Identificación de un componente del sistema de endomembranas, atalix, implicado en la señalización del ayuno de fosfato en plantas
Author
Cardona López, Doris XimenaEntity
UAM. Departamento de BiologíaDate
2011-11-29Subjects
Plantas-Carencia en fósforo-Tesis doctorales; Suelos-Contenido en fósforo-Tesis doctorales; Biología y Biomedicina / BiologíaNote
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 29-11-2011Abstract
Phosphorus is an important nutrient for the growth of all organisms. Plants have
evolved throughout its evolution a rescue system involving developmental,
metabolic and physiological changes that allows them to adapt their growth
to phosphate (Pi)-poor soils. PHR1 (PHOSPHATE STARVATION RESPONSE 1) is one
of the key regulatory genes in controlling Pi starvation responses in plants.
In order to identify and characterize molecular mechanisms involved in
regulating PHR1 activity or that of its target genes, an EMS mutagenesis of phr1
mutant seeds was carried out aiming to identify mutants that suppress the phr1
phenotype. As a result, we isolated the Atalix mutant, which showed an
increase in the accumulation of anthocyanins and in the expression of PSI
genes (PHOSPHATE STARVATION INDUCED) under Pi deficient conditions
compared to phr1 mutant plants, suggesting that AtALIX acts as a negative
regulator in the response to phosphate starvation. Furthermore, we found that
Atalix alters the localization of PHT1 phosphate transporter and enhances Pi
uptake in a pho2 mutant background.
In addition, we cloned the AtALIX gene, that encodes a protein with a Bro1
domain that corresponds to the Arabidopsis thaliana ortholog of Bro1 (in yeast)
and ALIX (in mammals). These proteins are conserved in eukaryotes and play
diverse functions in controlling several regulatory and signalling processes, such
as endosomal sorting of transmembrane receptors, programmed cell death,
cytokinesis and control of transcription factor activity under specific stress
conditions. In this study, we found evidence of the involvement of AtALIX in
most of the above mentioned processes, mainly concerning the endosomal
system. In this context, studies with an active AtALIX-GFP fusion protein showed
that its localized in the cytoplasm and in small vesicles which likely correspond
to endosomes.
Together, our results suggest that AtALIX plays many different roles in
Arabidopsis, like its counterpart in mammals, probably acting as a scaffold
protein that brings together different regulatory proteins, including components
of the Pi signalling pathway. Actually, we demonstrated that AtALIX is a
modulator of Pi starvation responses as well as a component of the
endomembrane protein trafficking system.
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