Cloning of a Pectate Lyase Gene from Xanthomonas campestris pv. malvacearum and Comparison of Its Sequence Relationship with pel Genes of Soft-Rot Erwinia and Pseudomonas. Ching Hsing Liao. Eastern Regional Research Center, USDA-ARS, Philadelphia, PA 19118, U.S.A. Thomas D. Gaffney (2), Sean P. Bradley(3), and Lee-Jun C.Wong(3). (2) CIBA-GEIGY Corp., Research Triangle Park, NC 27709-22572, U.S.A. and (3) Department of Biological Sciences, University of Massachusetts, Lowell 01854, U.S.A. MPMI 9:14-21. Accepted 25 September 1995, This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1996.

The cotton blight pathogen, Xanthomonas campestris pv. malvacearum strain B414, produces an extracellular pectate lyase (Pel) with an estimated Mr of 41,000 and pi of 9.7. The gene coding for this enzyme initially identified in a 1.8-kb Pst! genomic DNA fragment was cloned. The nucleotide sequences of this 1.8-kb fragment and two pel genes previously cloned from Pseudomonas fluorescens and P. viridiflava were determined. These pel genes encoded pre-Pel proteins consisting of 377 to 380 amino acids (a.a.). A signal peptide consisting of 26 to 29 a.a. was present at the amino-terminus of each pre-Pel. Multiple sequence analysis revealed that Pel proteins of non-Erwinia phytopathogens including Xanlhomonas, Pseudomonas, and Bacillus constituted a distinct cluster, which showed 20 to 43% a.a. identity to the four established Pel families of Erwinia. Homologous pel sequences were detected in various pathovars or strains of X. campestris. AH of these xanthomonads produced an alkaline Pel and were capable of causing soft-rot in potato tuber slices and green pepper fruits.