Expression of sugarcane genes induced by inoculation with Gluconacetobacter diazotrophicus and Herbaspirillum rubrisubalbicans

Abstract

Several Brazilian sugarcane varieties have the ability to grow with little addition of inorganic nitrogen fertilizers, showing high contributions of Biological Nitrogen Fixation (BNF). A particular type of nitrogen-fixing association has been described in this crop, where endophytic diazotrophs such as Gluconacetobacter diazotrophicus and Herbaspirillum spp. colonize plant tissues without causing disease symptoms. In order to gain insight into the role played by the sugarcane in the interaction between this plant and endophytic diazotrophs, we investigated gene expression profiles of sugarcane plants colonized by G. diazotrophicus and H. rubrisubalbicans by searching the sugarcane expressed sequence tag SUCEST Database (http://sucest.lad.ic.unicamp.br/en/). We produced an inventory of sugarcane genes, candidates for exclusive or preferential expression during the nitrogen-fixing association. This data suggests that the host plant might be actively involved in the establishment of the interaction with G. diazotrophicus and H. rubrisubalbicans.

Sugarcane Genetic Controls Involved in the Association with Beneficial Endophytic Nitrogen Fixing Bacteria

“…The data indicate that sugarcane plant does not behave simply as a silent host for the growth of these bacteria and actively participates in the association with endophytic diazotrophic bacteria (Urquiaga et al 1992;Nogueira et al 2001;Souza et al 2001;Vargas et al 2003). Nevertheless, the comprehension of how various sugarcane regulatory mechanisms are coordinated and connected to genotype and environmental signals, in order to control the establishment of a beneficial and endophytic type of association is still a big challenge.…”

“…In recent years, advances on the understanding of the role of sugarcane genes involved in the response to the diazotrophic bacteria have been achieved, mainly by studies of gene expression profiling. Database analysis of the sugarcane EST sequencing project (SUCEST) (Vettore et al 2003) revealed ESTs exclusively and preferentially expressed in G. diazotrophicus and H. rubrisubalbicans inoculated plants, which were functionally classified as members of several cellular and metabolic pathways (Nogueira et al 2001;Souza et al 2001;Vargas et al 2003) (Fig. 2).…”

“…Members of one important class of receptor protein, the RLKs (Receptor Like Kinase), were identified as candidates to be involved in sugarcane-nitrogen fixing bacteria association (Nogueira et al 2001;Vargas et al 2003;Vinagre et al 2006;Rocha et al 2007). Among the identified RLKs, SHR5 was the best characterized (Vinagre et al 2006).…”

History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

“…Since 1994, Dr. Hemerly's group from the UFRJ is addressing this question by investigating sugarcane gene expression during the association with Gluconacetobacter diazotrophicus using different approaches: (i) cDNA-AFLP fingerprinting, (ii) transcriptional profiles generated from the SUCEST (Sugarcane EST Sequencing Project) database and (iii) microarray. The novelty of this studies was to show for the first time that sugarcane might be actively involved in the association, because several genes involved in different plant physiological processes were identified as candidates to be differentially expressed during the association (Nogueira et al 2001). The group focus now the studies on the characterization of signaling pathways by which sugarcane plants can decipher bacterial signals and respond properly for a successful association (Vargas et al 2003); and the molecular mechanisms that promote plant growth by association with the endophytes.…”

Biological Nitrogen Fixation is not a Major Contributor to the Nitrogen Demand of a Commercially Grown South African Sugarcane Cultivar

“…The question which remains is whether these bacteria contribute significantly to the nitrogen budget of sugarcane, or whether the diazotrophic capacity of the bacteria merely enables their own growth in the high sugar environment that the endophytes are exposed to within sugarcane. Induction of sugarcane gene expression by inoculation with G. diazotrophicus and H. rubrisubalbicans may indicate active involvement of the plant in establishment of the interaction with the bacteria (Nogueira et al, 2001). However, it remains to be conclusively determined whether the reported gene induction is specifically for enabling the symbiosis, or merely a consequence of infection.…”