Identificação de fatores genéticos que medeiam o desenvolvimento da Síndrome de Evitação à Sombra (SAS) em resposta à disponibilidade de nitrogênio em 'Arabidopsis thaliana'

Abstract

For the efficient use of resources such as light and nutrients, plants exhibit developmental plasticity to better adapt their growth and development to variations in environmental conditions.The Shade Avoidance Syndrome (SAS) is a set of morphological changes that reduce the ability of plants to maintain reproductive success under suboptimal light conditions, such as shade. Although nitrogen (N) is an essential nutrient for plant development, the relationship between N nutrition and adaptive developmental responses to shade remains elusive. In this context, this work had the objective of caracterizing the molecular mechanisms involved in the development plasticity in response to shade in distinct conditions of inorganic N sources availability. The results sugest that the elongation of the hypocotyl in response to shade differs depending on the inorganic N source, with ammonium inhibiting hypocotyl elongation more strongly than nitrate. Experiments with loss-of-function mutants in the AMMONIUM TRANSPORTER genes demonstrated that ammonium translocation from the root to the shoot is a crucial factor in reducing hypocotyl elongation in response to shade. Through the activity of the HD-ZIPIII and KANADI transcription factor module, it was possible to verify that auxin is crucial for the N-dependent adaptive response to shade, and that ammonium promotes auxin entry into cells and simultaneously reduces efflux in epidermal cells, while nitrate increases auxin efflux in the epidermis. These results suggest that inorganic N sources modulate auxin transport differently, resulting in the adjustment of auxin levels in the hypocotyl epidermal cells and hypocotyl growth in shade. This study identifies inorganic N as a regulator of shade avoidance responses in Arabidosis, highlighting the complex regulation underlying processes in response to environmental fluctuations and nutritional status.