"Root system development is an important agronomic trait. The right architecture in a given environment allows plants to survive periods of water of nutrient deficit, and compete effectively for resources. The identification of new components involved in the regulation of this process will allow, in the near future, to understand and manipulate plant development. Extensive research has shown that nitric oxide (NO) is a signalling molecule involved in several physiological processes during plant growth and development and also an important modulator of disease resistance. The present proposal is based on the following reasons:1. The use of genomic and proteomic tools has been a powerful approach to understand fundamental processes in plant development. We will apply the “-omics” technologies to the identification of new elements involved in the NO signalling network.2. One of the biggest challenges about the role of NO in plant signal transduction networks is the finding of real targets of NO. The nature of NO targets in plant growth and developmental processes still remains unclear. The identification of the elements that participate in these responses is, thus, essential to understand the NO perception and signalling within the seed and the seedling, which is a prerequisite for its genetic improvement.The hypothesis in this proposal is that nitric oxide (NO) acts in plant developmental processes through the interaction with other plant growth regulators, such as the phytohormone auxin, using similar molecular components.The main objective of this proposal is to get insight into the nitric oxide (NO) signalling network during root growth through genetic, proteomic and genomic approaches that may let to the identification of new components involved in the NO signal transduction pathway."