In 1949 I graduated with a B.Sc Hons. in Biology from the U of Manitoba and moved to Edmonton where I began research in plant pathology with the Canadian Dept of Agriculture mainly with the plant pathogen Helminthosporium sativum which causes root rot of cereal crops. One of the observations I noted was the wide range of susceptibility of wheat to this root rot fungus. The obvious question was whether this range was due to the plant's resistance or to the virulence status of the fungus. I zeroed in on the latter designing an experiment to determine whether I could alter the virulence of this pathogen.
I selected the addition of specific amino acids to the culture medium on which the fungus was cultivated in the laboratory, reasoning that the free amino acids present in the rhizosphere, i.e. the area immediately around the roots of cereals in their soil environment, might alter the kinds of proteins and amino acids to which the pathogen was exposed and that some of these proteins might in turn alter the virulence of this pathogen. For details of the experimental design, the blogger should refer to my master's thesis in the Department of Biochemistry ,University of Alberta entitled "Studies of the free and bound amino acids in healthy and diseased wheat roots" and to my publication. (Hrushovetz,S.B. Effects of amino acids on the virulence of Helminthosporium sativum to wheat seedlings. Phytopathology. 47261-264.1957).
What is epigenesis ? Epigenesis has been broadly defined as altering gene expression without altering the underlying DNA sequences, i.e. the genetic code as first described by Watson and Crick. According to Wikipedia, examples would include DNA methylation and Histone modification. To my knowledge there are no published reports of the possible epigenetic effects of amino acids on virulence. Although my experiments suggested epigenesis, it would have been worth while to see if this loss of virulence could be restored by sub cultivation of the fungus in the absence of these amino acid supplements This could have been done since for my doctorate thesis which I obtained from the U of Toronto 3 years later I demonstrated that this fungus has a "perfect or sexual stage"with ascus formation . See my 2 publications
However it is also possible that this loss of virulence may not be epigenesis. According to genetic molecular biologists the amino acids which are synthesized and linked by peptide bonds to form specific proteins are dependent on the sequences of the purine and pyrimidine bases in the genetic or triplet code My reasoning that the sequence of the amino acids in the polypeptide chain to form this final protein could be determined and/or influenced by the presence and/or absence of certain amino acids and/or by their concentration during the process of protein synthesis and/or cell division. If certain amino acids were selectively selected and incorporated into the polypeptide chain depending on their concentrations the resulting modified synthesized protein would behave differently for that period until the cell undergoes a mitotic division and presumably the genetic code would revert back to normal. It is also possible that this hypothesis for modifying protein structure may actually be the mechanism of epigenesis. Further the phenomenon of epigenesis would continue as long as the altered amino acid concentration were present. Once the normal amino acids returned for the genetic code then the cell at its next division would enable the genes to exert their normal function. Sounds complicated ? I hope not. Furthermore, if this reversal to the normal occurred at the next cell division than there is no way of detecting it.To prove that such a mechanism was at play I am sure my colleagues in molecular biology could devise experiments using tritium- labelled amino acids. I should also mention that because the dominant generation is the gametophyte, were all the nuclei are haploid and not the sporophytic generation were the cells are diploid like in humans, that gene dominance is not a factor.
However to me the fundamental question still remains unanswered : How can human cells or other organisms including microorganisms like fungi select from the nutritional bowl those amino acids if those amino acids are either not present in the immediate cell environment and/or are obligatory ? Obligatory nutrients are those which must be present in the environment-I dont know the nutrient requirements for growth in the case of fungi but for humans 8 of the 20 known amino acids are obligatory, i.e. must be present in our diet.
Whether you consider my research findings and/or my theories as epigenesis, Lysenkoism, Lamarckism, or gene mutation are probably still an open question. Indeed we may need to modify not only what we classify as epigenesis, but also our basic knowledge of how the genetic code functions to produce proteins and other macromolecules- Maybe Linus Pauling who received in 1954 the Nobel prize in biochemistry was on the right tract searching for a "triplet code " and that the generally accepted double helix model of Watson and Crick requires modification. Maybe Genetics 101 also require alterations?
As a footnote: In 1956 I resigned my position as an associate Plant Pathologist with the Canadian Department of agriculture to enter medicine so I never did this complementary research to support and/or reject my thesis, namely that removing these excess amino acids from the "nutrition bowl" to see if this would restore the normal virulence function of this pathogen, probably more importantly it might even explain the mechanism of virulence. I recall a recent webinar I reviewed, entitled " you are as healthy as your gut "
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