During plant infection, fungal pathogens employ an array of cell wall-degrading enzymes (CWDEs) that promote penetration of the host, as well as transcription factors that respond to external stimuli regulating the corresponding structural genes. The role of CWDEs in pathogenicity has been intensely studied, but remains controversial. This is largely due to the fact that targeted knockout of single CWDE genes tends to have little effect on virulence, due to the presence of multiple genes encoding similar enzymatic activities (functional redundancy), this fact indicates the convenience of simultaneous inactivation of related genes or their regulatory traits. Within a joint project with a group from the University of Hamburg (Germany), we have approached the comparative study of the structural and regulatory lipase system in the closely related species Fusarium verticilloides, Fusarium oxysporum and Fusarium graminearum. 

Moreover, polygalacturonase are responsible for depolymerizing pectin, a major component of the primary plant cell walls. Among them, the endopolygalacturonases (endoPGs) have received major attention, due to their high induction by pectic substrates and to their ability for macerate plant tissue. The F. oxysporum genome contains at least ten different genes rencoding PGs, four of which code for exoPGs and six for endoPGs (one gene being present in four copies on dispensable chromosomes). The expression profile during tomato plant infection revealed maximal induction of two genes, pg1 and pgx6, early after inoculation. Our goal is to identify the mechanism of regulation of the expression pattern of these genes and to clarify their role in the processes of colonization and development of the vascular wilt caused by F. oxysporum. We also intend to analyze the defense response of the host Solanum lycopersicum, in particular the induction of genes encoding Polygalacturonase Inhibiting Proteins (PGIPs) in response to different PG versions (mutant or wild type strains) of Fusarium oxysporum f. sp. lycopersici

Cell wall biosynthesis and remodelling involves a large number of biosynthetic pathways and the concerted action of hundreds of structural genes such as chitin and glucan synthases, glucanosyl transferases, glucosyl hydrolases, chitinases and glucanases. While there is a large number of genetic and biochemical studies on the cell wall biosynthetic enzymes, there is only limited information on the enzymes responsible for crosslinking of the cell wall polymers.  In the rice pathogen Magnaporthe oryzae, the zinc finger protein Con7 regulates virulence and morphogenesis by controlling the expression of cell wall genes such as chitin synthase, chitinase, chitin-binding protein, glucanase and glucanosyl transferase. In F. oxysporum we have identified three orthologous genes. One, designated con7-1 is a single copy gene, while con7-21 and con7-22 are located in a duplicated genomic region. We have generated knockout mutants in con7-1 and double knockouts in con7-21 and con7-22. ?con7-1 strains are unable to infect tomato plants and show striking alterations in colony growth, suggesting that Con7 is a master regulator of morphogenesis and pathogenesis in F. oxysporum. On the other hand, transcription of con7-1 revealed differential processing of the first and second introns resulting in 4 types of mRNA with different abundance, encoding versions of the protein that differ in the presence of putative phosphorylation sites.