Diverse evolutionary mechanisms shape the type III effector virulence factor repertoire in the plant pathogen Pseudomonas syringae

被引:85
作者
Rohmer, L
Guttman, DS
Dangl, JL
机构
[1] Univ N Carolina, Dept Biol, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Curriculum Genet, Dept Microbiol & Immunol, Chapel Hill, NC 27599 USA
[3] Univ N Carolina, Carolina Ctr Genome Sci, Chapel Hill, NC 27599 USA
[4] Univ Toronto, Dept Bot, Toronto, ON M5S 3B2, Canada
关键词
D O I
10.1534/genetics.103.019638
中图分类号
Q3 [遗传学];
学科分类号
071007 ; 090102 ;
摘要
Many gram-negative pathogenic bacteria directly translocate effector proteins into eukaryotic host cells via type III delivery systems. Type III effector proteins are determinants of virulence on susceptible plant hosts; they are also the proteins that trigger specific disease resistance in resistant plant hosts. Evolution of type III effectors is dominated by competing forces: the likely requirement for conservation of virulence function, the avoidance of host defenses, and possible adaptation to new hosts. To understand the evolutionary history of type III effectors in Pseudomonas syringae, we searched for homologs to 44 known or candidate P. syringae type III effectors and two effector chaperones. We examined 24 gene families for distribution among bacterial species, amino acid sequence diversity, and features indicative of horizontal transfer. We assessed the role of diversifying and purifying selection in the evolution of these gene families. While some P. syringae type III effectors were acquired recently, others have evolved predominantly by descent. The majority of codons in most of these genes were subjected to purifying selection, suggesting selective pressure to maintain presumed virulence function. However, members of 7 families had domains subject to diversifying selection.
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页码:1341 / 1360
页数:20
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