The genetic interaction between Azospirillum brasilense and maize during the inhibition of indole-acetic acid production by the plant

Maize is one of the most used plant species in human and animal food. For this reason, ways to increase its production without increasing the planted area are always necessary. One way of achieving this is by using plant growth-promoting bacteria (PGPB). Among the most well-know PGPB are the members of the genus Azospirillum, which have as main characteristics the ability to fix nitrogen and to produce phytohormones. This work aimed to better understand the genetic relationship between Azospirillum brasilense and maize during the inhibition of indole acetic acid (IAA) production by the plants. For this, the chemical compound Yucasin [5- (4-chlorophenyl) -4H-1,2,4-triazole-3-thiol], an inhibitor of one of the IAA plant-production pathways, was applied. Dual RNA-Seq was used to analyze the gene expression of the bacterium and maize using a combined analysis approach. With this methodology was possible to observe maize genes involved in the ABA response pathway being differentially expressed. Their pattern of expression suggested that the plant was responding to the presence of the Yucasin. Coding genes for the transcription factors MYB29 and WRKY71, involved in biotic and abiotic stress responses, were up-regulated in some experimental situations, indicating that the plant was responding to the presence of the bacterium and the Yucasin. Concerning the bacterial gene expression, genes involved in the transmembrane transport and terpenoid backbone biosynthesis were differentially expressed.