Soybean Ethylene Biosynthesis and Signaling: An in silico Approach and the Importance in Drought Stress

Ethylene (ET) promotes a so-called triple response in seedlings (thickening and shortening of hypocotyl and horizontal growth habit) and participates in abscission and stress responses. Due to the outstanding position that soybean crop occupies in the Brazilian economy, it was created the GENOSOJA (Brazilian Soybean Genome Consortium) to identify genes related to different biotic and abiotic stresses. Since the ET molecular mechanisms have been well elucidated in model plants, this present work described in silico the ET metabolic pathway in soybean genome using the GENOSOJA database. There were identified 502 genes related to ET that were divided into three groups (biosynthesis, signaling and transcription factors responsive to ET). In the proteins encoded by these genes there were identified conserved protein domains and orthology with proteic sequences belonged to the Arabidopsis thaliana and Oryza sativa, which was evaluated by BBH (Best Bidirectional Hit). Moreover, transcriptional regulation was studied by analysis of possible cis-elements present in the possible promoters, and differential expression was evaluated in the soybean transcriptome database under water deficit. Approximately 24 % of the genes characterized in silico were differentially expressed in the soybean transcriptome under drought stress. After validation of differentially expressed genes by RT-PCR and evaluation of the free ACC- ethylene precursor levels and ethylene production, it was possible to infer in silico models for ET biosynthesis and ET-mediated signaling, which allowed a better understanding in the molecular level of the importance of this phytohormone in soybean under water deficit (Supported by Embrapa, CNPq, CAPES, FAPDF, FAPEMIG).