GBF 1 differentially regulates CAT 2 and PAD 4 transcription to promote pathogen defense in Arabidopsis thaliana

• Published in: The Plant journal : for cell and molecular biology Vol. 91; no. 5; pp. 802 - 815
• Main Authors: Giri, Mrunmay K., Singh, Nidhi, Banday, Zeeshan Z., Singh, Vijayata, Ram, Hathi, Singh, Deepjyoti, Chattopadhyay, Sudip, Nandi, Ashis K.
• Format: Journal Article
• Language: English
• Published: 01-09-2017
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13608

G‐
BOX BINDING FACTOR
1 (
GBF
1) influences light‐regulated seedling development in Arabidopsis, and inhibits
CATALASE
2
(
CAT
2
) expression during senescence.
CAT
2 functions as a scavenger of hydrogen peroxide. The role of
GBF
1 in the defense response is not known. We report here that
GBF
1 positively influences the defense against virulent and avirulent strains of
Pseudomonas syringae
. The
gbf1
mutants are susceptible, whereas
GBF
1 over‐expresser transgenic plants are resistant to bacterial pathogens.
GBF
1 negatively regulates pathogen‐induced
CAT
2
expression and thereby positively regulates the hypersensitive response. In addition to
CAT
2
promoter,
GBF
1 binds to the G‐box‐like element present in the intron of
PHYTOALEXIN DEFICIENT
4
(
PAD
4
). This association of
GBF
1 with
PAD
4
intron is enhanced upon pathogenesis.
GBF
1 positively regulates
PAD
4
transcription in an intron‐dependent manner.
GBF
1‐mediated positive regulation of
PAD
4
expression is also evident in
gbf1
mutant and
GBF
1 over‐expression lines. Similar to
pad4
mutants, pathogen‐induced camalexin and salicylic acid (
SA
) accumulation, and expression of
SA
‐inducible
PATHOGENESIS RELATED
1
(
PR
1
) gene are compromised in the
gbf1
mutant. Exogenous application of
SA
rescues the loss‐of‐defense phenotypes of
gbf1
mutant. Thus, altogether, our results demonstrate that
GBF
1 is an important component of the plant defense response that functions upstream of
SA
accumulation and, by oppositely regulating
CAT
2
and
PAD
4
, promotes disease resistance in Arabidopsis.
The function of Arabidopsis
GBF
1 hitherto has been mostly implicated in light‐mediated seedling development. We show that
GBF
1 regulates the expression of
CAT
2
negatively and
PAD
4
positively to control the hypersensitive response, salicylic acid (
SA
) accumulation, and defense against virulent and avirulent strains of bacterial pathogens.