Asparagine and regulation of photoinduced rhythm in Penicillium claviforme

A photosensitive reaction involved in the expression and regulation of the endogenous sporulation rhythm in Penicillium claviforme Bainier CBS 126-23 has been described earlier by our team. The present work shows that asparagine plays a central role in this periodic system. The 24–26 h periodicity, which becomes desynchronized over a few days, was affected by supplying asparagine (1 to 25 m M ). a) The rhythm remained synchronized for at least 3 weeks, for all the asparagine concentrations used, b) The period increased successively from one cycle to the next (from 35±3 h to 73±8 h over 6 cycles) for 1 m M asparagine. This period lengthening became less and less accentuated as the asparagine concentration was increased. At ≥10 m M , the period was stable; it was 33±5 h for 10 m M and 22±1.5 h for 25 m M asparagine. Otherwise asparagine could not elicit rhythmicity in darkness or in dim continuous light (≤5 μW m⁻²).