Search Menu Abstract Sugar cane Saccharum spp. In experiment 1 the bacteria were inoculated into a modified, low sucrose MS medium within which micropropagated plantlets were rooted. After 10 d there was extensive anatomical evidence of endophytic colonization by G. The identity of the bacteria was confirmed by immunogold labelling with an antibody raised against G. A localized host defence response in the form of fibrillar material surrounding the bacteria was associated with both the stem and leaf invasion.

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Correspondence to: Ariel D. Abstract A new role for the plant growth-promoting nitrogen-fixing endophytic bacteria Gluconacetobacter diazotrophicus has been identified and characterized while it is involved in the sugarcane-Xanthomonas albilineans pathogenic interactions.

Living G. Results point toward a form of induction of systemic resistance in sugarcane-G. Key Words: Gluconacetobacter diazotrophicus, elicitors, sugarcane, Xanthomonas albilineans Introduction Sugarcane is an economically important monocotyledon with a unique capacity of accumulating high amounts of sucrose in its stems.

It belongs to the grass family Poaceae , like rice, maize, wheat and sorghum. Sugarcane can specifically interact with Gluconacetobacter diazotrophicus, a nitrogen-fixing bacterium. Primary experiments to find out which plant molecular mechanisms are involved in this interaction were performed, by searching for ESTs that are preferentially or exclusively represented in cDNA libraries from plants inoculated with G. The results reported suggest that the plant is actively involved in the interaction.

SP with G. Extracellular matrix is accumulated around bacterial cells in the protoxylem and xylem parenchyma. All these considerations taken together suggest that G. To support this hypothesis, a genomic study of the interaction sugarcane-Gluconacetobacter diazotrophicus- Xanthomonas albilineans is conducted for the first time.

A differentially-expressed transcript profile has been identified during this complex interaction; moreover, an elicitation of plant defense mechanism against pathogenic bacteria has been demonstrated. By using the sugarcane-diazotrophic bacteria interaction as a model, this article tries to enlighten the role of endophytic organisms in plant defense response.

Materials and Methods Plant materials. Sugarcane plantlets cv. SP free of microorganisms were obtained by sterile meristem culture and micropropagated according to the method of Hendre et al. Vigorous and pathogen-free plants 15 days old after subcultures were selected for experiments. Bacterial cultures and plant infection. Both strains proceeded from the microorganism collection of the National Institute for Sugarcane Research, Havana, Cuba. For mechanical infection, roots, stems and apical meristems of sugarcane plants, grown in greenhouse, were carefully and superficially wounded, by surgical blades previously immersed in separated bacteria cell suspension of G.

After a 30 minutes of water stress, plants were immersed for 15 minutes into the respective bacteria culture. Characterization of the biological activity.

Micropropagated sugarcane plants were both rooted and infested with G. Time between infections was seven days. After the cross infection, plants were maintained in vessels containing a mixture of sterile soil:vermiculite at greenhouse conditions.

A total of 30 plants were considered per experimental treatment as it follows: 1. Before their use, cell debris was suspended in 1 mL of sterile distilled water. For treatments 7 and 8, mL of sugarcane micropropagation media was inoculated with 1mL of bacterial suspension of G. Bacterial detection by polymerase chain reaction.

For a period of 60 days, an assessment of bacterial incidence both X. For treatments 1—6, 1 gr of leaf tissues from five sugarcane plants were macerated in 2mL of distilled sterile water. For treatments 7 and 8, 1 mL of cultures was reinoculated to the respective bacteria medium for 24 h in the same previously described conditions.

Detection of albicidin alb gene expression from X. All PCR products were submitted to electrophoresis in 1. Characterization of the plant genomic response. Experiments were conducted in greenhouse conditions by using ex vitro rooted plants.

Plants were maintained in containers with a 0. Design was as it follows: Treatment I G. A total of 30 sugarcane plants cv. SP were firstly infected with G. Treatment II X.

SP were firstly infected with the pathogen m and after seven days with symbiotic bacteria G. For genomic analysis, five plants per treatment were mixed and considered as a unique sample at T0 immediately after cross infection , T1, T2 and T3 time one, three and seven days after cross infection , respectively.

Approximately mg of leaf tissues per treatment was harvested and immediately frozen in liquid N2.


Gluconacetobacter diazotrophicus

With the sequenced genome available to researchers, new strides have been made in understanding the many processes of G. Recently, with the aid of the sequenced Pal5 genome, a putative FeSII coding gene was identified which opened the possibility of G. However, oxygen is not the only inhibitor of nitrogenase, reactive oxygen species ROS , by-products of aerobic metabolism critical in the production of ATP for the high energy-demanding process of nitrogen fixation, have also proven to be inhibitors of nitrogenase [ 37 , 93 ]. While ROS levels were expected to increase during nitrogen fixation and elevated aerobic respiration, they in fact decreased within G. Asparagine, important to microbial growth promotion, is also a nitrogenase inhibitor and has been found in high amounts in many of G. Genome sequencing has shown that G. Regarding biological nitrogen fixation, the recent sequenced genome corroborates with previous findings which have characterized the major cluster and associated genes of nitrogenase [ 95 , 96 ].







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