Caracterização da sinalização de auxina mediada por ciclofilina no controle das respostas adaptativas da raiz sob nutrição por nitrogênio em tomateiro (Solanum lycopersicum cv. ‘Micro-Tom’)

Abstract

The ability of plants to detect and respond to environmental factors, such as the availability of nutrients in the soil, influencing physiological plasticity and root architecture is controlled by local, cell-to-cell and systemic signaling pathways, via the phloem, coordinated by the expression of genes involved in adaptive root responses. Nitrogen (N) is an essential nutrient for plant growth and its heterogeneous distribution in the soil has led to the development of adaptive strategies that regulate its absorption and efficient use. Among these strategies are the induction of high-affinity transporters for N and changes in the root system. The diageotropica (dgt) mutant of tomato (Solanum lycopersicum) is defective in the CYCLOPHILIN1 (SlCyp1) gene, making it insensitive to auxin, a hormone that is fundamental for root organogenesis. As a result, the dgt mutant does not develop lateral roots. Previous studies have shown that SlCyp1 expressed in the aerial part can be transported to the root, where it influences the response to auxin and promotes the formation of lateral roots, suggesting its role in systemic signaling. In addition, its expression is induced by high light, linking light and root development. This study aimed to characterize SlCyp1 as a component of long-distance signaling in root adaptation under nitrogen-ammonium (N-NH4+) nutrition. To this end, Micro-Tom (MT) plants and dgt mutants were grown on media containing different concentrations of NH4+. Analysis of root architecture showed that NH4+ stimulates the initiation of lateral roots in plants with functional SlCyp1. To investigate the interaction between SlCyp1 and auxin, we analyzed the entire (e) and dgt entire (dgt e) mutants in the ENTIRE/SlIAA9 gene, a negative regulator of auxin response. Given that light affects local and systemic signaling, mutants in phytochromes A (phyA), B1 (phyB1), B2 (phyB2) and aurea (au), with only 5% of phytochrome levels, were studied to evaluate the involvement of light in the root response to N. In addition, reciprocal micrografting experiments between MT and dgt plants were conducted under different NH4+ conditions to determine whether SlCyp1 signaling occurs locally or systemically. The results showed that plants with MT in the shoot and dgt in the root developed lateral roots in the presence of NH4+, indicating the systemic action of SlCyp1. In addition, plants with a dgt shoot and MT root exhibited a typical MT root phenotype, suggesting that SlCyp1 also acts locally. In addition, the genetic interaction between DGT/SlCyp1 was demonstrated through the partial recovery of root development in dgt mutant plants and especially during ammonium nutrition. The results obtained here demonstrate that SlCyp1 regulates root development by modulating the response to auxin according to N availability, acting both locally and systemically in the root's adaptive responses.