Development of a system for high throughput screening of agrochemicals affecting plant growth behaviour
Machin, Franklin Qasim
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Why don’t crop plants grow as fast as they should? In optimal conditions, elite crop varieties routinely outperform those grown in the average field. The vast majority of this reduction in growth activity is due to abiotic stresses such as drought, heat, and nutrient limitation. Abiotic stress reduces plant growth by triggering a reduction of meristem size and causing premature differentiation of proliferating cells. Differentiated cells are no longer able to divide, and smaller meristems have a reduced capacity to restore growth when the abiotic stress passes. We have designed and evaluated a novel high-throughput screening system to identify compounds able to reduce or prevent this premature differentiation in order to retain modest growth capacity in stressful conditions and enable rapid recovery from stress. Such chemicals can be applied to crop plants using existing agricultural methods, and because there is no need for genetic modification, it is widely applicable to many different crop species. Using the novel technique of flow sorting followed by protoplast culture, we have developed a high-throughput automated confocal imaging method to screen chemicals for their effects upon cell differentiation. Meristem protoplasts isolated from the root tips of pROW1:GFP Arabidopsis plants were monitored for differentiation when exposed to different chemicals. To evaluate this system, a library of biologically active small molecules provided by Syngenta was screened against protoplasts and whole plants. Several compounds were identified with the ability to improve Arabidopsis root growth in in vitro growth conditions. Two subsets of these chemicals were identified: a subset of chemicals that improved stress tolerance through modulation of post-meristem differentiation, and a subset of chemicals that improve growth rate by increasing rates of cell division in the root apical meristem. This screening system is able to detect the subset of chemicals that was shown to affect postmeristem differentiation, but not the other subset. No false positives were detected. These results suggest that this single-cell screening system is a powerful, high-throughput method suitable for the detection of molecules for use in crop protection.