Structural requirements of endopolygalacturonase for the interaction with PGIP (polygalacturonase-inhibiting protein)

To invade a plant tissue, phytopathogenic fungi produce several cell wall-degrading enzymes; among them, endopolygalacturonase (PG) catalyzes the fragmentation and solubilization of homogalacturonan. Polygalacturonase-inhibiting proteins (PGIPs), found in the cell wall of many plants, counteract fungal PGs by forming specific complexes with them. We report the crystal structure at 1.73 Å resolution of PG from the phytopathogenic fungus Fusarium moniliforme (FmPG). The structure of FmPG was useful to study the mode of interaction of the enzyme with PGIP-2 from Phaseolus vulgaris. Several amino acids of FmPG were mutated, and their contribution to the formation of the complex with PGIP-2 was investigated by surface plasmon resonance. The residues Lys-269 and Arg-267, located inside the active site cleft, and His-188, at the edge of the active site cleft, are critical for the formation of the complex, which is consistent with the observed competitive inhibition of the enzyme played by PGIP-2. The replacement of His-188 with a proline or the insertion of a tryptophan after position 270, variations that both occur in plant PGs, interferes with the formation of the complex. We suggest that these variations are important structural requirements of plant PGs to prevent PGIP binding

MAPPING AND FUNCTIONAL ANALYSIS OF FOUR APPLE RECEPTOR-LIKE PROTEIN KINASES RELATED TO LRPKM1 IN HCRVF2-TRANSGENIC AND WILD-TYPE APPLE PLANTS

none9mixedV. COVA; R. PARIS; S. PASSEROTTI; E. ZINI; C. GESSLER; I. PERTOT; LOI, Nazia; MUSETTI, Rita; M. KOMJANCV., Cova; R., Paris; S., Passerotti; E., Zini; C., Gessler; I., Pertot; Loi, Nazia; Musetti, Rita; M., Komjan

The genome of the domesticated apple (Malus x domestica Borkh.)

We report a high-quality draft genome sequence of the domesticated apple (Malus x domestica). We show that a relatively recent (> 50 million years ago) genome-wide duplication (GWD) has resulted in the transition from nine ancestral chromosomes to 17 chromosomes in the Pyreae. Traces of older GWDs partly support the monophyly of the ancestral paleohexaploidy of eudicots. Phylogenetic reconstruction of Pyreae and the genus Malus, relative to major Rosaceae taxa, identified the progenitor of the cultivated apple as M. sieversii. Expansion of gene families reported to be involved in fruit development may explain formation of the pome, a Pyreae-specific false fruit that develops by proliferation of the basal part of the sepals, the receptacle. In apple, a subclade of MADS-box genes, normally involved in flower and fruit development, is expanded to include 15 members, as are other gene families involved in Rosaceae-specific metabolism, such as transport and assimilation of sorbitol