHTA & A K SINHA An introduction to MYCOLOGY by K R ANEJA & R S MEHROTRA Youtube and Google for images KKR1116 30

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