The Role of the Arabidopsis HYL1 Gene in Hormone Signaling

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Plant growth and development, as well as plant responses to stress, are orchestrated by several hormones. The action of the hormones within the plant and within individual cells depends on proteins that transmit the hormone signals to evoke both biochemical and transcriptional changes. This project has the objective of analyzing an Arabidopsis transposon insertion mutation, designated hyponastic leaves (hyl1), that alters the plant's responses to several hormones simultaneously. Preliminary evidence suggests that the mutant gene encodes a nuclear protein that binds to double-stranded RNA. Mutant plants are short, slow to flower, have curled leaves, produce few seeds, and have slow-growing roots that do not respond to gravity normally. Mutant plants show a reduced sensitivity to the auxin and cytokinin hormones and are hypersensitive to the hormone abscisic acid (ABA). Genetic and molecular experiments in the project are designed to understand how the protein encoded by the HYL1 gene participates in the plant's perception and response to different hormones. The importance of these experiments is that they will contribute to our understanding of how plants coordinate their responses to the multiple hormone signals that impinge on their cells. Although the experiments are being performed in the model plant Arabidopsis, knowledge gained in such a system can be transferred readily to crop plants because higher plants use the same or similar systems to regulate growth and stress responses. Such knowledge will be very important in future efforts to improve the ability of agricultural plants to maintain productivity under adverse conditions.