A role for the Swe1 checkpoint kinase during filamentous growth of Saccharomyces cerevisiae

In this study we show that inactivation of Hs11 or Hs17, negative regulator s of the Swel kinase, enhances the invasive behavior of haploid and diploid cells. The enhancement of filamentous growth caused by inactivation of bot h genes is mediated via the Swel protein kinase. Whereas Swel contributes n oticeably to the effectiveness of haploid invasive growth under all conditi ons tested, its contribution to pseudohyphal growth is limited to the morph ological response under standard assay conditions. However, Swel is essenti al for pseudohyphal differentiation under a number of nonstandard assay con ditions including altered temperature and increased nitrogen. Swel is also required for pseudohyphal growth in the absence of Tecl and for the inducti on of filamentation by butanol, a related phenomenon. Although inactivation of Hs11 is sufficient to suppress the defect in filamentous growth caused by inactivation of Tec1 or Flo8, it is insufficient to promote filamentous growth in the absence of both factors. Moreover, inactivation of Hs11 will not bypass the requirement for nitrogen starvation or growth on solid mediu m for pseudohyphal differentiation. We conclude that the Swel kinase modula tes filamentous development under a broad spectrum of conditions and that i ts role is partially redundant with the Tec1 and Flo8 transcription factors .