Transcriptional upregulation of four genes of the lysine biosynthetic pathway by homocitrate accumulation in Penicillium chrysogenum: homocitrate as a sensor of lysine-pathway distress

FRANCO TEVES,; MO´ NICA LAMAS-MACEIRAS; CARLOS GARCı´A-ESTRADA; JAVIER CASQUEIRO; LEOPOLDO NARANJO; RICARDO VICENTE ULLA´ N; SCERVINO JOSE M; XIAOBIN WU; TANIA VELASCO-CONDE; JUAN FRANCISCO MARTIN

MICROBIOLOGY-UK

SOC GENERAL MICROBIOLOGY

Lugar: London; Año: 2009 vol. 155 p. 3787 - 3797

1350-0872

The lysine biosynthetic pathway has to supply large amounts of a-aminoadipic acid for penicillinbiosynthesis in Penicillium chrysogenum. In this study, we have characterized the P.chrysogenum L2 mutant, a lysine auxotroph that shows highly increased expression of severallysine biosynthesis genes (lys1, lys2, lys3, lys7). The L2 mutant was found to be deficient inhomoaconitase activity since it was complemented by the Aspergillus nidulans lysF gene. Wehave cloned a gene (named lys3) that complements the L2 mutation by transformation with a P.chrysogenum genomic library, constructed in an autonomous replicating plasmid. The lys3-encoded protein showed high identity to homoaconitases. In addition, we cloned the mutant lys3allele from the L2 strain that showed a G1534 to A1534 point mutation resulting in a Gly495 toAsp495 substitution. This mutation is located in a highly conserved region adjacent to two of thethree cysteine residues that act as ligands to bind the iron–sulfur cluster required forhomoaconitase activity. The L2 mutant accumulates homocitrate. Deletion of the lys1 gene(homocitrate synthase) in the L2 strain prevented homocitrate accumulation and revertedexpression levels of the four lysine biosynthesis genes tested to those of the parental prototrophicstrain. Homocitrate accumulation seems to act as a sensor of lysine-pathway distress, triggeringoverexpression of four of the lysine biosynthesis genes.