Quantitative Proteomic Analysis of the Interaction Between the Endophytic Plant-Growth-Promoting Bacterium Gluconacetobacter diazotrophicus and Sugarcane

Abstract

Gluconacetobacter diazotrophicus is a plant-growth-promoting bacterium that colonizes sugarcane. In order to investigate molecular aspects of the G. diazotrophicus-sugarcane interaction, we performed a quantitative mass spectrometry-based proteomic analysis by (15)N metabolic labeling of bacteria, root samples, and co-cultures. Overall, more than 400 proteins were analyzed and 78 were differentially expressed between the plant-bacterium interaction model and control cultures. A comparative analysis of the G. diazotrophicus in interaction with two distinct genotypes of sugarcane, SP70-1143 and Chunee, revealed proteins with fundamental roles in cellular recognition. G. diazotrophicus presented proteins involved in adaptation to atypical conditions and signaling systems during the interaction with both genotypes. However, SP70-1143 and Chunee, sugarcane genotypes with high and low contribution of biological nitrogen fixation, showed divergent responses in contact with G. diazotrophicus. The SP70-1143 genotype overexpressed proteins from signaling cascades and one from a lipid metabolism pathway, whereas Chunee differentially synthesized proteins involved in chromatin remodeling and protein degradation pathways. In addition, we have identified 30 bacterial proteins in the roots of the plant samples; from those, nine were specifically induced by plant signals. This is the first quantitative proteomic analysis of a bacterium-plant interaction, which generated insights into early signaling of the G. diazotrophicus-sugarcane interaction.

Endophytic colonization of Arabidopsis thaliana by Gluconacetobacter diazotrophicus and its effect on plant growth promotion, plant physiology, and activation of plant defense

“…During the last decades, several studies have attempted to identify genes and proteins regulated during G. diazotrophicus-plant associations (dos Santos et al 2010;Lery et al 2011;Galisa et al 2012;Bertini et al 2014). However, most of agronomical relevant plants are slow-growing species with a complex genome, and whose large size hinders cultivation under controlled environment, which limits the detailed molecular characterization of plant-bacteria interaction.…”

“…Genomic, transcriptomic, and proteomic analyses have revealed a wide range of plant molecular responses to G. diazotrophicus inoculation in plants (Carvalho et al 2011;Lery et al 2011;Alquéres et al 2013;Vargas et al 2014). However, difficulty on carrying multiple and simultaneous experiments under controlled conditions, during the full life cycle of most host plants, has generated fragmentary comparative data which in turn has impaired rapid understanding and kept relevant questions unclear.…”

“…Gene expression studies have shown that the receptor kinase SHR5 is involved in N 2 fixation in plantendophytic bacteria associations (Vinagre et al 2006). Additionally, quantitative proteomic and transcriptomic analysis of the interaction between sugarcane and G. diazotrophicus has provided insight into the early signaling and initial molecular events that may trigger the increased drought tolerance observed in the host plant (Lery et al 2011;Vargas et al 2014). Glutathione reductase and bacterial superoxide dismutase are known to be crucial for the colonization of rice by G. diazotrophicus (Alquéres et al 2013).…”

Root ethylene signalling is involved in Miscanthus sinensis growth promotion by the bacterial endophyte Herbaspirillum frisingense GSF30T

“…This parallels the observation for the M. sinensis cinnamyl alcohol dehydrogenase after inoculation with H. frisingense . Finally, little similarity in the differential proteomes is apparent in other endophyte-grass responses, such as the sugarcane response to the plant-growth-promoting bacterium G. diazotrophicus after 1 d (Lery et al , 2011). This may partially be due to the fact that different sampling periods were used in the different studies, but as no general clues on plant responses in endophyte–plant interactions could be extracted from the transcriptomic responses, highly species-specific responses are suggested.…”

A glimpse of the endophytic bacterial diversity in roots of blackberry plants (Rubus fruticosus)

“…However, mutants with ACC deaminase activity, constructed by Sun et al (2009), were unable to promote root elongation in canola seedlings. Other well-studied endophytes, such as Azoarcus sp or Gluconacetobacter diazotrophicus, are also involved in promoting growth in diverse plant species, by fixing nitrogen within the plant tissues (Krause et al, 2006;Lery et al, 2011). Other direct mechanisms of plant growth promotion include the production of indole-acetic acid (IAA), siderophores, hydrogen cyanide, and proteases, and indirect mechanisms include the biocontrol of plant pathogens (Santoyo et al, 2012).…”