Distribution of cellular amino acids, protein, and total organic nitrogen during fruit body development in Flammulina velutipes. II. Growth on potato–glucose solution

Abstract

In Flammulina velutipes grown on potato–glucose solution the dry weight of mycelium decreased when fruitbodies elongated rapidly. Loss of dry weight by aborted primordia and stunted fruitbodies paralleled gains by large fruitbodies. These gains exceeded the losses by the rest of the colony and indicate that large fruitbodies derived their substrates both from the medium and from materials stored in the rest of the colony. Close to 43% of the organic nitrogen in the medium was consumed before fruitbodies formed and only 8% remained at the end of their growth. Concentrations of total nitrogen, α-amino nitrogen, and alkali-soluble protein declined in the mycelium during most of the growth of the fruitbodies and then remained constant except for a slight final increase in protein. Concentrations of these fractions also decreased in the small fruitbodies and stipes of large fruitbodies but increased in the pilei. Changes in total amounts of these fractions show that gains by all fruitbodies during elongation exceeded the losses by the mycelium and that part of their nitrogen continues to be derived from the medium. Changes in 18 free and 17 protein amino acids were followed quantitatively in the colony. Free arginine, glutamic acid, ornithine, and alanine predominated in the mycelium and small fruitbodies during early growth of the latter, but arginine and ornithine decreased steeply thereafter. During rapid elongation of the large fruitbodies the concentration of arginine increased strongly in the pilei. The increase was much less in the stipes, but successive changes in the rest of the colony suggest that arginine is translocated into the large pilei from the mycelium and possibly the small fruitbodies. Aspartic and glutamic acids, leucine, and alanine predominated in protein of the whole colony until the early growth of fruitbodies, but protein composition changed during rapid elongation. The proportion of valine increased in the mycelium and it became the most abundant bound amino acid in large stipes. [14C]Leucine was fed in replacement medium and incorporation of the label was determined in nitrogenous fractions of different colony portions at the onset and termination of fruitbody growth. Most of the label transported into fruitbodies was in the ethanol-soluble free amino acids.