The Calmodulin-Binding Transcription Factor OsCBT Suppresses Defense Responses to Pathogens in Rice

Abstract

We previously isolated the OsCBT gene, which encodes a calmodulin (CaM)-binding protein, from a rice expression library constructed from fungal elicitor-treated rice suspension cells. In order to understand the function of OsCBT in rice, we isolated and characterized a T-DNA insertion mutant allele named oscbt-1. The oscbt-1 mutant exhibits reduced levels of OsCBT transcripts and no significant morphological changes compared to wild-type plant although the growth of the mutant is stunted. However, oscbt-1 mutants showed significant resistance to two major rice pathogens. The growth of the rice blast fungus Magnaporthe grisea, as well as the bacterial pathogen Xanthomonas oryzae pv. oryzae was significantly suppressed in oscbt-1 plants. Histochemical analysis indicated that the hypersensitive-response was induced in the oscbt-1 mutant in response to compatible strains of fungal pathogens. OsCBT expression was induced upon challenge with fungal elicitor. We also observed significant increase in the level of pathogenesis-related genes in the oscbt-1 mutant even under pathogen-free condition. Taken together, the results support an idea that OsCBT might act as a negative regulator on plant defense.

Calmodulin-binding transcription activators and perspectives for applications in biotechnology

“…OsCBT, a CAMTA member from rice, plays a negative role in regulating rice defenses against both the bacterial pathogen Xanthomonas oryzae pv. oryzae and the rice blast fungus Magnaporthe grisea (Koo et al 2009). In tomato, CAMTA transcription factors, SlSR1 and SlSR3L, also negatively regulate pathogen resistance responses (Li et al 2014).…”

Recent Advances in Calcium/Calmodulin-Mediated Signaling with an Emphasis on Plant-Microbe Interactions

“…Recently, AtSR1/CAMTA3 was also shown to negatively regulate ethylene-mediated senescence by recognizing a CGCG box in the promoters of EIN3 and disease resistance by interacting with a CGCG box in the promoters of NDR1, a key signaling component required for coiled-coil-NB-LRR-type R gene-mediated plant immunity (Nie et al, 2012). Similar to the function of CAMTA3, OsCBT, a CAMTA member from rice, also plays a negative role in regulating rice defense against both the bacterial pathogen Xanthomonas oryzae pv oryzae and the rice blast fungus Magnaporthe grisea (Koo et al, 2009). Very recently, CAMTA3 was shown to play a critical role in plant defense against insect herbivory (Laluk et al, 2012;Qiu et al, 2012).…”

Tomato SR/CAMTA transcription factors SlSR1 and SlSR3L negatively regulate disease resistance response and SlSR1L positively modulates drought stress tolerance

“…Similarly, the rice oscbt mutant exhibited significant resistance to blast fungal pathogen Magnaporthe grisea and leaf blight bacterial pathogen Xanthomonas oryzae pv. oryzae [17]. On the other hand, it was recently shown that the Arabidopsis AtSR1 and AtSR2 also play important roles in regulating tolerance to low temperature [25,26] and drought stress [27].…”