Amino Acid Transport in Spores of Aspergillusoryzae

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Abstract
In dormant conidia of Aspergillus oryzae, L-leucine is transported by two distinct systems: one is inhibited by L-arginine and the other is not. The former was much more sensitive to inhibition by lithiumdiiodosalicylate, osmotic shock, pronase digestion, and high temperature than the latter. The activities of bothsystems began to increase after the conidia were incubated in phosphate buffer, in which no germination occurred.The increase in the activity of the arginine-insensitive system started soon after the incubation of the conidia,whereas the increase in that of the arginine-sensitive system was delayed for about 2 hr. No increase in these activities was observed at 0°C or in the presence of cycloheximide. When the conidia were incubated in a germination medium, essentially the same changes were observed, but to a much greater extent. It is proposed that the dormancy is maintained by a ‘membrane brake’ mechanism, and is broken by a conformational change in the membrane caused by the intake of water. The initial events of spore germination may be divided into two steps. The first step, which includes the increase in amino acid transport activities, is triggered by the intake of water and levels off after several hours unless germinants are supplied. The second step is triggered by the germinants only after the first step has proceeded to a considerable degree.

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