MULTICELLULAR STALK-LIKE STRUCTURES IN SACCHAROMYCES-CEREVISIAE

Stalk formation is a novel pattern of multicellular organization. Yeas t cells which survive UV irradiation form colonies that grow verticall y to form very long (0.5 to 3.0 cm) and thin (0.5 to 4 mm in diameter) multicellular structures. We describe the conditions required to obta in these stalk-like structures reproducibly in large numbers. Yeast mu tants, mutated for control of cell polarity, developmental processes, UV response, and signal transduction cascades were tested and found ca pable of forming stalk-like structures. We suggest a model that explai ns the mechanism of stalk formation by mechanical environmental forces . We show that other microorganisms (Candida albicans, Schizosaccharom yces pombe, and Escherichia coli) also form stalks, suggesting that th e ability to produce stalks may be a general property of microorganism s, Diploid yeast stalks sporulate at an elevated frequency, raising th e possibility that the physiological role of stalks might be dissemina ting spores.