Cytosolic Glutamine Synthetase Is Modulated By Rust Infection and Nitrogen Status in Coffea arabica

Nitrogen (N) is the mineral nutrient most required by plants, and its limitation  directly influences plant development in natural and agricultural environments.  In coffee, one of the most important agricultural commodities in the world, N- fertilization represents one of the major costs on its cultivation. Several reports have shown that nitrogen-limiting conditions can impact on plant disease  development. The coffee rust, caused by Hemileia vastratrix, is considered the main disease in Coffea arabica. However, there are few molecular studies linking nutritional status of coffee plants and defense response to pathogens. Here, we evaluated the expression of cytosolic glutamine synthetase, CaGS1,
in plants infected with rust and under different N availabilities. C. arabica plants that are resistant and susceptible to rust were challenged with H. vastatrix, under N-starvation and N-sufficiency. Young leaves were collected 0, 12, 24 and 48h after inoculation. qPCR analysis indicated a transcript peak in 12h after inoculation, that is more pronunciated in N-sufficient leaves. Susceptible plants had a second expression peak at 48 h in N-starved leaves. Enzyme activity followed the same pattern of transcriptional responses. In this way, we can infer that cytosolic glutamine synthetase has been modulated by coffee rust and may be influenced by pathogen-host interaction, since the response was different between resistant and susceptible cultivars. The results allow an initial understanding of the molecular interaction between mineral nutrition and coffee rust. Finnancial support: Consorcio Pesquisa Café.