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Rice hormone response is involved in the temperature-dependent function of Xa7-mediated bacterial blight resistance

Stephen Cohen: Department of Bioagricultural Sciences and Pest Management, Colorado State University

<div><span face="Arial" style="font-family:Arial;">Bacterial blight, caused by </span><span face="Arial" style="font-family:Arial;"><i>Xanthomonas oryzae </i></span><span face="Arial" style="font-family:Arial;">pv. </span><span face="Arial" style="font-family:Arial;"><i>oryzae</i></span><span face="Arial" style="font-family:Arial;"> (Xoo)</span><span face="Arial" style="font-family:Arial;">, causes significant losses to global rice production. Bacterial blight disease is more severe during periods of high temperature. However, little is known about the underlying host molecular responses to pathogen infections during high temperature stress. Most known mechanisms of rice resistance to bacterial blight lose efficacy at high temperature, but, notably, one resistance gene, </span><span face="Arial" style="font-family:Arial;"><i>Xa7,</i></span><span face="Arial" style="font-family:Arial;"> functions better. To provide insights into how </span><span face="Arial" style="font-family:Arial;"><i>Xa7</i></span><span face="Arial" style="font-family:Arial;"> directs the host response at high temperature, we conducted a transcriptomics experiment. Plants exhibiting resistance at high temperature significantly down-regulated the abscisic acid signaling pathway, which is important to abiotic stress responses, while plants in a susceptible interaction did not. Intriguingly, the salicylic acid response – an important pathway in rice defense to Xoo – was down-regulated at high temperatures in all interactions, suggesting that enhanced </span><span face="Arial" style="font-family:Arial;"><i>Xa7 </i></span><span face="Arial" style="font-family:Arial;">activity at high temperature is independent of salicylic acid-mediated defense pathways. These results suggest that plants exhibiting </span><span face="Arial" style="font-family:Arial;"><i>Xa7</i></span><span face="Arial" style="font-family:Arial;">-mediated resistance prioritize response to pathogen over response to abiotic stress. This ongoing study is providing insight into the trade-off between disease resistance and plant productivity that will help in the development of rice varieties in a changing climate.</span></div>

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