From underground to sunlight: characterization of pif target genes define novel pif-regulated processes
- Autores: Arnau Rovira Freixa
- Directores de la Tesis: Elena Monte Collado (dir. tes.), Pablo Leivar Rico (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Salomé Prat (presid.), Irma Roig Villanova (secret.), Federico Valverde Albacete (voc.)
- Programa de doctorado: Programa de Doctorado en Biología y Biotecnología Vegetal por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
Plants perceive and integrate external (such as light and temperature) and internal (such as hormones or the circadian clock) signals to optimize growth and development in a changing environment. Light is used not only as a source of energy for plant photosynthesis, but also as a source of information to perceive the surrounding environment. Plants are armed with light sensitive proteins called photoreceptors that sense and transduce light signals to a core regulatory network that implements different facets of photomorphogenesis throughout plant life cycle. Studies in the model plant Arabidopsis thaliana have established that several transcriptional regulators such as the PHYTOCHROME INTERACTING FACTORS (PIFs) play a key role in this transcriptional network by regulating the expression of genes involved in different photomorphogenic processes such as seed germination, seedling deetiolation, diurnal and thermal growth, shade avoidance, or flowering. The downstream functions of this network and the implication of PIFs in other physiological and developmental responses remains poorly understood.
The main objective of this work is to expand current understanding of the regulatory network acting downstream of PIFs during photomorphogenesis, and to define novel regulatory roles of PIFs during plant development.
Previous studies had shown that MIDA9, a PIF3-regulated protein phosphatase 2C, regulates hook development during the post-germinative growth of the seedling. One of the aims of this thesis was to perform detailed genetic and phenotypic characterization of MIDA9 function, and we established that MIDA9 promotes the asymmetric growth required for the apical hook formation, possibly by altering ethylene biosynthesis.
A second aim consisted in the definition of a novel role of PIFs in regulating stomata movements under diurnal conditions. We propose that PIFs accumulate at the end of the night to induce the expression of a factor that is necessary to promote stomata aperture in response to light at dawn. Moreover, light is suggested to reduce bioactive levels of ABA (Abscisic Acid) and release the repression that this hormone exerts during the night.
Finally, we identified and characterized the function of KAT1 and MIDA9 as genes that modulate stomata movements downstream of the PIFs.
Because regulation of stomata movements is essential to control water balance in plants, the identified regulatory components are candidate molecular targets for the development of drought resistant plants. Moreover, the described regulation of the apical hook development might contribute to the establishment and survival of the postgerminative seedling.
