Caracterización del mecanismo integrador de señales de la respuesta de indol-3-acetamida y del desarrollo bajo condiciones de estrés abiótico en Arabidopsis thaliana

Abstract

Abiotic stresses greatly condition developmental processes in plants, and to decipher the growth-defense tradeoff phenomenon is key to understanding the fate of energy resources and their distribution to either defense or investment in development. Phytohormones are contributing to the regulation of this energy distribution and, among them, ABA is the phytohormone with the greatest influence on responses to abiotic stresses. On the other side, auxins are major growth factors in plants that drive virtually all aspects of plant growth. Hence, deeper insight into the crosstalk between auxins and ABA is fundamental to understanding the growth-defense tradeoff phenomenon. Auxin biosynthesis proceeds via a number of pathways. The indole-3-acetamide pathway is one of those routes. It is named according to its main intermediate, indole-3-acetamide, which is converted to indole-3-acetic acid by the virtue of AMIDASE1 (AMI1). In a microarray comparing ami1 null mutants with wild-type Arabidopsis, a significant proportion of the upregulated genes appeared to be associated with ABA responses. Amongst those genes, we found two myoblastosis protein (MYB) transcription factors, namely MYB74 and MYB102. In order to elucidate the molecular processes in which the two factors are involved, knock-out mutants of MYB74 and MYB102 were subjected to various analyses such as a drought, osmotic and salinity stress assays, phenotypic analyses of root architecture, as well as transcriptomics analyses and in silico analyses. Here, we roport the relation of MYB74 with drought resistance in Arabidopsis and its impact on the root system architecture. MYB102, in contrast, participates in seed development and in osmotic stress resistance in seedlings. In view of the fact that both factors do not entirely overlap in their functions although showing a large primary sequence identity, an in silico approach was taken in order to investigate the possible structural differences between MYB74 and MYB102, which could explain the functional differences of the two factors.