Affiliation:
1. Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
Abstract
ABSTRACT
Agrobacterium tumefaciens
is a rod-shaped Gram-negative bacterium that elongates by unipolar addition of new cell envelope material. Approaching cell division, the growth pole transitions to a nongrowing old pole, and the division site creates new growth poles in sibling cells. The
A. tumefaciens
homolog of the
Caulobacter crescentus
polar organizing protein PopZ localizes specifically to growth poles. In contrast, the
A. tumefaciens
homolog of the
C. crescentus
polar organelle development protein PodJ localizes to the old pole early in the cell cycle and accumulates at the growth pole as the cell cycle proceeds. FtsA and FtsZ also localize to the growth pole for most of the cell cycle prior to Z-ring formation. To further characterize the function of polar localizing proteins, we created a deletion of
A. tumefaciens
podJ
(
podJ
At
). Δ
podJ
At
cells display ectopic growth poles (branching), growth poles that fail to transition to an old pole, and elongated cells that fail to divide. In Δ
podJ
At
cells,
A. tumefaciens
PopZ-green fluorescent protein (PopZ
At
-GFP) persists at nontransitioning growth poles postdivision and also localizes to ectopic growth poles, as expected for a growth-pole-specific factor. Even though GFP-PodJ
At
does not localize to the midcell in the wild type, deletion of
podJ
At
impacts localization, stability, and function of Z-rings as assayed by localization of FtsA-GFP and FtsZ-GFP. Z-ring defects are further evidenced by minicell production. Together, these data indicate that PodJ
At
is a critical factor for polar growth and that Δ
podJ
At
cells display a cell division phenotype, likely because the growth pole cannot transition to an old pole.
IMPORTANCE
How rod-shaped prokaryotes develop and maintain shape is complicated by the fact that at least two distinct species-specific growth modes exist: uniform sidewall insertion of cell envelope material, characterized in model organisms such as
Escherichia coli
, and unipolar growth, which occurs in several alphaproteobacteria, including
Agrobacterium tumefaciens
. Essential components for unipolar growth are largely uncharacterized, and the mechanism constraining growth to one pole of a wild-type cell is unknown. Here, we report that the deletion of a polar development gene,
podJ
At
, results in cells exhibiting ectopic polar growth, including multiple growth poles and aberrant localization of cell division and polar growth-associated proteins. These data suggest that PodJ
At
is a critical factor in normal polar growth and impacts cell division in
A. tumefaciens
.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
22 articles.
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