SciPy is an open-source scientific computing library for the Python programming language. Since its initial release in 2001, SciPy has become a de facto standard for leveraging scientific algorithms in Python, with over 600 unique code contributors, thousands of dependent packages, over 100,000 dependent repositories and millions of downloads per year. In this work, we provide an overview of the capabilities and development practices of SciPy 1.0 and highlight some recent technical developments.

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Haploid yeast cells of the a mating type secrete a peptide pheromone, a factor, which acts on cells of the a mating type to prepare them for conjugation. We show that the STE3 gene, which is required for mating only by a cells and is transcribed only in. a cells, likely encodes a cell-surface receptor for a factor. This view is based on three findings. First 1418The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

STE3 mRNA is present only in Saccharomyces cerevisiae a cells, not in a or ala cells, and the transcript level increases about fivefold when cells are treated with a-factor mating pheromone. Deletions in the 5' noncoding region of STE3 defined a 43-base-pair (bp) upstream activation sequence (UAS) that can impart both modes of regulation to a CYCI-lacZ fusion when substituted for the native CYCI UAS. UAS activity required the al product of MATa, which is known to be required for transcription of a-specific genes. A chromosomal deletion that removed only 14 bp of the STE3 UAS reduced STE3 transcript levels 50-to 100-fold, indicating that the UAS is essential for expression. The STE3 UAS shares a 26-bp homology with the 5' noncoding sequences of the only other known a-specific genes, MFal and MFa2. We view the homology as having two componentsa nearly palindromic 16-bp "P box" and an adjacent 10-bp "Q box." A synthetic STE3 P box was inactive as a UAS; a perfect palindrome P box was active in all three cell types. We propose that the P box is the binding site for a transcription activator, but that al acting via the Q box is required for this activator to bind to the imperfect P boxes of a-specific genes. Versions of the P box are also found upstream of a-specific genes, within the binding sites of the repressor a2 encoded by MATa. Thus, the products of MATa may render gene expression a or a-specific by controlling access of the same transcription activator to its binding site, the P box.Cell specialization is vital to the sexual life cycle of the yeast Saccharomyces cerevisiae. In S. cerevisiae, three types of cells occur. The two haploid cell types, a and a, are specialized for mating, whereas the a/a diploid cell type formed by mating of a and a cells is specialized for meiosis and sporulation. Each of the two haploid cell types expresses a specific set of genes that allows it to mate with cells of the opposite type. Among the cell-type-specific gene products are the small peptide pheromones, a factor and a factor, and the receptors for these pheromones. For example, only a cells secrete a factor and produce the cell surface receptor for a factor. These mating pheromones and receptors are the major components of a system that enables efficient mating of haploid cells of opposite type (for reviews, see references 20,21,41,47).How is this cell specialization controlled? The ultimate determinant of the cell type (mating type) of yeast cells is the MAT locus. Haploid a cells contain the MATa allele, which encodes two regulators, al and a2 (45). al is an activator of a-specific genes, which include the a-factor structural genes, MFaJ (26,39) and MFa2 (39), and the gene that encodes the a-factor receptor, STE3 (3,16,27,34). Conversely, the a2 product represses a-specific genes, which include the afactor structural genes, MFal and MFa2 (7), the a-factor receptor gene, STE2 (19,23,27,34), and two genes whose products are involved in pheromone metabolism, STE6 (9, 50) and BAR] (42). For both a-and a-specific genes, regu...