Abstract
BackgroundThe rapid growth of the world’s population demands an increase in food production that no longer can be reached by increasing amounts of nitrogenous fertilizers. Plant growth promoting bacteria (PGPB) might be an alternative to increase nitrogenous use efficiency (NUE) in important crops such wheat. Azospirillum brasilense is one of the most promising PGPB and wheat roots colonized by A. brasilense is a good model to investigate the molecular basis of plant-PGPB interaction including improvement in plant-NUE promoted by PGPB.ResultsWe performed a dual RNA-Seq transcriptional profiling of wheat roots colonized by A. brasilense strain FP2. cDNA libraries from biological replicates of colonized and non-inoculated wheat roots were sequenced and mapped to wheat and A. brasilense reference sequences. The unmapped reads were assembled de novo. Overall, we identified 23,215 wheat expressed ESTs and 702 A. brasilense expressed transcripts. Bacterial colonization caused changes in the expression of 776 wheat ESTs belonging to various functional categories, ranging from transport activity to biological regulation as well as defense mechanism, production of phytohormones and phytochemicals. In addition, genes encoding proteins related to bacterial chemotaxi, biofilm formation and nitrogen fixation were highly expressed in the sub-set of A. brasilense expressed genes.ConclusionsPGPB colonization enhanced the expression of plant genes related to nutrient up-take, nitrogen assimilation, DNA replication and regulation of cell division, which is consistent with a higher proportion of colonized root cells in the S-phase. Our data support the use of PGPB as an alternative to improve nutrient acquisition in important crops such as wheat, enhancing plant productivity and sustainability.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-378) contains supplementary material, which is available to authorized users.
Highlights
The rapid growth of the world’s population demands an increase in food production that no longer can be reached by increasing amounts of nitrogenous fertilizers
Bacterial counts showed that three days after inoculation root colonization reached 3.2 × 107 CFU per gram of fresh tissue (Figure 1), but no bacteria were recovered from surface sterilized roots indicating that the A. brasilense strain FP2 is an epiphytic colonizer
Simultaneous RNA-Seq analysis of wheat roots and Azospirillum brasilense To our knowledge, this is the first report of a dual RNASeq transcriptional analysis of plant-Plant growth promoting bacteria (PGPB) interaction
Summary
The rapid growth of the world’s population demands an increase in food production that no longer can be reached by increasing amounts of nitrogenous fertilizers. Plant growth promoting bacteria (PGPB) might be an alternative to increase nitrogenous use efficiency (NUE) in important crops such wheat. The global human population is projected to be 9 billion by 2050 To meet this rapid growth of the world’s population the predicted demand for food production must increase 1.7 fold by 2050 [1,2,3]. For the last 40 years crop production increased by 2.4 fold mostly promoted by a 7.4 fold increase in mineral N fertilizers application, which means that the N use efficiency (NUE) has declined 3.1 fold in that time [3,4]. In Latin America, hundreds of thousands of hectares have been inoculated with Azospirillum-based commercial inoculants, increasing grain yields of economically important crops such maize and wheat [5,6]
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