Javier Paz-Ares
Group Leader
Research summary
Plant responses to phosphate starvation represent an emblematic system for studies on regulation of gene activity. In plants, these responses involve both biochemical and developmental changes that improve Pi acquisition and recycling, and protect against the stress of Pi starvation. The induction of Pi starvation responses requires a sophisticated regulatory system that integrates information on external and internal plant Pi concentration, and on other nutrient content. Our aim is to contribute to the dissection of this regulatory system, which operates mainly at the transcriptional level but also involves post-transcriptional control.
Publications
Mohan TC, Castrillo G, Navarro C, Zarco-Fernández S, Ramireddy E, Mateo C, Zamarreño AM, Paz-Ares J, Muñoz R, García-Mina JM, Hernández LE, Schmülling T, Leyva A. Cytokinin Determines Thiol-Mediated Arsenic Tolerance and Accumulation. Plant Physiol 2016; 171(2):1418-2
Kalinowska K, Nagel MK, Goodman K, Cuyas L, Anzenberger F, Alkofer A, Paz-Ares J, Braun P, Rubio V, Otegui MS, Isono E. Arabidopsis ALIX is required for the endosomal localization of the deubiquitinating enzyme AMSH3. Proc Natl Acad Sci USA 2015; 112(40):E5543-51
Cardona-López X, Cuyas L, Marín E, Rajulu C, Irigoyen ML, Gil E, Puga MI, Bligny R, Nussaume L, Geldner N, Paz-Ares J*, Rubio V* (*corresponding authors). ESCRT-III-Associated Protein ALIX mediates High Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis. Plant Cell 2015; 27:2560-81
Thieme CJ, Rojas-Triana M, Stecyk E, Schudoma C, Zhang W, Yang L, Miñambres M, Walther D, Schulze WX, Paz-Ares J*, Scheible WR*, Kragler F* (*corresponding authors). Endogenous Arabidopsis messenger RNAs transported to distant tissues. Nat Plants 2015; 1(4):15025
Chen J, Wang Y, Wang F, Yang J, Gao M, Li C, Liu Y, Liu Y, Yamaji N, Ma JF, Paz-Ares J, Nussaume L, Zhang S, Yi K, Wu Z, Wu P. The Rice CK2 Kinase Regulates Trafficking of Phosphate Transporters in Response to Phosphate Levels. Plant Cell 2015; 27:711-23
Our research is focused on the phosphate (Pi) starvation rescue system of plants, a model system for studies of gene activity, with presumed biological potential in the context of low-input agriculture. In previous years, we identified transcription factor PHR1 as a master regulator of phosphate starvation responses in plants. In the last two years, we carried out functional analysis of the two PHR1 binding sites, previously detected in a ChIP-seq assay with PHR1. We also identified a component of the Pi sensing system, SPX1, and revealed its mode of action. Finally, we began the analysis of natural variation of transcriptomic responses to Pi starvation.
To study the function of P1BSI and P1BSII, the two binding sites used by PHR1 to regulate transcription of Pi starvation-responsive genes, we prepared artificial promoters consisting of four tandem copies of P1BSI or P1BSII upstream of the -45 minimal promoter from the 35S gene of CaMV. These promoters were fused to the GUS coding region. We found that the two binding sites, which are recognised by PHR1 in dimeric and monomeric forms, respectively, are bona fide Pi starvation-responsive elements, with P1BSI promoting the strongest response, in line with higher affinity binding by PHR1 (Figure 1).
We also identified SPX1, whose gene is highly Pi starvation-responsive, interacting with PHR1 as a component of the Pi sensing system. Indeed, SPX1 interaction with PHR1 is Pi-dependent both in vivo and in vitro, and causes inhibition of PHR1 binding to DNA. The high SPX1 accumulation during Pi starvation is considered to provide a mechanism for rapid shutdown of Pi starvation responses once Pi is resupplied.
In a study of natural variation of molecular responses to Pi starvation, we examined the Pi starvation responsive transcriptome of four ecotypes in addition to the reference Col ecotype, and found great interecotypic differences in Pi starvation-responsive genes. The CT ecotype showed the largest differences with Col (~1000 genes differentially expressed in CT vs Col in Pi-grown plants). At present we are performing transcriptomic analysis of 100 recombinant inbred lines from a ColxCT cross to identify expression quantitative trait loci corresponding to Pi starvation responsive genes.
