Abstract
Sugarcane interacts with particular types of beneficial nitrogen-fixing bacteria that provide fixed-nitrogen and plant growth hormones to host plants, promoting an increase in plant biomass. Other benefits, as enhanced tolerance to abiotic stresses have been reported to some diazotrophs. Here we aim to study the effects of the association between the diazotroph Gluconacetobacter diazotrophicus PAL5 and sugarcane cv. SP70-1143 during water depletion by characterizing differential transcriptome profiles of sugarcane. RNA-seq libraries were generated from roots and shoots of sugarcane plants free of endophytes that were inoculated with G. diazotrophicus and subjected to water depletion for 3 days. A sugarcane reference transcriptome was constructed and used for the identification of differentially expressed transcripts. The differential profile of non-inoculated SP70-1143 suggests that it responds to water deficit stress by the activation of drought-responsive markers and hormone pathways, as ABA and Ethylene. qRT-PCR revealed that root samples had higher levels of G. diazotrophicus 3 days after water deficit, compared to roots of inoculated plants watered normally. With prolonged drought only inoculated plants survived, indicating that SP70-1143 plants colonized with G. diazotrophicus become more tolerant to drought stress than non-inoculated plants. Strengthening this hypothesis, several gene expression responses to drought were inactivated or regulated in an opposite manner, especially in roots, when plants were colonized by the bacteria. The data suggests that colonized roots would not be suffering from stress in the same way as non-inoculated plants. On the other hand, shoots specifically activate ABA-dependent signaling genes, which could act as key elements in the drought resistance conferred by G. diazotrophicus to SP70-1143. This work reports for the first time the involvement of G. diazotrophicus in the promotion of drought-tolerance to sugarcane cv. SP70-1143, and it describes the initial molecular events that may trigger the increased drought tolerance in the host plant.
Highlights
Sugarcane (Saccharum spp.) has become an important bioenergy crop worldwide
SP70-1143 colonized by the beneficial diazotrophic bacteria G. diazotrophicus, four different plant treatments were analyzed, following the pipeline presented in Figure 1A: i) plants in association with G. diazotrophicus and under normal watering conditions (GD); ii) in association with G. diazotrophicus and under water deficit (WD+GD); iii) non-inoculated and under normal watering conditions (CT); iv) non-inoculated and under water deficit (WD)
To confirm that plants were associated with G. diazotrophicus in a beneficial way before performing water deficit treatments, controls of bacteria colonization and of the increase in plant biomass were carried out
Summary
Sugarcane (Saccharum spp.) has become an important bioenergy crop worldwide. Its capability to store sucrose as a primary energy source, instead of more complex compounds as starch, proteins or lipids, makes its use for energy production easier. Statistical data from the Food and Agriculture Organization of the United Nations indicate that sugarcane production covered, in 2012, more than 26 million hectares worldwide, with a global production of 1,8 billion tons, representing a 30% of growth since the beginning of the century. As water availability is the major limiting factor for sugarcane productivity [1], studies that lead to an increase of sugarcane drought tolerance are needed to provide tools to allow sugarcane plantation in drier regions. This is one of the greater challenges for the sustainable expansion of sugarcane production that is being carried out in Brazil since 2007 [2]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call