A Molecular Tool to Increase Protein Content and Broad Disease Resistance in Crops.

Crop plants must integrate signals from the environment and prioritize responses to stresses that may occur individually or simultaneously throughout the growing season. Stress responses can adversely affect plant growth and quality traits such as protein and starch. Deficiency in dietary protein is globally one of the most severe health problems; the ability to optimize protein productivity of plant-based foods has far-ranging impact on both world health and sustainability. Plant diseases each year cause major losses to crop production. We are developing a molecular tool that integrates higher protein content and broad-spectrum plant disease resistance in crops. The Arabidopsis thaliana Qua Quine Starch (QQS) orphan gene modulates carbon allocation to protein and starch. Ectopic expression of QQS increases protein content in soybean leaf and seed, in multiple high-/low-protein soybeans, corn and rice. QQS transcript levels are altered in plants under stresses and in mutants of genes involved in all sorts of stress responses, indicating that QQS may integrate primary metabolism with environmental perturbations, thus adjusting the plant’s adaption to abiotic and biotic stresses. The QQS protein binds to a transcriptional regulator in Arabidopsis and to its soybean, corn and rice homologs. Overexpression of the QQS interactor in Arabidopsis mimics QQS-overexpression phenotype, increasing protein content and decreasing carbohydrate. Mutants overexpressing QQS or its interactor have significantly increased resistance to plant pathogens. Our data reveal the core of a previously undefined network in which QQS participates and indicate QQS exerts its effect via an interaction with a transcription factor conserved across eukaryotic species; these findings open a new non-transgenic strategy to create high-protein crops and enhance crop disease resistance. Our research illustrates an example of translating basic research in Arabidopsis to major crop plants.