Xanthomonas campestris attenuates virulence by sensing light through a bacteriophytochrome photoreceptor.
Phytochromes constitute a major photoreceptor family found in plants, algae, fungi, and prokaryotes, including pathogens. Here, we report that Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot disease which affects cruciferous crops worldwide, codes for a functional bacteriophytochrome (XccBphP). XccBphP possesses an N-terminal PAS2-GAF-PHY photosensory domain triad and a C-terminal PAS9 domain as its output module. Our results show that illumination of Xcc, prior to plant infection, attenuates its virulence in an XccBphP-dependent manner. Moreover, in response to light, XccBphP downregulates xanthan exopolysaccharide production and biofilm formation, two known Xcc virulence factors. Furthermore, the XccbphP null mutant shows enhanced virulence, similar to that of dark-adapted Xcc cultures. Stomatal aperture regulation and callose deposition, both well-established plant defense mechanisms against bacterial pathogens, are overridden by the XccbphP strain. Additionally, an RNA-Seq analysis reveals that far-red light or XccBphP overexpression produces genomewide transcriptional changes, including the inhibition of several Xcc virulence systems. Our findings indicate that Xcc senses light through XccBphP, eliciting bacterial virulence attenuation via downregulation of bacterial virulence factors. The capacity of XccBphP to respond to light both in vitro and in vivo was abolished by a mutation on the conserved Cys13 residue. These results provide evidence for a novel bacteriophytochrome function affecting an infectious process.
Fundación Instituto Leloir - IIBBA CONICET, Buenos Aires, Argentina hbonomi@leloir.org.ar avojnov@fundacioncassara.org.ar fmalamud@iibintech.com.ar.
Hernán R
0000-0002-1550-6181
HR
Bonomi
Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Buenos Aires, Argentina.
Laila
L
Toum
Fundación Instituto Leloir - IIBBA CONICET, Buenos Aires, Argentina.
Gabriela
G
Sycz
Fundación Instituto Leloir - IIBBA CONICET, Buenos Aires, Argentina.
Rodrigo
R
Sieira
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Andrés M
AM
Toscani
Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Buenos Aires, Argentina.
Gustavo E
GE
Gudesblat
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Federico C
FC
Leskow
Fundación Instituto Leloir - IIBBA CONICET, Buenos Aires, Argentina.
Fernando A
FA
Goldbaum
Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Buenos Aires, Argentina hbonomi@leloir.org.ar avojnov@fundacioncassara.org.ar fmalamud@iibintech.com.ar.
Adrián A
AA
Vojnov
Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Buenos Aires, Argentina hbonomi@leloir.org.ar avojnov@fundacioncassara.org.ar fmalamud@iibintech.com.ar.|UNSAM Campus Miguelete IIB - Instituto de Investigaciones Biotecnológicas, Buenos Aires, Argentina.
Florencia
F
Malamud
D001426:Bacterial Proteins / Q000235:genetics*; D018441:Biofilms / Q000254:growth & development; D018556:Crops, Agricultural; D015964:Gene Expression Regulation, Bacterial; D059014:High-Throughput Nucleotide Sequencing; D008027:Light; D009154:Mutation; D010834:Phytochrome / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics; D016959:Xanthomonas campestris / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*
D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D037521:Virulence Factors; D010834:Phytochrome; C002563:xanthan gum
bathy‐type phytochrome; infection; plant defenses; transcriptional regulation; virulence factors