Transcriptomic Responses of Soybean to Phytophthora sojae Infection as an Approach to Understand the Prophylactic Role of Silicon

Silicon (Si) is known to have a beneficial role against many forms of biotic and abiotic stress, and more particularly against biotrophic fungi. Soybean production is greatly affected by Phytophthora sojae, a hemibiotrophic pathogen. In this regard, the objectives of this study were 1) to augment soybean resistance to P. sojae by exploiting its natural ability to absorb Si; and 2) to investigate the mechanisms by which Si could confer protection. The phenotypic response of soybean to P. sojae with (Si+) and without (Si-) Si was evaluated. Plants under Si⁺ treatment had a significantly higher survival rate and higher dry weight than control plants at 21 dpi. To understand the mechanisms inherent to Si prophylactic properties, RNA-seq analyses of soybean roots infected with P. sojae were performed over four time points of two treatments (Si+ vs Si-). Initial results show a differential activation of defense responses in plants under Si treatment at an early stage of infection (4dpi). Higher activation of Rps proteins in Si- plants, proteins known to activate effector-triggered immune (ETI) responses, suggests that Si has a role in preventing P. sojae effectors from reaching their target.