Brefeldin A affects growth, endoplasmic reticulum, golgi bodies, tubular vacuole system, and secretory pathway in Pisolithus tinctorius

Brefeldin A (BFA) reduced radial growth in Pisolithus tinctorius at a conce ntration as low as 2 mu M. Use of endoplasmic reticulum (ER)Tracker dye, un conjugated BFA, and fluorescent BFA (BODIPY-BFA) allowed comparison of the effects of BFA on the endomembrane system of P. tinctorius at the light and electron microscope levels. Both ER-Tracker dye and BODIPY-BFA have been s hown previously to label the ER, Unconjugated BFA and BODIPY-BFA modified t he ER network and disrupted the tubular vacuole system in the tip region. T he ultrastructure in freeze-substituted hyphae showed that BFA treatment re sulted in (i) disruption of the Spitzenkorper, (ii) reduction in number of apical vesicles, (iii) redistribution and mild dilation of ER, and (iv) per sistence and increased size and complexity of Golgi bodies. The effects of BFA on the ER were only partially reversible in the time period examined. W e conclude that in P, tinctorius, BFA as the free metabolite or BODIPY-BFA affects the tubular vacuole system as well as anterograde membrane flow bet ween the ER and the Golgi bodies and post-Golgi transport. (C) 2000 Academi c Press.