Arbuscular mycorrhizal fungi and rhizobia are two important plant symbionts. Rhizobia are known f... more Arbuscular mycorrhizal fungi and rhizobia are two important plant symbionts. Rhizobia are known for fixing nitrogen inside legume root nodules while Arbuscular mycorrhizal (AM) fungi provide plants with nutrients and other benefits. AM fungi are ubiquitous soil microorganisms and establish a symbiotic relationship with more than 80% of plant species of natural ecosystems while rhizobia association is more specific and involved almost leguminous plants. The symbiosis between legumes-Rhizobium and arbuscular mycorrhizal fungi (AMF) improves plant growth and tolerance against biotic and abiotic stress. This suggests that it is possible to use rhizobia and mycorrhizal to mitigate detrimental impacts of these stresses on terrestrial ecosystem health and agricultural productivity. This will lead to accelerate the natural process of re-vegetation in decertified semiarid ecosystem. AMF and rhizobia interactions in legumes host are complex and our understanding of their impact on plant growt...
Actinorhizal hosts are non-leguminous perennial plants belonging to 8 angiosperm families. They a... more Actinorhizal hosts are non-leguminous perennial plants belonging to 8 angiosperm families. They are capable of forming root nodules as a result of infection by a nitrogen-fixing actinomycete called Frankia. Actinorhizal nodules consist of multiple lobes, each of which represents a modified lateral root with infected cells in the expanded cortex. This article summarizes the most recent knowledge about this original symbiotic process. The infection process is described both at cytological and molecular levels. The use of transgenic Casuarinaceae for studying in actinorhizal nodules the regulation of several symbiotic promoters from legumes is also discussed. With progress in plant genome sequencing, comparative genomics in legumes and actinorhizal plants should contribute to the understanding of the evolutionary history of nitrogen-fixing symbioses. Key words: Nitrogen-fixation, actinorhizal nodules, Frankia, Casuarina, symbiotic gene.
Comparison of four constitutive promoters for the expression of transgenes in the tropical nitrog... more Comparison of four constitutive promoters for the expression of transgenes in the tropical nitrogen-fixing tree Allocasuarina verticillata
The MtEnod11 gene from Medicago truncatula is widely used as an early infection-related molecular... more The MtEnod11 gene from Medicago truncatula is widely used as an early infection-related molecular marker for endosymbiotic associations involving both rhizobia and arbuscular mycorrhizal fungi. In this article, heterologous expression of the MtEnod11 promoter has been studied in two actinorhizal trees, Casuarina glauca and Allocasuarina verticillata. Transgenic C. glauca and A. verticillata expressing a ProMtEnod11::β-glucuronidase (gus) fusion were generated and the activation of the transgene investigated in the context of the symbiotic associations with the N-fixing actinomycete Frankia and both endo- and ectomycorrhizal fungi (Glomus intraradices and Pisolithus albus, respectively). ProMtEnod11::gus expression was observed in root hairs, prenodules, and nodules and could be correlated with the infection of plant cells by Frankia spp. However, no activation of the gus reporter gene was detected prior to infection or in response to either rhizobial Nod factors or the wasp venom pe...
Actinorhizal plants are able to establish a symbiotic relationship with Frankia bacteria leading ... more Actinorhizal plants are able to establish a symbiotic relationship with Frankia bacteria leading to the formation of root nodules. The symbiotic interaction starts with the exchange of symbiotic signals in the soil between the plant and the bacteria. This molecular dialog involves signaling molecules that are responsible for the specific recognition of the plant host and its endosymbiont. Here we studied two factors potentially involved in signaling between Frankia casuarinae and its actinorhizal host Casuarina glauca: (1) the Root Hair Deforming Factor (CgRHDF) detected using a test based on the characteristic deformation of C. glauca root hairs inoculated with F. casuarinae and (2) a NIN activating factor (CgNINA) which is able to activate the expression of CgNIN, a symbiotic gene expressed during preinfection stages of root hair development. We showed that CgRHDF and CgNINA corresponded to small thermoresistant molecules. Both factors were also hydrophilic and resistant to a chit...
The MYB gene family constitutes one of the largest transcription factors (TFs) modulating various... more The MYB gene family constitutes one of the largest transcription factors (TFs) modulating various biological processes in plants. Although genome-wide analysis of this gene family has been carried out in some species, only three MYB members have been functionally characterized heretofore in sesame (Sesamum indicum L.). Here, we identified a relatively high number (287) of sesame MYB genes (SIMYBs) with an uncommon overrepresentation of the 1R-subfamily. A total of 95% of SIMYBs was mapped unevenly onto the 16 linkage groups of the sesame genome with 55 SIMYBs tandemly duplicated. In addition, molecular characterization, gene structure, and evolutionary relationships of SIMYBs were established. Based on the close relationship between sesame and Arabidopsis thaliana, we uncovered that the functions of SIMYBs are highly diverse. A total of 65% of SIMYBs were commonly detected in five tissues, suggesting that they represent key TFs modulating sesame growth and development. Moreover, we ...
ABSTRACT Cheverry, J. L., Sy, M. O., Pouliquen, J. and Marcellin, P. 1988. Regulation by CO2 of 1... more ABSTRACT Cheverry, J. L., Sy, M. O., Pouliquen, J. and Marcellin, P. 1988. Regulation by CO2 of 1-aminocyclopropane-1-carboxylic acid conversion to ethylene in climateric fruits. - Physiol. Plant. 72: 535–540.A high CO2 concentration (20%) at 20°C rapidly and strongly inhibited the development of the climacteric ethylene burst in apple (Malus domestica Borkh. cv. Granny Smith) and avocado (Persea americana Mill. cv. Fuerte) fruits and did not change 1-aminocyclopropane-l-carboxylic acid (ACC) content. Treatment with 20% CO2 markedly decreased ACC-dependent ethylene biosynthesis at 20°C in climacteric pericarp tissues. It is suggested, therefore, that high CO2 levels inhibit conversion of ACC to ethylene.Synthesis of the ethylene forming enzyme (EFE) was enhanced when intact preclimacteric apples or early climacteric avocados were pretreated for 40 h with 10 μ11-1 ethylene. When CO2 (20%) and ethylene were both applied, a reduced stimulatory effect of ethylene on EFE synthesis was observed. A high CO2 concentration enhanced EFE acivity in excised tissues of apples and avocados incubated with ACC (2 mM) and cycloheximide (1 mM) or 2–5-norbornadiene (5 ml 1-1). In the autocatalytic process, 20% CO2 antagonized the stimulation of EFE synthesis by ethylene, but promoted EFE activity.
Arbuscular mycorrhizal fungi and rhizobia are two important plant symbionts. Rhizobia are known f... more Arbuscular mycorrhizal fungi and rhizobia are two important plant symbionts. Rhizobia are known for fixing nitrogen inside legume root nodules while Arbuscular mycorrhizal (AM) fungi provide plants with nutrients and other benefits. AM fungi are ubiquitous soil microorganisms and establish a symbiotic relationship with more than 80% of plant species of natural ecosystems while rhizobia association is more specific and involved almost leguminous plants. The symbiosis between legumes-Rhizobium and arbuscular mycorrhizal fungi (AMF) improves plant growth and tolerance against biotic and abiotic stress. This suggests that it is possible to use rhizobia and mycorrhizal to mitigate detrimental impacts of these stresses on terrestrial ecosystem health and agricultural productivity. This will lead to accelerate the natural process of re-vegetation in decertified semiarid ecosystem. AMF and rhizobia interactions in legumes host are complex and our understanding of their impact on plant growt...
Actinorhizal hosts are non-leguminous perennial plants belonging to 8 angiosperm families. They a... more Actinorhizal hosts are non-leguminous perennial plants belonging to 8 angiosperm families. They are capable of forming root nodules as a result of infection by a nitrogen-fixing actinomycete called Frankia. Actinorhizal nodules consist of multiple lobes, each of which represents a modified lateral root with infected cells in the expanded cortex. This article summarizes the most recent knowledge about this original symbiotic process. The infection process is described both at cytological and molecular levels. The use of transgenic Casuarinaceae for studying in actinorhizal nodules the regulation of several symbiotic promoters from legumes is also discussed. With progress in plant genome sequencing, comparative genomics in legumes and actinorhizal plants should contribute to the understanding of the evolutionary history of nitrogen-fixing symbioses. Key words: Nitrogen-fixation, actinorhizal nodules, Frankia, Casuarina, symbiotic gene.
Comparison of four constitutive promoters for the expression of transgenes in the tropical nitrog... more Comparison of four constitutive promoters for the expression of transgenes in the tropical nitrogen-fixing tree Allocasuarina verticillata
The MtEnod11 gene from Medicago truncatula is widely used as an early infection-related molecular... more The MtEnod11 gene from Medicago truncatula is widely used as an early infection-related molecular marker for endosymbiotic associations involving both rhizobia and arbuscular mycorrhizal fungi. In this article, heterologous expression of the MtEnod11 promoter has been studied in two actinorhizal trees, Casuarina glauca and Allocasuarina verticillata. Transgenic C. glauca and A. verticillata expressing a ProMtEnod11::β-glucuronidase (gus) fusion were generated and the activation of the transgene investigated in the context of the symbiotic associations with the N-fixing actinomycete Frankia and both endo- and ectomycorrhizal fungi (Glomus intraradices and Pisolithus albus, respectively). ProMtEnod11::gus expression was observed in root hairs, prenodules, and nodules and could be correlated with the infection of plant cells by Frankia spp. However, no activation of the gus reporter gene was detected prior to infection or in response to either rhizobial Nod factors or the wasp venom pe...
Actinorhizal plants are able to establish a symbiotic relationship with Frankia bacteria leading ... more Actinorhizal plants are able to establish a symbiotic relationship with Frankia bacteria leading to the formation of root nodules. The symbiotic interaction starts with the exchange of symbiotic signals in the soil between the plant and the bacteria. This molecular dialog involves signaling molecules that are responsible for the specific recognition of the plant host and its endosymbiont. Here we studied two factors potentially involved in signaling between Frankia casuarinae and its actinorhizal host Casuarina glauca: (1) the Root Hair Deforming Factor (CgRHDF) detected using a test based on the characteristic deformation of C. glauca root hairs inoculated with F. casuarinae and (2) a NIN activating factor (CgNINA) which is able to activate the expression of CgNIN, a symbiotic gene expressed during preinfection stages of root hair development. We showed that CgRHDF and CgNINA corresponded to small thermoresistant molecules. Both factors were also hydrophilic and resistant to a chit...
The MYB gene family constitutes one of the largest transcription factors (TFs) modulating various... more The MYB gene family constitutes one of the largest transcription factors (TFs) modulating various biological processes in plants. Although genome-wide analysis of this gene family has been carried out in some species, only three MYB members have been functionally characterized heretofore in sesame (Sesamum indicum L.). Here, we identified a relatively high number (287) of sesame MYB genes (SIMYBs) with an uncommon overrepresentation of the 1R-subfamily. A total of 95% of SIMYBs was mapped unevenly onto the 16 linkage groups of the sesame genome with 55 SIMYBs tandemly duplicated. In addition, molecular characterization, gene structure, and evolutionary relationships of SIMYBs were established. Based on the close relationship between sesame and Arabidopsis thaliana, we uncovered that the functions of SIMYBs are highly diverse. A total of 65% of SIMYBs were commonly detected in five tissues, suggesting that they represent key TFs modulating sesame growth and development. Moreover, we ...
ABSTRACT Cheverry, J. L., Sy, M. O., Pouliquen, J. and Marcellin, P. 1988. Regulation by CO2 of 1... more ABSTRACT Cheverry, J. L., Sy, M. O., Pouliquen, J. and Marcellin, P. 1988. Regulation by CO2 of 1-aminocyclopropane-1-carboxylic acid conversion to ethylene in climateric fruits. - Physiol. Plant. 72: 535–540.A high CO2 concentration (20%) at 20°C rapidly and strongly inhibited the development of the climacteric ethylene burst in apple (Malus domestica Borkh. cv. Granny Smith) and avocado (Persea americana Mill. cv. Fuerte) fruits and did not change 1-aminocyclopropane-l-carboxylic acid (ACC) content. Treatment with 20% CO2 markedly decreased ACC-dependent ethylene biosynthesis at 20°C in climacteric pericarp tissues. It is suggested, therefore, that high CO2 levels inhibit conversion of ACC to ethylene.Synthesis of the ethylene forming enzyme (EFE) was enhanced when intact preclimacteric apples or early climacteric avocados were pretreated for 40 h with 10 μ11-1 ethylene. When CO2 (20%) and ethylene were both applied, a reduced stimulatory effect of ethylene on EFE synthesis was observed. A high CO2 concentration enhanced EFE acivity in excised tissues of apples and avocados incubated with ACC (2 mM) and cycloheximide (1 mM) or 2–5-norbornadiene (5 ml 1-1). In the autocatalytic process, 20% CO2 antagonized the stimulation of EFE synthesis by ethylene, but promoted EFE activity.
Uploads
Papers by Mame-oureye Sy