Carbon catabolite repression(CCR),which is mainly mediated by Cre1 and triggered by glucose,leads to a decrease in cellulase production in Trichoderma reesei.Many studies have focused on modifying Cre1 for alleviating...Carbon catabolite repression(CCR),which is mainly mediated by Cre1 and triggered by glucose,leads to a decrease in cellulase production in Trichoderma reesei.Many studies have focused on modifying Cre1 for alleviating CCR.Based on the homologous alignment of CreA from wild-type Penicillium oxalicum 114–2(Po-0)and cellulase hyperproducer JUA10-1(Po-1),we constructed a C-terminus substitution strain—Po-2—with decreased transcriptional levels of cellulase and enhanced CCR.Results revealed that the C-terminal domain of CreAPo−1 plays an important role in alleviating CCR.Furthermore,we replaced the C-terminus of Cre1 with that of CreAPo−1 in T.reesei(Tr-0)and generated Tr-1.As a control,the C-terminus of Cre1 was truncated and Tr-2 was generated.The transcriptional profiles of these transformants revealed that the C-terminal chimera greatly improves cellulase transcription in the presence of glucose and thus upregulates cellulase in the presence of glucose and weakens CCR,consistent with truncating the C-terminus of Cre1 in Tr-0.Therefore,we propose constructing a C-terminal chimera as a new strategy to improve cellulase production and alleviate CCR in the presence of glucose.展开更多
Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides （LCOs）. Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation....Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides （LCOs）. Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accu- mulation and subsequent signaling are an integral part of rhizobium LCO signaling remains elusive. Here, we show that cytokinin signaling is required for the majority of transcriptional changes induced by rhizo- bium LCOs. In addition, we demonstrate that several cytokinins accumulate in the root susceptible zone 3 h after rhizobium LCO application, including the biologically most active cytokinins, trans-zeatin and iso- pentenyl adenine. These responses are dependent on calcium- and calmodulin-dependent protein kinase （CCaMK）, a key protein in rhizobial LCO-induced signaling. Analysis of the ethylene-insensitive Mtein21 Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signaling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.展开更多
基金This work was supported by National Key R&D Program of China(No.2018YFA0901700)National Natural Science Foundation of China(No.31870785 and 31570040)+1 种基金the 111 Project(No.B16030)the State Key Laboratory of Microbial Technology Open Projects Fund.
文摘Carbon catabolite repression(CCR),which is mainly mediated by Cre1 and triggered by glucose,leads to a decrease in cellulase production in Trichoderma reesei.Many studies have focused on modifying Cre1 for alleviating CCR.Based on the homologous alignment of CreA from wild-type Penicillium oxalicum 114–2(Po-0)and cellulase hyperproducer JUA10-1(Po-1),we constructed a C-terminus substitution strain—Po-2—with decreased transcriptional levels of cellulase and enhanced CCR.Results revealed that the C-terminal domain of CreAPo−1 plays an important role in alleviating CCR.Furthermore,we replaced the C-terminus of Cre1 with that of CreAPo−1 in T.reesei(Tr-0)and generated Tr-1.As a control,the C-terminus of Cre1 was truncated and Tr-2 was generated.The transcriptional profiles of these transformants revealed that the C-terminal chimera greatly improves cellulase transcription in the presence of glucose and thus upregulates cellulase in the presence of glucose and weakens CCR,consistent with truncating the C-terminus of Cre1 in Tr-0.Therefore,we propose constructing a C-terminal chimera as a new strategy to improve cellulase production and alleviate CCR in the presence of glucose.
文摘Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides （LCOs）. Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accu- mulation and subsequent signaling are an integral part of rhizobium LCO signaling remains elusive. Here, we show that cytokinin signaling is required for the majority of transcriptional changes induced by rhizo- bium LCOs. In addition, we demonstrate that several cytokinins accumulate in the root susceptible zone 3 h after rhizobium LCO application, including the biologically most active cytokinins, trans-zeatin and iso- pentenyl adenine. These responses are dependent on calcium- and calmodulin-dependent protein kinase （CCaMK）, a key protein in rhizobial LCO-induced signaling. Analysis of the ethylene-insensitive Mtein21 Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signaling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.
