Mating and pathogenic development of the Smut fungus Ustilago maydis are regulated by one mitogen-activated protein kinase cascade.

In the phytopathogenic fungus Ustilago maydis, pheromone-mediated cell fusion is a prerequisite for the generation of the infectious dikaryon. The pheromone signal elevates transcription of the pheromone genes and elicits formation of conjugation hyphae. Cyclic AMP and mitogen-activated protein kinase (MAPK) signaling are involved in this process. The MAPK cascade is presumed to be composed of Ubc4 (MAPK kinase kinase), Fuz7 (MAPK kinase), and Ubc3/Kpp2 (MAPK). We isolated the kpp4 gene and found it to be allelic to ubc4. Epistasis analyses with constitutively active alleles of kpp4 and fuz7 substantiate that Kpp4, Fuz7, and Kpp2/Ubc3 are components of the same module. Moreover, we demonstrate that Fuz7 activates Kpp2 and shows interactions in vitro. Signaling via this cascade regulates expression of pheromone-responsive genes, presumably through acting on the transcription factor Prf1. Interestingly, the same cascade is needed for conjugation tube formation, and this process does not involve Prf1. In addition, fuz7 as well as kpp4 deletion strains are nonpathogenic, while kpp2 deletion mutants are only attenuated in pathogenesis. Here we show that strains expressing the unphosphorylatable allele kpp2(T182A/Y184F) are severely affected in tumor induction and display defects in early infection-related differentiation.

Patenting of genome research results.

In light of the enormous investments for the sequencing of genomes and the subsequent development of pharmaceuticals, obtaining patents for these results is a major goal of companies working in this area. This article focuses on the present situation concerning the possibility to obtain patent protection for genome research results, in particular at the European Patent Office (EPO), in the US and in Japan. Trilateral projects have recently been established to consolidate the cooperation for the administration of the practice to search, examine and grant patent applications in order to gain possible mutual benefits. Accordingly, this article aims to assist people working in the field of genomic research to understand the basic principles of obtaining patents for DNA inventions in light of the practice of the EPO, the United States Patent and Trademark Office (USPTO) and the Japanese Patent and Trademark Office (JPTO).

The histone deacetylase Hda1 from Ustilago maydis is essential for teliospore development.

In the corn smut fungus Ustilago maydis, pathogenic development is controlled by the b mating type locus that encodes the two homeodomain proteins bE and bW. A heterodimer of bE and bW controls a large set of genes, either directly by binding to cis regulatory sequences or indirectly via a b-dependent regulatory cascade. It is thought that several of the b-regulated genes contribute to processes involved in pathogenicity. In a screen for components of the b-dependent regulatory cascade we have isolated Hda1, a protein with homology to histone deacetylases of the RPD3 class. Hda1 can substitute for the histone deacetylase RPD3 in Saccharomyces cerevisiae, showing that it functions as a histone deacetylase. Deletion of hda1 results in the expression of several genes that are normally expressed only in the dikaryon, among these are several genes that are now expressed independently from their activation by the bE/bW heterodimer. hda1 mutant strains are capable to infect corn, and the proliferation of dikaryotic hyphae within the plant appears comparable to wild-type strains during initial developmental stages. Upon karyogamy, however, the proliferation to mature teliospores is blocked. The block in sporogenesis in Deltahda1 strains is probably a result of the deregulation of a specific set of genes whose temporal or spatial expression prevent the proper developmental progress.

Regulation of cell separation in the dimorphic fungus Ustilago maydis.

During its haploid phase the dimorphic fungus Ustilago maydis grows vegetatively by budding. We have identified two genes, don1 and don3, which control the separation of mother and daughter cells. Mutant cells form tree-like clusters in liquid culture and grow as ring-like (donut-shaped) colonies on solid medium. In wild-type U. maydis cells, two distinct septa are formed during cytokinesis and delimit a fragmentation zone. Cells defective for either don1 or don3 display only a single septum and fail to complete cell separation. don1 encodes a guanine nucleotide exchange factor (GEF) of the Dbl family specific for Rho/Rac GTPases. Don3 belongs to the germinal-centre-kinase (GC) subfamily of Ste20-like protein kinases. We have isolated the U. maydis homologues of the small GTP binding proteins Rho2, Rho3, Rac1 and Cdc42. Out of these, only Cdc42 interacts specifically with Don1 and Don3 in the yeast two-hybrid system. We propose that Don1 and Don3 regulate the initiation of the secondary septum, which is required for proper cell separation.