Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 7, 1999
Publication Date: N/A
The population dynamics of mutants of P. syringae B728a bearing defects in genes that function at different levels in the gacS regulon were examined in the field. Growth of the non-lesion forming gacS (global activator sensor kinase) and salA (regulated by GacS) mutants were similar to B728a in laboratory leaf infiltration assays. However, in the field, population sizes of the gacS and salA mutants were on average (from plant emergence to 63 DAP) 100- and 5-fold less than wild type, respectively. Population sizes of the salA mutant were more nearly similar to B728a than to the gacS mutant in spite of the mutant's impaired ability to cause disease. The subset of genes in the gacS regulon that are not regulated by SalA appears to have a major role in growth/survival of B728a in the field. SalA regulates expression of syrB (syringomycin biosynthetic gene). Population sizes of a syrB mutant were intermediate between those of the salA mutant and B728a. Hence, syringomycin appeared to contribute, in part, to the decreased population sizes of the salA mutant.