The lemA gene required for pathogenicity of Pseudomonas syringae pv. syringae on bean is a member of a family of two-component regulators

Abstract

The lemA gene of the plant pathogen Pseudomonas syringae pv. syringae is required for disease lesion formation on bean plants. Cosmid clones that complemented a lemA mutant in trans were isolated previously. The lemA gene was localized by subcloning and transposon mutagenesis. The lemA region and flanking DNA were sequenced, and an open reading frame of 2.7 kb was identified. The nucleotide and predicted amino acid sequences of the kmA gene showed sequence similarity to a family of prokaryotic two-component regulatory proteins. Unlike most of the previously described two-component systems, the lemA gene product contained homology to both components in one protein. Pseudomonas syringae pv. syringae isolate B728a is a causal agent of bacterial brown spot of bean (Phaseolus vulgaris). To identify bacterial genes necessary for disease development, prototrophic Tn5 mutants of isolate B728a were screened on bean pods for loss of the typical pathogenic response. One mutant, NPS3136, has lost the ability to form brown spot lesions on bean leaves and pods (55). This lemA (lesion manifestation) mutant retains the ability to grow on and colonize bean plants and to elicit a hypersensitive reaction on nonhosts (55). The phenotype of a lemA mutant is significantly different from the phenotype of another class of nonpathogenic mutants, the hrp mutants, which are affected both in their colonization of and pathogenic interaction with host plants and in their ability to elicit a hypersensitive reaction on nonhost plants (for a review, see reference 56). Further characterization of the lemA mutant revealed that it was also deficient in the ability to produce protease and the toxin syringomycin (19,20). This pleiotropic phenotype suggested that the lemA gene might encode a regulatory molecule. In this report, we describe further characterization of the lemA gene of P. syringae pv. syringae by subcloning, transposon mutagenesis, and DNA sequence analysis. We present evidence that the lemA gene has similarity to the conserved domains within both the HPK and the RR proteins in a family of prokaryotic two-component regulatory proteins. MATERIALS AND METHODSBacterial strains, plasmids, and growth conditions. The bacterial strains and plasmids used in this work are listed in

Surface motility in Pseudomonas sp. DSS73 is required for efficient biological containment of the root-pathogenic microfungi Rhizoctonia solani and Pythium ultimum

“…In addition, surface motility could be restored in the gacS mutant upon introduction of pEMH97 encoding the heterologous wild-type gacS gene from Pseudomonas syringae pv. syringae (Hrabak & Willis, 1992), supporting the finding of Koch et al (2002) that amphisin synthesis is regulated by gacS (compare Fig.1C and D). and solidified with 0?6 % agar.…”

Cultivation of a human-associated TM7 phylotype reveals a reduced genome and epibiotic parasitic lifestyle

“…We found that despite its relatively small genome, TM7x contains many pathogenesis-related virulence gene homologs, including two virulence islands encoding separate type IV secretion systems and membrane-associated virulence-related proteins, such as OmpA (36) and LemA (37), as well as cholinebinding proteins (38) (Table S2). It is particularly interesting to point out that the TM7x genome contains various ORFs encoding predicted proteins with toxin-antitoxin (TA) domains, such as VapC, VapB, and xenobiotic response element (39), as well as an abortive infection protein homolog known to promote cell death and limit phage replication within a bacterial population (40).…”

The global activator GacA of Pseudomonas aeruginosa PAO positively controls the production of the autoinducer N‐butyryl‐homoserine lactone and the formation of the virulence factors pyocyanin, cyanide, and lipase

“…GacA is part of a two-component system and belongs to the FixJ family of response regulators (Laville et al, 1992). The cognate sensor appears to be the transmembrane protein LemA (Hrabak and Willis, 1992;Rich et al, 1994). Both the gacA and lemA genes are highly conserved in fluorescent pseudomonads (Liao et al, 1994;Corbell and Loper, 1995;Grewal et al, 1995).…”